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Has anyone ever hooked up a transformer this way?




 
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Author Topic: Has anyone ever hooked up a transformer this way?  (Read 1164 times)
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K9MB
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« on: January 23, 2023, 03:36:19 PM »

I am working on a compact intermediate power GG 813x2 amp and I want to use an ANTEK 8t800 transformer for the B+
This transformer has two 800vac @500mA windings and I want to use bridge rectifier(s) to get about 2200vdc for the 813s

I have seen two articles on 813x2 amps using this tranny.
One hooks the 800vac windings in parallel and feeds a voltage doubler. (800x 2.8=2240vdc unloaded (1800vdc under load)
The second one hooks the 800vac windings in series to get 1600vac and feeds a bridge 1600 x1.4 =2240vdc (about 2100vdc under full load).

I am certain that the voltage doubler will “work”, but I hate the things in principle because they have poor regulation, so I want to avoid them…

The bridge is great, giving a nice stiff voltage, but hooking two 800vac windings buried in the toroid makes one nervous because even though ANTEK promises well over 3.5kv insulation between primary and secondaries, there is no spec between secondaries.

I figured out a possible way to hook up two 800vac bridge circuits and hook them in series and trying to find out if it has been considered elsewhere, I found the circuit below in a forum.

Has anyone else considered this arrangement to limit winding to winding peak voltages and avoid an arcing episode?
Opinions and suggestions desired- please… 73, Mike

PS: I had not thought of hooking to the center of the capacitor stack, but was planning to hook the negative of the second bridge directly to the positive of the. First one that has it’s negative at ground. Which way is best??
If I wanted half voltage (1100vdc) , I would hook that node to it’s own filter caps.


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W1ITT
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« Reply #1 on: January 23, 2023, 07:14:22 PM »

It might be worth a try to call Antek and see if you can find a good guy in the engineering department who would hipot secondary-to-secondary and give you an unofficial result.  Antek is a real company, so I suppose that their listed value includes a good safety factor.
Years ago, making high power/high voltage RF components, we had a DC Break...basically a 14 inch, 50 ohm, coaxial blocking capacitor that was rated and sold at 80 kv.  When the customer came for acceptance testing I took it to 80kv and held it for the required time.  The customer then wanted to see it go to 100 kv.  We made him sign the acceptance sheet so that he owned it and would have to pay for repairs if it smoked.  I ended up taking it to 150 kv..  He wanted to go even higher but I told him it was time for lunch and we weren't going further.  Period.  The point is that if you find the right person, things can happen.
73 de Norm W1ITT
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« Reply #2 on: January 23, 2023, 07:24:24 PM »

It is amazing that this question has been up all day and no one has made any suggestions, so I will offer my opinions.....  Edit:  Looks like either I type slowly, or Norm types faster!

The two bridge rectifiers connected in series, as in your drawing, are not really any better than putting the transformer secondary windings in series, and feeding one bridge rectifier.  The voltage across the secondary is the same in either case.  The only possible advantage is that the peak inverse voltage across each diode in bridges is half what it would be with a single bridge across both secondary windings in series.

I think the voltage doubler gets a bad rap because it is basically two half-wave rectifiers, with outputs in series, so the ripple, even though it is 120 cycles, is greater than that of a full wave rectifier.  But load regulation is not necessarily any worse.  It has that reputation because of the many cases where a transformer intended for a full-wave bridge is used in a doubler, thus doubling the load current, causing more heating in the transformer windings, thus offering poor output regulation.

Transformers designed for single wave doublers generally have larger secondary wire, thus lower resistance, and less voltage loss (and heat) than transformers designed for the lower current load of a bridge rectifier.

Single phase voltage doublers are commonly used for transmitter and linear amplifier supplies, because they can actually provide better load regulation than a center-tapped full wave rectifier, by virtue of only half as many turns on the secondary winding, allowing for larger wire size, and less voltage loss (heat).  But I actually prefer the full wave voltage doubler.  It requires a few more diodes, and a couple more capacitors, but it actually provides better voltage regulation, less ripple, and much less peak voltage on the transformer secondary than does the single phase voltage doubler.  Eight diodes, same number as two bridges, will do the job.  
The two Antek transformer secondary windings may be placed in parallel, providing a larger overall wire size, and less I2R loss (heat) than using them in series.  One other factor that affects the transformer efficiency (heat) is whether current is being drawn during each half cycle.  The center-tapped full wave rectifier uses each half of the secondary only half the time, thus the current during that time, for the same power, is double, yielding double the heat loss in the winding.  So it is best to use all the windings, all the time, for most efficient transformer performance.  The single phase voltage doubler does this, but at the expense of higher secondary peak voltage with respect to the primary and core, but the full wave voltage doubler does not.

I could not find my drawing of that circuit, but I located a similar one on AMfone here:  
http://amfone.net/Amforum/index.php?topic=25120.0
and I attached the relevant image to this post.  That other post may not provide the best explanation of the circuit, but it can be discussed in much more detail here.

The diagram shows a single output capacitor, but there is no reason two or more could not be used, with appropriate equalizing resistors, of course.

I used this circuit when rebuilding the HP-23A power supply for my SB-101, and it works very well.  Neither end of the transformer has more than the peak secondary voltage, with respect to primary or core, at any time.


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Rick / W8KHK  ex WB2HKX, WB4GNR
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« Reply #3 on: January 24, 2023, 01:27:20 AM »

Thanks Norm and Rick.
Well, I had to wait a while, but the advice does make food for thought.
Rick, that 4-8 full wave doubler is a fascinating circuit, and this 8T800 with the 800vac windings in parallel will have a low resistance (17-18 ohms).
I followed the links to an article that goes into a lot of detail on how the 4-8 works
It uses 5 half cycles to complete a circuit cycle and it seems to have the potential to outperform the doublers I see in commercial amps- I think- because I cannot be sure.
Fascinating circuit explained here:

http://rawfire.torche.com/~opcom/psu/4x8_power_supply.html


I admit that my attitude toward voltage doublers is based on prejudice and unfounded intuition and I have built a lot of bridges up with great success and they gave me at least 1.3 x rms voltage under full load.
Still- I am giving this some thought…You almost convince me, but I have ome more play on tje bridge idea, even though I seriously doubted that my Rube Goldberg double bridge was going to stress the windings any less than a refular series winding with a bridge.

Norm, I like your idea of making the call. The guy that used the 8T800min a series winding with a bridge said that he had called and received assurances that it was ok to do it and he had not had an arc over, as of publication.

I also discovered this sheet on the ANTEK listing for the 8T800 on Ebay, showing that the series winding was ok, or at least, it was illustrated.
See below:
Note that they specify that wires 2 and 3 are connected and the note at the bottom indicates polarity of windings. I do not know if this indicates a higher insulation for flash over or not, however, so I will make that call.
The circuit us in the top left corner.
73, Mike


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« Reply #4 on: January 24, 2023, 02:18:48 AM »

rawfire.torche.com is a site on which I was kindly allowed some space many years ago, glad to see Chuck's site is still up. So many have disappeared.

My current site (below) has the article with the simulation result. Good to have things in more than one place!
https://bunkerofdoom.com/lit/4x8/index.html
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« Reply #5 on: January 24, 2023, 07:59:52 AM »

I am also interested in the results of the call. I am using an 8T650 with the windings in series into a Harbach half wave doubler. I upped the specs on the caps to 390uf at 500V to give me a full 4kv rating on the cap bank. I get 3600V unloaded and 3250V loaded by the Drake L4B.

The thing that worries me is that the leads that come out of the transformer are rated at 600V even though the transformer is rated at 650V rms AC per winding. Not good.

What are your leads rated at? 600v for 800v windings is even more worrisome.

John
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AMLOVER
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« Reply #6 on: January 24, 2023, 09:50:31 AM »

Hi there,

I have done this exactly many many times and it works perfectly.
It is series connected of two or in my case more dc supplies.
The way you have designed it is the absolutely right one.
I have 5 different transformers and I connect them this way in order to get their total dc output voltage.
I can always decide how many of them will be activated from their primary side in order to get different output voltages.
Go on this and it will work very well, no doubt.
In your case however using one transformer with two secondaries I don't see any benefit to use two bridges.
It could also work well with the standard design, the secondaries in series (in the correct phase) and only one bridge.
With the today insulation material 1600vac is not a big deal. For sure the insulation of a today transformer will outstand it.


Stefano
 
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K9MB
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« Reply #7 on: January 24, 2023, 11:36:58 AM »

Thank you for the encouragement, Stephano.
I have used bridges in numerous center tapped transformers going back to old TV pulls and never had one melt down.

I was unfamiliar with the insulation in these new Toroids, but I just remembered where I saw the 813x2 amp that uses the 8T800 with the windings in series and a bridge rectifier.
The article is in the March/April issue of ER Magazine.

I have included a screenshot of the power supply circuit in this post.

ER Magazine is a fantastic resource for Construction of equipment and restoration.
Unfortunately, QST and CQ are more light operators magazines and QEX gets into stiff that is less interesting to guys on AM-fone.
Fortunately, the old issues of Ham Radio Magazine, QST, 73 and and QEX and other legacy publications are available online at World Radio History.com and Archives.org
Or the art would die out.

John, I wrote ANTEK a message, but have not heard from them. I may call them tomorrow.
73, Mike


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« Reply #8 on: January 24, 2023, 01:35:50 PM »

rawfire.torche.com is a site on which I was kindly allowed some space many years ago, glad to see Chuck's site is still up. So many have disappeared.

My current site (below) has the article with the simulation result. Good to have things in more than one place!
https://bunkerofdoom.com/lit/4x8/index.html

Patrick, I had not made the connection between you and Bunker of Doom.
Wow! Cannot tell you how many times that site has provided very useful and rare knowledge. Many thanks for your contribution to saving this stuff for the future.
73, Mike
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« Reply #9 on: January 24, 2023, 02:15:51 PM »

Mike, I looked at the Antek spec sheet for the 8T800 transformer, and it looks to me like you are good to go putting the secondary windings in series to feed a bridge rectifier.

Following is an excerpt taken from this link:
https://www.antekinc.com/as-8t800-800va-transformer/


"The 800VA toroidal transformers are commonly used in the high-end tube audio amplifier and RF transmitter. They have static shield between primary and secondary coils to improve the isolation and noise interference. This toroidal transformer has a very low magnetic leak. They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz. These transformers have heavier gauge wires then the normal requirement to avoid the copper lost during the full power output. The dielectric test is more than 3500V in between primary and secondary coils. Please see the test data for short circuit and open circuit. In most of the cases, this transformer can be output 20% more power from its rating at 60Hz power source without any problem. This transformer comes with 2 rubber pads and all mounting hardware."

The 3500 volt dielectric test would indicate to me that there should be no problem with 1600 volts into a bridge rectifier.  But after reading their text, I continue to wonder what they do with the "lost" copper!

It is interesting that they use larger than necessary wire for the windings, and that should help significantly with regard to dynamic voltage regulation.

You did not mention whether you are using an oil cap, or a bank of electrolytics.  Either should work well, but I have often seen too few capacitors in series for a comfortable voltage margin.  I know it hurts to lose more microfarads by adding more caps in series, but it is much better than seeing them fail in a chain reaction if one goes belly-up.  I do not believe a 5 or 10 percent margin is enough, but 20 or 30 percent makes me more confident.  Think of how much overvoltage is applied to the remaining caps if one becomes leaky, or fails altogether.  We cannot guarantee an equal voltage distribution based upon matched equalizing resistors, as that does not take into account different leakage, causing imbalance between the various caps.  For 3600 volts, I personally would not use less than ten 450 volt capacitors.

You mention laughing about bonehead moves, and your perfectly functional schematic with two bridge rectifiers in series reminds me of a perfectly innocent error, based upon lack of understanding, that was made by ME when I was six years old.  I had dad's battery charger, consisting of a variac, transformer, and a large selenium bridge rectifier, and I wanted more voltage.  Knowing that batteries in series produce additive voltage, I thought, why not series connect the output of two huge bridge rectifiers?  I proceeded to connect the input AC terminals of both bridge rectifiers in parallel, feeding both from the same transformer.  When I started to connect the rectifier outputs in series, well, let's just say it was more than spectacular.  Next came a theory lesson from dad, and another transformer to fix my error.  Lessons like that are not quickly forgotten, but there was no laughing, and no yelling.  Just part of dad mentoring, and I remember vividly how he stated that we learn more from mistakes and failures than we do from easy successes.
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« Reply #10 on: January 24, 2023, 03:46:52 PM »

The old GE Master Pro base station and repeater AC power supply had a +250 volt power supply and a second +400 volt power supply that were stacked with the 400-volt supply using the +250 volt bus as ground. Those things ran for decades without issues. I used them for external B+/HV power supplies for all type of radio projects and never had any issues. Will attach a picture.


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« Reply #11 on: January 24, 2023, 06:15:19 PM »

Mike, I looked at the Antek spec sheet for the 8T800 transformer, and it looks to me like you are good to go putting the secondary windings in series to feed a bridge rectifier.

Following is an excerpt taken from this link:
https://www.antekinc.com/as-8t800-800va-transformer/


"The 800VA toroidal transformers are commonly used in the high-end tube audio amplifier and RF transmitter. They have static shield between primary and secondary coils to improve the isolation and noise interference. This toroidal transformer has a very low magnetic leak. They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz. These transformers have heavier gauge wires then the normal requirement to avoid the copper lost during the full power output. The dielectric test is more than 3500V in between primary and secondary coils. Please see the test data for short circuit and open circuit. In most of the cases, this transformer can be output 20% more power from its rating at 60Hz power source without any problem. This transformer comes with 2 rubber pads and all mounting hardware."

The 3500 volt dielectric test would indicate to me that there should be no problem with 1600 volts into a bridge rectifier.  But after reading their text, I continue to wonder what they do with the "lost" copper!

It is interesting that they use larger than necessary wire for the windings, and that should help significantly with regard to dynamic voltage regulation.

You did not mention whether you are using an oil cap, or a bank of electrolytics.  Either should work well, but I have often seen too few capacitors in series for a comfortable voltage margin.  I know it hurts to lose more microfarads by adding more caps in series, but it is much better than seeing them fail in a chain reaction if one goes belly-up.  I do not believe a 5 or 10 percent margin is enough, but 20 or 30 percent makes me more confident.  Think of how much overvoltage is applied to the remaining caps if one becomes leaky, or fails altogether.  We cannot guarantee an equal voltage distribution based upon matched equalizing resistors, as that does not take into account different leakage, causing imbalance between the various caps.  For 3600 volts, I personally would not use less than ten 450 volt capacitors.

You mention laughing about bonehead moves, and your perfectly functional schematic with two bridge rectifiers in series reminds me of a perfectly innocent error, based upon lack of understanding, that was made by ME when I was six years old.  I had dad's battery charger, consisting of a variac, transformer, and a large selenium bridge rectifier, and I wanted more voltage.  Knowing that batteries in series produce additive voltage, I thought, why not series connect the output of two huge bridge rectifiers?  I proceeded to connect the input AC terminals of both bridge rectifiers in parallel, feeding both from the same transformer.  When I started to connect the rectifier outputs in series, well, let's just say it was more than spectacular.  Next came a theory lesson from dad, and another transformer to fix my error.  Lessons like that are not quickly forgotten, but there was no laughing, and no yelling.  Just part of dad mentoring, and I remember vividly how he stated that we learn more from mistakes and failures than we do from easy successes.

😂😂😂.
Ok, Rick- you got me in the revolutionary method you used to boost those Selenium  rectifier bridges…
I remember those old stack rectifiers in tv sets. Silicon rectifiers and later- schottkys would change everything- but that idea was better in your imagination than when implemented, either way…😉
I really wish that I had not done worse, but I did. I almost killed myself several times growing up either on my Honda motorcycle or on high voltage supply mistakes, but I will save that for another day….
Your Dad did well. He reminds me of my Uncle who employed me on his farm growing up. One day when I was 13, I was using his Tiller and the thing quit and would not start. I decided that I should take apart the carburetor and fix it and surprise him with my mechanical skills. I got it apart into about 30 pieces and then my fever cooled enough that I started into a panic because I was not sure how to put it back together.
While ai was sitting in the dirt in the barn, my uncle came in with his top hand and saw me, walked over, looked around and said calmly, “what are you doing Mike?”
I was praying for a quick death by this time and felt I deserved torture instead amd I said, “I was fixing the tiller”. He shook his head and walked away, saying over his shoulder to his assistant, “help him put it together”. Bad Eye Robertson guided me on how to assemble and adjust the carburetor and get it running and I learned so much that I was able to repair those engines all my life. My uncle never mentioned my mistake, but my gratitude for his not blowing his top and guiding me to learn makes me grateful to this day. Your Dad was such a Man and we are lucky to have had them there for us, Rick.

Anyhow, the plan is tentatively to stack 6-560uF @450volt electrolytics with resistors across them for my filter. Five times 450 is 2250 and the peak voltage is 1600 x 1.414 = 2262vdc
Six will give me about 18 percent more than minimum. I agree that a lot of headspace is best, specially with electrolytics. I may stack 8 in a 2x4 arrangement to allow 3 to fail… I over-design most things, so nothing new here. I still have 70uF if I stack 8 of them. What do you think?

One thing, though gives me a brain worm-a little.
My 2x4K amp will be powered by a 3400vac tranny in a bridge. This will give at least 4800 volts if I have 230vac on the primary, though this tranny has 4 taps and I will use the full primary to minimize the voltage.
Also, I have a 30Amp variac that will be in one leg of my 240volt line, so I can adjust the imput voltage from about 125vac to 250vac worst case.
My plan is to never bring,that,variac up more than enough to get 4500 volts out of my supply.
The question is this:
I have 3-10uF @5kV oil caps for my filter.
If I am always starting at bottom and bringing up voltage slowly, is 500volts head space enough for my oil caps. They are nice Bosch units and not old and no PCBs, etc.
I would never run this close using electrolytics, but figured oils will be ok with 10% head room. Is this reasonable?73, Mike
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« Reply #12 on: January 24, 2023, 06:29:59 PM »

The old GE Master Pro base station and repeater AC power supply had a +250 volt power supply and a second +400 volt power supply that were stacked with the 400-volt supply using the +250 volt bus as ground. Those things ran for decades without issues. I used them for external B+/HV power supplies for all type of radio projects and never had any issues. Will attach a picture.
Wow! GE Master Pro? That brings back memories. I never worked on a base station, but serviced a lot of repeaters with 4cx250 or 8122? Finals in the field. Plenty of opportunity to kill yourself while standing in mud and making sure the HV was killed…😉
I did mostly mobile radios and the Master II was popular in the late 70s with the discrete bipolar amps. What a noghtmare- those things had to go back to the shop bench!
My favorite old transmitter was a 39.5mhz low band base that,was an old Prog Line unit. It had a 100TH in the final and it was like a star in there when the mic was keyed. 😎 seems like it put out 100 watts FM on the low Band, though not sure after  40+years.
The most hated mobile radio by GE was the TPL. It was GE’s first attempt at usimg circuit boards and seems like they were phenolic. Total junk. The Master II seriesmwas much more reliable once you got the amp balanced and adjusted,
I also service old Motorola MOTRAN mobile radios. Fantastic radios. I field serviced them after scrapimg the dirt off. Seems like they used 5894s for the VHF band.
Got my start servicing mobile radios and repeaters. Life and tech has changed a lot since the late 70s. 73, Mike
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« Reply #13 on: January 24, 2023, 10:08:23 PM »

Well Mike, you bring back more memories from the distant, and recent past.
My dad hated having to try to start small engines that we had to mow the lawn with an electric reel mower.  I cannot remember how many times I ran over the power cord and had to stop and splice it AGAIN!  I learned about gasoline engines the same way you did, loved them.  I taught my dad how to deal with them, but he said that job was all mine.

As to the motorcycles, the bug bit me when I was stationed at Lowry AFB, Aurora CO.  I rented a Honda, took it up Mt. Evans, the highest paved roadway in the US, then the next day up to the top of Pike's Peak.  My wife did not want me to ride, but she departed company after 38 years of marriage, and that was my Cue to get a two-wheeler.  I got a 2006 Honda Shadow 650, then an additional bike, a new 2012 Yamaha 950 VStar, that sat in the showroom for a year, so I got it for half of list.  Rode both up until last year.  Never had a close call, but I took the safety course before starting to ride.  At 75, last year I decided I should no longer ride, due to weakness in my legs after years of chemo.  Both bikes sold, end of adventure.

Back to the power supply.  For your 2260 volt rig, 6 caps provide a 16 percent margin 2262/2700  at 93 uF, while 8 caps give you 37 percent margin at 2262/3600, and you still have 70 uF.  If you have them, and they fit in the enclosure, I would opt for the 8-pack.  With that margin, they will probably never fail, and run cooler.  An engineer would say use the minimum needed to get by.  The accountant would come along and subtract one, maybe even two.  But you are only building one rig, and you are the one to fix it, and clean up the mess if the caps go like a chain of firecrackers.  The difference between an optimist and pessimist?  Optimist sees glass have full, pessimist sees it half empty, while the engineer sees a glass that is 50% larger than necessary to hold the liquid.

To put it in perspective, I ran a pair of 4-400As in a linear I built in my barracks room at Davis Monthan in Tucson.  I used a UTC S-48 HV transformer, rated at 1300 volts, 500 mA, 650 VA output, where a choke input supply configuration was recommended.  I used a stack of HV diodes like used in the F4C Phantom radar, only needed four to make a bridge.  I fed it with a 10 amp variac from the 120 VAC line.  A 200 watt Kodak Photoflood bulb was in series for tune-up.  My filter consisted of four 14 uF 2000 volt GE Pyranol oil caps in series parallel, providing 14 uF at 4KV..  Not knowing better, and liking to live on the edge, I ran them up to the full 4000 volts, and ran the linear at 250 mA peaks, for 1KW indicated power input.  Even though the transformer center tap was intended to be grounded, no one told him, so he didn't complain.  Those capacitors were previously used by dad for a photography strobe light, charged slowly via an 816 MV tube, and discharged all at once, many times.  That supply never failed, all the components still working.  The amplifier build was May 1968.

I realize this is many fewer uFs than you plan to use, but all signal reports were excellent.  More might have given better regulation and a bit lower IMD, but never any hum reported.  More Ufs needed at lower voltage, as you are doing, but I believe 70 is more than enough.

The three 10 uF 5KV Bosch caps should do marvelous duty at 4500 to 4800 volts.  That is plenty of capacity at that voltage.  I do not know how the Bosch compare with the GE caps I used, so staying under the 5000 volt rating is good practice.  At least you do not have to worry about balancing the voltage across many capacitors in series.  The difference between 4500 and 4800 volts will not be heard or noticed at the receiving end, and the variac lets you avoid going above 4500.  If one cap shorts due to overvoltage, the end result WILL be heard at the receiving end.  Need I say more?

PS  I have not forgotten your request for more info on my Frankenstein T-60, and will get around to sharing more soon.
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« Reply #14 on: January 25, 2023, 12:19:08 PM »

Well Mike, you bring back more memories from the distant, and recent past.
My dad hated having to try to start small engines that we had to mow the lawn with an electric reel mower.  I cannot remember how many times I ran over the power cord and had to stop and splice it AGAIN!  I learned about gasoline engines the same way you did, loved them.  I taught my dad how to deal with them, but he said that job was all mine. -

As to the motorcycles, the bug bit me when I was stationed at Lowry AFB, Aurora CO.  I rented a Honda, took it up Mt. Evans, the highest paved roadway in the US, then the next day up to the top of Pike's Peak.  My wife did not want me to ride, but she departed company after 38 years of marriage, and that was my Cue to get a two-wheeler.  I got a 2006 Honda Shadow 650, then an additional bike, a new 2012 Yamaha 950 VStar, that sat in the showroom for a year, so I got it for half of list.  Rode both up until last year.  Never had a close call, but I took the safety course before starting to ride.  At 75, last year I decided I should no longer ride, due to weakness in my legs after years of chemo.  Both bikes sold, end of adventure.

Back to the power supply.  For your 2260 volt rig, 6 caps provide a 16 percent margin 2262/2700  at 93 uF, while 8 caps give you 37 percent margin at 2262/3600, and you still have 70 uF.  If you have them, and they fit in the enclosure, I would opt for the 8-pack.  With that margin, they will probably never fail, and run cooler.  An engineer would say use the minimum needed to get by.  The accountant would come along and subtract one, maybe even two.  But you are only building one rig, and you are the one to fix it, and clean up the mess if the caps go like a chain of firecrackers.  The difference between an optimist and pessimist?  Optimist sees glass have full, pessimist sees it half empty, while the engineer sees a glass that is 50% larger than necessary to hold the liquid.

To put it in perspective, I ran a pair of 4-400As in a linear I built in my barracks room at Davis Monthan in Tucson.  I used a UTC S-48 HV transformer, rated at 1300 volts, 500 mA, 650 VA output, where a choke input supply configuration was recommended.  I used a stack of HV diodes like used in the F4C Phantom radar, only needed four to make a bridge.  I fed it with a 10 amp variac from the 120 VAC line.  A 200 watt Kodak Photoflood bulb was in series for tune-up.  My filter consisted of four 14 uF 2000 volt GE Pyranol oil caps in series parallel, providing 14 uF at 4KV..  Not knowing better, and liking to live on the edge, I ran them up to the full 4000 volts, and ran the linear at 250 mA peaks, for 1KW indicated power input.  Even though the transformer center tap was intended to be grounded, no one told him, so he didn't complain.  Those capacitors were previously used by dad for a photography strobe light, charged slowly via an 816 MV tube, and discharged all at once, many times.  That supply never failed, all the components still working.  The amplifier build was May 1968.

I realize this is many fewer uFs than you plan to use, but all signal reports were excellent.  More might have given better regulation and a bit lower IMD, but never any hum reported.  More Ufs needed at lower voltage, as you are doing, but I believe 70 is more than enough.

The three 10 uF 5KV Bosch caps should do marvelous duty at 4500 to 4800 volts.  That is plenty of capacity at that voltage.  I do not know how the Bosch compare with the GE caps I used, so staying under the 5000 volt rating is good practice.  At least you do not have to worry about balancing the voltage across many capacitors in series.  The difference between 4500 and 4800 volts will not be heard or noticed at the receiving end, and the variac lets you avoid going above 4500.  If one cap shorts due to overvoltage, the end result WILL be heard at the receiving end.  Need I say more?

PS  I have not forgotten your request for more info on my Frankenstein T-60, and will get around to sharing more soon.

Rick,
I have to hand it to you. I rode into my 20s and after getting married stayed with the van or my Suburban.
My Uncle Glen rode all his life and was in a Honda club that toured all over the country. It is the only way to ride “safely”, because people who drive cars either do not see bikes or figure they do not rate the normal respect one deserves on the road.
Actually, in college, I rode in a bicycle club on 10 speed peddle bikes and they are really dangerous unless you know what you are doing. These days, there are a lot of bike paths and lanes, but I got literally blown off the road aomce by an 18 wheeler hauling coal, who missed me by 2 feet and was going over 70.
I had some close calls on my 305 Honda too. I woke up in a cold sweat for several years reliving some close ones… I was full of ice water while it happened and only got the shales later. Funny how time slows down in those situations, bit it is essential to be out there. Still- I loved it and remember a lot of great rides with friends in a group of 4 or more staggered. With those guys, we got space and respect and nobody cut us off.
I laughed at your Dad hating lawn mower engines. As a youth, I was a gear head and loved getting dirty, but as an old man, I hate getting grease on me. I still service my Troy-bilt tiller with that venerable Tecumseh T60 engine that I bought in 1982. It still starts on one pull in the spring, except two years ago. They don’t make tjose great cast iron engines any more. I am forced to repair my Yanmar YM165D tractor too and my ZTR, because mechanics are not around that can service them.
Last time I rebuilt a real carburetor was in 1982 when I rebuilt a two barrel Holley on a Dodge Omni.
I still have a dwell meter and feeler gauges somewhere, but do not own anything olde enough to use them. It might be why I love Venerable old tubes and big iron for Radio. When I was 30, I had the bases of at least 50 tubes memorized, but most young people never heard of any of them… Glad a few other old Geezers remember it and even use that knowledge, even though my grid is leaking these days in my Class C memory…😉

Yes, I am definitely going with 8 of the 560uF @450volt caps. They are new ones and more compact than the older aluminum ones. With 8, I only have 250v across each.
I was just thinking this morning that I bought some surplus plastic caps that are 16uF or so and high voltage. Three or 4 of those in parallel might be better and they are fairly compact. As you said, 70uF is overkill and 32uF is plenty for my 2260 supply.
I just bought the Bosch caps and they look very good. I think that I have a box full of either 4 or 8uF oils in my RV Garage and they are 5kv too. May be GE brand and no pvcs in them, though as long as,they do not leak, probably mot a issue anyhow.
Your pushing your oils to the ledge gives me confidence that my 500 volt headspace is adequate. As you say, the difference between 4500 and 4800 volts in a 2x4K rog is insignificant anyway. The plan is to run the tubes at about 1kw each out (2kw total) so,the 3rd order products are way down. Tom advised me about this because the IMD is -35dB or so, at 1000 watts per tube and -30dB at 1500 watts per tube.
The 2x813 gg amp is to drive the 2x4K amp both on SSB and on AM linear.
The plan is to drive the 813s with about 20 watts from my FLEX5000A and get 100 watts AM linear to drive the 2x4Ks to 500-600 watts carrier output and 2000 watts pep with modulation. The FLEX can give me -35 to -38dB IMD and hopefully, the 813s can give -35dB run at 100- 200 watts out to drive the big jugs.
The IMD output of the amp is never better than the driver or intermediate amp.
The goal is not to make enemies of my neighbors on the band… I credit Tom for helping me see this factor. In the deep past, I just troed to load my amps for maximum and then cut back mic gain so, the meter current stayed less than half the maximum and ask buddies to listen around the frequency for,splatter.
Of course, when splatter appears, you have already lost the war. New SDR receivers that have built in panadapters allow one to see distortion products that many may not even notice.
I have never been an appliance operator interested in plugging in a radio amd talking only. The design and construction of the stiff is the real fun in it. Guys like Tom inspire me because they keep pushing the envelope and other guys have built a lot of stuff and their advice is priceless.
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« Reply #15 on: January 25, 2023, 06:07:34 PM »

I ran a 5kv GE cap with a 4kv xformer, FWB.

Yes, 6.2kv on the cap.

I don't recommend this at all.  An amp came in for a freshilening up.  Tested the cap, esr was low.  Didn't think the original builder would 'extend' the ratings like that, but he did.

That dn capacitor is still in the amp and working!

I asked the original builder, he built the amp in the early 90s.  So it's got some miles.

500v headroom on an oil filled is fine.

Just be mindful of the summer / winter dryer outlet voltage difference, though with the vatiac you have that figured out.

--Shane
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« Reply #16 on: January 25, 2023, 07:04:02 PM »

😂😂😂.
Well, Shane, I thought that Rick was pushing hi 4kv cap at 4kv, but your guy lays him over completely. 😉
I was worried a little about only 500 volts headspace, but running a cap at -2.2kv is insane…

The guy was obviously suicidal with that Chernobyl overload😉😂😂
Wheww- I would not want to be in the shack if that thing arced over…

I need to say, though- I have never been able to get by with this kind of thing.
I have seen guys put up antennas that would not last a week at my house, but they stay up through violent windstorms and ice for these guys. On the other hand, if I do not over design a thing- it will go down in a gentle breeze.

Reminds me of my youth- when my little brother (I was eldest) got into anything or broke something, I got into trouble. I would say- “it was he that did it, not me” .
The answer? “He does not know better, but you do and should look out for him”.
I used to think it was just Dad, but then when I built anything or put up an antenna, it had to be done with strong supports and well waterproofed with tension relief on feedlines…

Bottom line. At least 500volts headroom is minimum on 5k caps.
Thanks for sharing.
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« Reply #17 on: January 25, 2023, 08:59:38 PM »

Mike,

Yes to all your comments about riding safety.  A group of cyclists are hard to miss.  When not riding in a group, I tried to stick to the rural two-lane roads.  Problem with the four-lanes is the fact that so many people try to thread the needle, switching back and forth without looking first, that is scary.  One of my good friends at HP was killed by a wild pickup driver doing just that, and Mark was on a Gold Wing.

I had a Troy Built Horse for many years, but I hated the Tecumseh, it was always hard to start.  I was given a Honda engine that fit perfectly and was quieter, so out went the T.  Now my brother is gardening with the horse.  I do not mind getting greasy at all, but working on the engine under the hood gives me a backache.  And why do I need to pull the throttle body and the entire induction system from my Nissan Maxima 3.5L just to service the spark plugs and coils?  When I serviced it, I found two different makes of plugs, three in the front were easy access, and a different brand than the inacccessible back bank.  What does that tell you?

Back to the focus of this thread, Yes, I believe you will be happy that you used all eight of the caps.  Which is better, 8 units, working conservatively, or two good spares on the shelf?  Good for what?  Just the look of a bank of 8 is so much better than a six-pack.

Two linears in cascade, each running well below their headroom limit, always provide much better IMD performance.  Tom went even one better, and used the best IMD-rated tube for the intermediate amplifier, I believe it was something like a 4CX350.  For the intermediate amplifier, I prefer a grid-driven class A, as opposed to a cathode driven stage.  I am wondering if a pair of 813s is overkill for the intermediate stage, but if ya got em, run em.

I have a Hermes Lite II which I plan to use as a receiver and a VFO for the AM rig, providing true transceiver tuning convenience.  If you can zero-beat the received signal, then you are on the net frequency.  But now I am actually considering the construction of a solid-state linear for that rig, based upon a recent design of WA1QIX.  It will throw a lot of heat, but that ain't all bad this time of year!  I am so tired of many nights in the low 20s, and living near HotLanta, that should not be happening.  I live in the SOUTH!

So many projects, so little time.   If I could get finished with the final version of the Audio Processor project, and get the artwork verified, I could spend uninterrupted time on the 4CX3000 Class-A series modulated rig.  Talk about a shack heater, that will be 100 percent efficient in turning dissipation into cozy shack warmth!  I am thinking that modulator will be paired up with a couple Eimac 304-TLs in push-pull.  They will work well at 2KV, and provide good modulation headroom with a 5000 volt supply!

By the way, I recall Ray, KA3EKH, and AMLover both commented on stacking the rectified and filtered outputs of multiple HV secondary windings.  Yes, that is very common, and if you look at the early Tektronix 500 oscilloscopes, in fact all the way through the 535, 535, and 555, they all stacked the regulated outputs to provide the many voltages needed in the instrument.  If it worked on the communication equipment, and the Tek instruments, it must be A-OK.
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« Reply #18 on: January 26, 2023, 12:32:43 AM »

Rick,
Sorry that you did not bond with Tecumsehs. I have only had this 6hp T60 and maybe I got lucky.
I did have a problem one year when I forgot to drain the tank and carburetor bowl and the alky-gas corroded my jets and after fighting and cleaning with mixed results I got a chinese knockoff and installed a shutoff valve and a filter in the line, plus I was able to find a source for gas without alcohol and all has been smooth since that ethanol us hydroscopic and rots traditional fuel systems… not a fan! 🙄

I saw Steve’s post on the stack of 11cN90s as a linear for AM.
It was something he had prototyped, but have seen nothing else since.

I am using the 813s because they are tough and I have at least a couple of dozen of them I have accumulated. I will run a pair with 2200 volts and load them to about 120-140mA so I get 60- 70 watts carrier to drive my 2x4K rig on AM linear. If I get 25% efficiency the two 813s will be dissipating about 90-120 watts each on carrier, so they do not overheat. 60-70 watts should drive the 2x4k amp to 4500 volts at 400mA or about 2kw input and about 500 watts carrier output. The goal is 2000 watts peak with modulation I think.
The 4-1000a tubes will be dissipating about 750 watts each on carrier only.
Lots of heat- just like Steve’s FET amp! 😉.
On SSB, I would load the 813s to put out 300 watts and drive the 2x4k amp to 3kw out- peak theoretically, though Steves says 1200 per tube is cleaner, so maybe 250w from the 813s and 2500 from the 4-1ks on SSB and hope to get -35dB 3rd order IMD or thereabouts…
I always dream big and plan long and adapt as I go.…

By the way, I just remembered that I bought some 30uF at 6kv caps that were made for defibrillators in hopes of using them for hv supplies.
Do you know anthing about them?
I have attached a picture and tech data for thebones I have. They are rated at 10,000 cycles on defibrillators, but why not use them as filter caps?
Ant comments?
Very compact and they use oil and polyurethane powder, I think.
73, Mike


* 1E266BCF-EA9A-42EE-978A-10B55D449450.jpeg (492.42 KB, 2465x1570 - viewed 17 times.)

* 7F0C5384-7EA5-42A7-BB12-0466F3DCE878.jpeg (160.42 KB, 1705x1519 - viewed 17 times.)
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« Reply #19 on: January 26, 2023, 12:34:50 AM »

Interesting thread.

Mike and Rick:

All of this is very worthwhile.  Remember that the average station is running about 200 watts pep output SSB.  (my estimate)  If you run 2000W pep output, then you have to be 10 dB cleaner than the average station JUST to blend in with the 200W crowd.  Otherwise you will start to stick out and get complaints.... especially if at -25db 3rd IMD or lower.  This is like running a real world -25dB 3rd 2KW pep rig effectively producing -15 dB 3rd. (relative splatter)

Anyway, in the future, we will all probably switch to adaptive pre-distortion / Pure Signal SDR technology. The old school amplifiers like we are talking about will become instantly clean by using it. But for now...

Running the 813s in grid driven, class A service:  Compared to a pair of 813s in GG with regulated screen voltage (built in NFB) it may be a wash.   But take a grid driven pair of 813s in class A1 with additional RF NFB around it -  and the class A would win.   But more heat with the class A and an additional stage of RF for the NFB loop.

The super linear system I built about ten years ago used the 100 mW FT-1000D pre-pre-driver, (-70dB 3rd)  into a 1 watt class A lab amp, (-70dB 3rd)  into a class A  3CX-350J at 50 W (special linear purposed tube) (-55 dB 3rd)  into an 8877 running class A, (-55 dB 3rd)  and into a pair of 8877s.   At "low power" 1500W output it was showing a spectacular  -55dB third order. The RF tuning was critical to get -55dB 3rd.  I usually parked it in the DX window on 75M . A fast tuneup would yield about -45dB 3rd.  That is one clean amplifier system. Actually matched pre-distortion / Pure Signal stuff when tuned carefully with a tone and spec analyzer before each use.

Mike, if you have a stiff regulated screen voltage on the 813s and 4X1s, you should do FB.   But remember that the 813 and 4-1000A were not designed for linear service like the newer 3-500Z, 3CX-1200, etc..  But they do very FB in linear modulator service at audio frequencies.    The extra -10dB 3rd using careful cleanliness techniques can turn the 813/4X1 into a decent amplifier. (using GG, regulated screen voltage, reg grid bias, very low grid current and heavy C2 plate loading)     Clean drivers are critical. The result can never be better than the dirtiest driver stage in the whole chain.

It's not easy to break the -30 dB 3rd IMD barrier without some extra effort.    Look at the modern ham solid state amplifers going for $7K ++.  They are still hard pressed to beat the modern tube linears.  I thought by now we would have PDM linears, but that didn't happen in the ham world.  What saved our ass is SDR adaptive pre-disortion instead. I can always tell the stations running pre-distorton by their sharp skirts.  It's like when spark gap rigs were getting shamed by the new tube continuous wave DC rigs in about 1920 (~ 100 years ago) .... and finally outlawed in 1934.

Tom, K1JJ
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« Reply #20 on: January 26, 2023, 01:10:15 AM »

Interesting thread.

Mike and Rick:

All of this is very worthwhile.  Remember that the average station is running about 200 watts pep output SSB.  (my estimate)  If you run 2000W pep output, then you have to be 10 dB cleaner than the average station JUST to blend in with the 200W crowd.  Otherwise you will start to stick out and get complaints.... especially if at -25db 3rd IMD or lower.  This is like running a real world -25dB 3rd 2KW pep rig effectively producing -15 dB 3rd. (relative splatter)

Anyway, in the future, we will all probably switch to pre-distortion / Pure Signal SDR technology. The old school amplifiers like we are talking about will become instantly clean by using it. But for now...

Running the 813s in grid driven, class A service:  Compared to a pair of 813s in GG with regulated screen voltage (built in NFB) it may be a wash.   But take a grid driven pair of 813s in class A1 with additional RF NFB around it -  and the class A would win.   But more heat with the class A and an additional stage of RF for the NFB loop.

The super linear system I built about ten years ago used the 100 mW FT-1000D pre-pre-driver, (-70dB 3rd)  into a 1 watt class A lab amp, (-70dB 3rd)  into a class A  3CX-350J at 50 W (special linear purposed tube) (-55 dB 3rd)  into an 8877 running class A, (-55 dB 3rd)  and into a pair of 8877s.   At "low power" 1500W output it was showing a spectacular  -55dB third order. The RF tuning was critical to get -55dB 3rd.  I usually parked it in the DX window on 75M . A fast tuneup would yield about -45dB 3rd.  That is one clean amplifier system. Actually matched pre-distortion / Pure Signal stuff when tuned carefully with a tone and spec analyzer before each use.

Mike, if you have a stiff regulated screen voltage on the 813s and 4X1s, you should do FB.   But remember that the 813 and 4-1000A were not designed for linear service like the newer 3-500Z, 3CX-1200, etc..  But they do very FB in linear modulator service at audio frequencies.    The extra -10dB 3rd using careful cleanliness techniques can turn the 813/4X1 in a decent amplifier. (using GG, screen voltage, very low grid current and heavy C2 loading)  It's not easy to break the -30 dB 3rd IMD barrier without some extra effort.    Look at the modern ham solid state amplifers going for $7K ++.  They are still hard pressed to beat the modern tube linears.  I thought by now we would have PDM linears, but that didn't happen in the ham world.  What saved our ass is SDR pre-disortion instead.  I can always tell the stations running pre-distorton by their sharp skirts.  It's like when spark gap rigs were getting shamed by the new continuous wave DC rigs in about 1920.    ~ 100 years ago.

T

Hi Tom,
😂😂😂
Wow, you just made me think of my best shot at low 3rd order IMD as equivalent to a rotary gap spark tramsmitter compared to a fleming valve oscillator stabilized by a quartz crystal…😳😬😬😂😂
Seriously, thanks Tom, just saw your email. Will definitely go AB1 GG with about 300 regulated volts on the screens and a switched stack of bias diodes to set my operating point for best performance as a driver.
The 2x813s will be a dress rehearsal fir the 2x4Ks setup, which will be parallel.
This SDR predistortion thing is new to me. Just downloaded a paper on it and will peruse, though it will not stop present plans for my best (-35dB 3rd order) performance by a Luddite Neanderthal-one step from a rotary spark gap generator…😉.

Also, I have to say that you did all the old linear technology could hope for in that string of class A amps amd -55dB sounds amazing to this ole cave man geezer.
I should have guessed that you had already travelled to the rim of the earth in that journey.
The fact is that power is not the biggest thing for me, but getting 500 clean watts of carrier on AM linear sounds fun. I appreciate your counsel- as always, Tom.
73, Mike.
PS: Hey- what about these defibrillator caps. Any knowledge on them? MB
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« Reply #21 on: January 26, 2023, 11:58:42 AM »

Hi Mike,

The Flex, Anan and probably some of the "kit" SDR rigs have adaptive pre-distortion software and capability by now. ("Pure Signal," etc)  Just sample some RF off the final amplifier output (using a toroidal transformer) and feed it back to the low level SDR rig.  Commonly done.

The good thang is no matter what linear chain you build now, you can easily turn it into a pristine -55 dB 3rd machine later on using this technology.  Even a nasty 600 watt solid state RF amp can be used as a driver in this case.


For now, you will probably do better using a single 3-500Z as a driver for the two 4X1s in linear.  That's what I am using here now... Last year I built up "Baby Blue,"  a single 3-500Z linear with 1.5 to 3KV on it. (HV Variac controlled)    The driver needs to be cleaner than the final amp and this does the trick. Later on, I will bias them harder for better efficiency and run adaptive pre-distortion.  I admit the 813s are more romantic.  

Remember to include a bias setting into cutoff class C to run "linear AM".   That really works well.  The AM carrier provides the "bias".   It will not work on ssb class C...

* I have no experience with the defibrillator caps. Seems like a repeat of the photo flash caps.  I've  used photoflash caps here for years. I'll bet someone here from industry knows if defibrillator caps will hold up.   10,000 cycles seems a lot, but what if you T/R key the HV supply like I do?   A soft step-start will probably help lifespan.

BTW, with 6KV @ 32 uF, I'm really surprised there are not a lot of defibrillator electrocutions reported in ER rooms or at nursing homes using them.  I mean, even a common ham 2KV @ 20 uF power supply can take you out....  They must be current limited and well insulated.


T
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« Reply #22 on: January 26, 2023, 01:25:04 PM »

Hi Mike,

The Flex, Anan and probably some of the "kit" SDR rigs have pre-distortion software and capability by now. ("Pure Signal," etc)  Just sample some RF off the final amplifier output (using a toroidal transformer) and feed it back to the low level SDR rig.  Commonly done.

The good thang is no matter what linear chain you build now, you can easily turn it into a pristine -55 dB 3rd machine later on using this technology.  Even a nasty 600 watt solid state RF amp can be used as a driver in this case.


For now, you will probably do better using a single 3-500Z as a driver for the two 4X1s in linear.  That's what I am using here now... Last year I built up "Baby Blue,"  a single 3-500Z linear with 1.5 to 3KV on it. (HV Variac controlled)    The driver needs to be cleaner than the final amp and this does the trick. Later on, I will bias them harder for better efficiency and run pre-distortion.  I admit the 813s are more romantic.  

Remember to incude a bias setting into cutoff class C to run "linear AM".   That really works well.  The AM carrier provides the "bias".   It will not work on ssb class C...

* I have no experience with the defibrillator caps. Seems like a repeat of the photo flash caps.  I've  used photoflash caps here for years. I'll bet someone here from industry knows if defibrillator caps will hold up.   10,000 cycles seems a lot, but what if you T/R key the HV supply like I do?   A soft step-start will probably help lifespan.

BTW, with 6KV @ 32 uF, I'm really surprised there are not a lot of defibrillator electrocutions reported in ER rooms or at nursing homes using them.  I mean, even a common ham 2KV @ 20 uF power supply can take you out....  They must be current limited and well insulated.


T

Thanks Tom,
Ok, I will leave off using the 813s, but I may make an overlay of a couple for my front panel…😉.
I actually have a 800 watt 1100-1700 vac tranny that will pit out 400mA in a bridge, so I can get 1500 or 2300volts by just switching the tap and will not need a 10 amp variac…

It came out of some medical equipment, I think. The secondary was 70 ohms I think for the 1700 full winding. I found data somewhere that it was 800va, so figured the winding was rated about 450-500mA.
I have a pair of Eimac 3-500z pulls that a guy told me were full power in a SB220.
Have not checked them yet, but I read his message on the internet, so it has to be true-right? 😬😉😂

Wow, that sample and clean SDR idea sounds great. I do hope that someone figures out how to make my FLEX-5000a do that. I love the open system it has, so maybe some genius can figure that out.
I have always loved panaceas!!🤓😉😂😉
73, Mike

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« Reply #23 on: January 28, 2023, 03:47:53 PM »

interesting topic.  I enjoyed the GE references esp the old TPL (known officially as Transistorized Progress Line.  Unofficially as toilet paper line) I really liked the Mastr Pro receiver modules for single freq. work

As to the Antek toroids.  I think the assembly techniques are the same across the product line.  We had discussed this several years ago here on the forum when I raised my potential objection for placing hv secondary windings in series.  I still think it is a bad idea since if the secondary windings are bifilar wound with only the winding 'varnish' between them for insulation!

Having no experience with Antek qc they have ok'd the series connection in their drwg J-01255 and have green lighted this practice - so who knows?

Left up to me and having taken one of these toroid xfmrs apart I would stack several lower power hv supplies limited by the 3500 volt spec.
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Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
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« Reply #24 on: January 28, 2023, 06:44:27 PM »

interesting topic.  I enjoyed the GE references esp the old TPL (known officially as Transistorized Progress Line.  Unofficially as toilet paper line) I really liked the Mastr Pro receiver modules for single freq. work

As to the Antek toroids.  I think the assembly techniques are the same across the product line.  We had discussed this several years ago here on the forum when I raised my potential objection for placing hv secondary windings in series.  I still think it is a bad idea since if the secondary windings are bifilar wound with only the winding 'varnish' between them for insulation!


Having no experience with Antek qc they have ok'd the series connection in their drwg J-01255 and have green lighted this practice - so who knows?

Left up to me and having taken one of these toroid xfmrs apart I would stack several lower power hv supplies limited by the 3500 volt spec.

Hi John,
Thanks for the advice on the ANTEK toroids. There seems to be a lot of opinions on it. The guy that published the ER articel on a 2x813 rig hooked them in series and said he had used them for some time.
Reminds me of the lyrics of a song that was written and recorded in 1947, a year before I was born.

Smoke That Cigarette written by Merle Travis and Tex Williams-

Written by Merle Travis and Tex Williams
“Now I'm a feller with a heart of gold
And the ways of a gentleman I've been told
The kind of guy that wouldn't even harm a flea
But if me and a certain character met
The guy that invented the cigarette
I'd murder that son-of-a-gun in the first degree

It ain't cuz I don't smoke myself
And I don't reckon that it'll harm your health
Smoked all my life and I ain't dead yet”

The lyrics tell it all. A man knows that what he sets out to do could go very wrong, but he does it anyway, and if he escapes a while, he justifies it by saying, he has done this ill-advised thing a long time and it hasn’t killed him yet…😉😂😂😂

Luckily for me, I just figured out another way to do this thing.
I remembered that I had a Varian insudtrial high voltage transformer that has two 120vac windings in the primary and a single secondary that is 1850vac with a tap at 1180vac
I measured the windings and the secondary was 68 ohms (42 ohms for the 1180 tap)
The core measurements calculate the iron to be rated at 750VA.
I,also decided to go with a single 3-500z and run 1650vdc on it at 400mA. The datasheets say it will give me over 350watts on SSB full carrier and the 3rd Order IMD is rated at -46dB.
The entire purpose of this amp is to take 20-40 watts from my FLEX5000a and give me enough power to drive a 2x4k gg final running AB1 that will hopefully give me -35dB 3rd order at about 1500 watts out on SSB and 500 watts carrier on AM Linear operation.
The idea is to make fewer enemies while putting out full legal power by making it as clean as possible.
The 1180 winding should give me 450mA out easily at 1650volts dc and that is how I plan to run it as a super clean intermediate power amp and driver.
That us the plan today amyhow…🤪

Yes, the TPL were pure dung in my mind. I used tomtake hookup wire to strap the circuit board traces, which would break and cause intermittent open circuits and angry customers. We were  taking them out of service and junking them when I left GE. The Master Pros were great radios, but then they got “smart” and brought out the Master II series…nice radios except the 100 watt mobile  had 4 discreet bipolars that had to be balanced or they would not work and we were spreading coils to get them going. They had a 25 watt mobile that was a nice reliable mobile,though.
I started designing receivers and transmitters forvwildlife studies after that and lost track…
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