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Author Topic: 4-400 Amplifier  (Read 41651 times)
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wx3k
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« Reply #25 on: December 30, 2008, 09:02:20 PM »

 Smiley Wow, thanks so much for the suggestions and really good information !!!!

Very cool ! I guess Ill have to start poking around some hamfests and find the grid and plate circuit components I need.

The Quintron is in good shape....I only thing I am a bit concerned about are the HV caps in the power supply. Would they be the oil filled variety that contain PCB's ? I have not pulled the cover on the power supply section yet to inspect it. Perhaps this would be a good idea.
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Stephanie WX3K
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« Reply #26 on: December 30, 2008, 09:09:56 PM »

Stephanie,

If the capacitors are oil-filled, just check the external condition.  If there is no leakage, they are safe, and will probably outlast you and me, whether or not they contain PCBs. 

Most, if not all, capacitors that do not contain PCBs are labelled "NO PCBs".  If oil filled, and no label as such, then they probably do contain PCBs.  But as long as they are not leaking, they really do not present a hazard. 

When inspecting the capacitors, make sure they have been mounted securely and are not chafing or wearing the paint off at the mounting points.  Also look for rust spots.  If there are no weak spots on the casing, they will probably not leak.

Oil caps can withstand a lot more abuse than electrolytics can.  Temperature variations and surges do not usually damage the oil caps, and they often self-heal if partially shorted.  So if they look good, keep em!

73,
Rick
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« Reply #27 on: December 30, 2008, 09:18:46 PM »

I echo Rick's advice and add to that if they ever leaked, even a small amount, you will see a sticky tan or brown wax like goop. It most likely will be near the porcelain high voltage insulators. Try not to worry if yours are clean. Your safe.

Mike
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« Reply #28 on: December 30, 2008, 09:54:58 PM »

I've never done it  but, it's been done....  how about using a hi voltage transformer  and hi power stereo amp to modulate the plate?
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N3DRB The Derb
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« Reply #29 on: December 30, 2008, 10:55:26 PM »

just curious.. what would a pair of 4-65's do?

modulated by ....say......hmmmm.....
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« Reply #30 on: December 31, 2008, 07:06:35 AM »

Smiley Wow, thanks so much for the suggestions and really good information !!!!

Very cool ! I guess Ill have to start poking around some hamfests and find the grid and plate circuit components I need.

The Quintron is in good shape....I only thing I am a bit concerned about are the HV caps in the power supply. Would they be the oil filled variety that contain PCB's ? I have not pulled the cover on the power supply section yet to inspect it. Perhaps this would be a good idea.


the power supply is a choke input after the FWB rectifier. IIRC they used a rather large choke and a rather small cap. IIRC, the cap is only 4 or 6 Mfd. It is also an oil filled cap. That rig is recent enough that it most likely WONT have PCBs. Mine had the "No PCBs" markings on the cap. Like everyone else says, dont worry about it if it has pcbs, if it's not leaking it is of absolutely no concern. I prefer the ones with the PCBs as this is a very good fire retardant.

And.......er.......furthermore.................PCBs only become a problem if injested, so dont lick the leaking seals or fry your eggs in the oil Grin Grin

                                                                       the Slab Bacon
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« Reply #31 on: December 31, 2008, 11:41:04 AM »

Oil caps... the other red meat!

I'll echo what Rick said, but also suggest that if you find worn paint or the beginnings of rust, fix those problems now. Don't be afraid to use a wire-wheel brush in a small drill for removing rust blisters, just remember the outer case is sheet metal so you don't want to apply too much inward force, just enough abbrasion to remove the rust. Grab yourself a can of gray enamel at Home Cheapo and spray it down, carefully masking the electrode insulators with a piece of paper (not with tape!), as well as masking the ratings stencils. Go ahead and patch up any worn-off paint while you're at it, as that will just become a rust spot later in life.

When you pull the caps out, you should immediately check for any oil slicks around their mounting rings. If you find any, inspect the bottom seam. Just a drop or two leaking out won't hurt, but you'll need to stop the leak. How to do so depends on the nature of the leak. Oil leaking out means the potential for moisture leaking in.

Don't be too paranoid about coming into contact with PCB oil, just use common sense. If you find an oil slick by touch, just give your hands a good warm-water wash with strong soap and you'll be fine.

PCB-oil caps usually don't explode, so the worst exposure you'll get is film from a leaking one. Non-PCB oil caps, on the other hand, are filled with mineral oil with a fairly low flash point, and no PCB to act as a fire retardant. They can get carried away if they short and the circuit isn't properly fused (or a breaker is defective), but that likely won't be a problem.
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flintstone mop
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« Reply #32 on: December 31, 2008, 11:44:08 AM »

WOW!
Steve, KL7OF, has a great idea!!!!!!!
That can be a very cheap way to go.
Power transformers easy to find! Info available on AMFONE for using a power tranny as a modulation transformer.
High powered audio amplifers everywhere!!
And for that nice low-end response a few chokes in series and a 2mf cap for the modified Heising hook-up and you're there.
I'm using the power transformer idea and some chokes in series for the Heising on an Elamc AF67 and those 6550's sound so nice.

GO FOR IT Stephanie........................
Fred
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wx3k
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« Reply #33 on: January 01, 2009, 05:03:03 PM »

I had my Ranger User Manual out the other day and was poking through it trying to understand it better. AB2EZ mentioned that he used an external modulator. I never realized that the octal plug on the back of the Ranger allowed you to do that.  Grin I have an EICO mono amp that I picked up from an estate that might be very suitable as a building block for this purpose. Ill have to investigate this later in my project.

Question: If one were to use an external high powered audio amp, what would be the level of "high power" in wattage we are talking about to modulate a 4-400 either through plate modulation or screen modulation ?
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Stephanie WX3K
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« Reply #34 on: January 01, 2009, 05:12:25 PM »

Re: PCBs......I feel better now  Smiley Thanks for the input guys.....I always de-ick my equipment with gloves. I have years of experience de-icking equipment. ;-)
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Stephanie WX3K
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« Reply #35 on: January 01, 2009, 05:18:31 PM »

Stephanie said:
Quote
had my Ranger User Manual out the other day and was poking through it trying to understand it better. AB2EZ mentioned that he used an external modulator. I never realized that the octal plug on the back of the Ranger allowed you to do

The Ranger is excellent. You can use it as a driver for the RF section, (should be able to drive a 4-400) and the speech amp/modulator can be used to drive your modulation tubes. I use mine to drive a pair of 813's in the RF and a pair of 810's in the modulation deck.
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« Reply #36 on: January 01, 2009, 10:09:19 PM »

Plate modulation: 300 watts (+/- depending on the actual plate input power).

Screen modulation: 20-50 watts but you'll only get about 100-150 watts  output compated to 300-400 out with plate modulation.



Question: If one were to use an external high powered audio amp, what would be the level of "high power" in wattage we are talking about to modulate a 4-400 either through plate modulation or screen modulation ?

I had my Ranger User Manual out the other day and was poking through it trying to understand it better. AB2EZ mentioned that he used an external modulator. I never realized that the octal plug on the back of the Ranger allowed you to do that.  Grin I have an EICO mono amp that I picked up from an estate that might be very suitable as a building block for this purpose. Ill have to investigate this later in my project.

Question: If one were to use an external high powered audio amp, what would be the level of "high power" in wattage we are talking about to modulate a 4-400 either through plate modulation or screen modulation ?
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w1vtp
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« Reply #37 on: January 12, 2009, 11:12:19 AM »

Stephanie

I agree with Thom's and other's comments on the oil-filled caps.  They will probably outlast us all.  I had a PS using them and the terminals were facing down.  There was a slight greasiness at the site of the caps.  I just kept the area clean with paper towels.  If you are worried about them, just start shopping around at the festers for a replacement.  The caps could then be turned in at a local haz mat outfit.  We have one here in Manchester.  You might be able to identify the properties of the oil by copying off all info on the caps themselves and checking around. 

Come to think about it -- wouldn't it be nice to have a national database for all PCB filled caps etc that we could check against?

Al VTP
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« Reply #38 on: January 12, 2009, 09:14:44 PM »

A long time ago, I was given 2 or 3 of the same transmittters.
I still have some parts.
Crappy stuff for an AM rig, the power supply was a bridge setup which I dont like, and light duty, the RF parts were a bit wimpy, and for higher frequencies, but I used 2 of the vacuum variables as neutralization caps in the push pull 812a rig, great for that! 3 to 30 pf mine were, and made adjusting the neutralization a snap, I put knobs on them pointing up.

You cant do much with a 10,000 volt 30 pf vacuum cap, but they make very nice (and small) neutralization caps.

I still have a power transformer and choke, and that RF plate choke with the pipe on it.
I gave one transformer and choke away to a local ham to use to power his art-13.

Kind of ugly iron....

Brett
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wx3k
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« Reply #39 on: April 03, 2016, 10:39:49 PM »

I am lighting up this message thread again.

Last year I acquired a 4-400 RF deck. Very nicely constructed.

I finally had a chance to take the bottom cover off the chassis. Well, I found a nice heavy duty filament transformer in there. I also found a full wave 5690 tube in there feeding the screen grids. The 5690 is capacitively coupled from the RF input.  Huh  RF drive biases the screen grids ? There appears to be no screen supply line feeding the 4-400s.


* File Apr 03, 10 26 56 PM.jpg (2588.96 KB, 4032x3024 - viewed 710 times.)
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Stephanie WX3K
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« Reply #40 on: April 04, 2016, 10:14:51 AM »

could be the notorious G2DAF circuit !   part of the rf drive is rectified and fed to the screens to dynamicaly bias the tube into operation ... seriously, I have heard the circuit work very well but most of the folks here do not agree (many harrumphs...)
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« Reply #41 on: April 04, 2016, 01:55:46 PM »


A decent write up on the topic here, called "Frinear":

http://pa0fri.home.xs4all.nl/Lineairs/FrinearPG400/fripg400.htm

"The screen grids in this amplifier are neither at a fixed high voltage nor at earth potential but at a voltage which is proportional to the RF drive. To that end, the RF input is transformed up 3 ÷ 1 in T1, rectified in a voltage doubler and applied to the four bypassed screen grids through individual resistors. This method is consistent with good linearity."

Jim
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« Reply #42 on: April 04, 2016, 05:28:55 PM »

 Grin Grin Grin  what Jim said

the advantage of the circuit is that tuned inputs are not needed for each band with as Varney claimed was similar distortion performance to grounded grid circuit... all I know is that Gene W5CBS ran a 4-1000 in this circuit on 40 mtr ssb, 1500W pep out and I listened both above and below Fc and his signal was clean with usual spectrum occupancy
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wx3k
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« Reply #43 on: April 04, 2016, 09:20:46 PM »

Wowie kazowie ! That is really awesome !  Grin

A very unique design for sure ! This is great because I made a whole set of assumptions about power supplies needed and it appears I dont need ALL that stuff. Coool Smiley
Thanks guys for the insight !



A decent write up on the topic here, called "Frinear":

http://pa0fri.home.xs4all.nl/Lineairs/FrinearPG400/fripg400.htm

"The screen grids in this amplifier are neither at a fixed high voltage nor at earth potential but at a voltage which is proportional to the RF drive. To that end, the RF input is transformed up 3 ÷ 1 in T1, rectified in a voltage doubler and applied to the four bypassed screen grids through individual resistors. This method is consistent with good linearity."

Jim
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Stephanie WX3K
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« Reply #44 on: April 04, 2016, 09:39:32 PM »

The "Frinear" is an adaptation of the old G2DAF design.  Depending on what tube was run, how the screen rectification and grid drive was set up, and how the amplifier was operated, a few people swore by them, and many swore at them.  They were not all clean.
Nowadays, with the availability of relatively inexpensive SDR receivers to use as ersatz spectrum analyzers, it would be easy to get a good idea of the IMD products in real time during operation.  There's nothing about the G2DAF circuit that couldn't be "backed out" if the results were not satisfactory and one decided to proceed with a more conventional topology.  I have a pair of 4X500s sitting around that I'd like to try with this circuit, and if it didn't make good IMD I would use the PureSignal correction in HPSDR to clean it up.  It's not first or even second on my priority list however.  I think G2DAF published his design sometime around 1960, using vacuum tube rectifiers.
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wx3k
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« Reply #45 on: April 04, 2016, 10:24:05 PM »

I say its worth at least the effort to fire the deck up in its current state for an initial evaluation at lower power levels Smiley

The "Frinear" is an adaptation of the old G2DAF design.  Depending on what tube was run, how the screen rectification and grid drive was set up, and how the amplifier was operated, a few people swore by them, and many swore at them.  They were not all clean.
Nowadays, with the availability of relatively inexpensive SDR receivers to use as ersatz spectrum analyzers, it would be easy to get a good idea of the IMD products in real time during operation.  There's nothing about the G2DAF circuit that couldn't be "backed out" if the results were not satisfactory and one decided to proceed with a more conventional topology.  I have a pair of 4X500s sitting around that I'd like to try with this circuit, and if it didn't make good IMD I would use the PureSignal correction in HPSDR to clean it up.  It's not first or even second on my priority list however.  I think G2DAF published his design sometime around 1960, using vacuum tube rectifiers.
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Stephanie WX3K
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« Reply #46 on: April 04, 2016, 11:28:18 PM »


A decent write up on the topic here, called "Frinear":

http://pa0fri.home.xs4all.nl/Lineairs/FrinearPG400/fripg400.htm

"The screen grids in this amplifier are neither at a fixed high voltage nor at earth potential but at a voltage which is proportional to the RF drive. To that end, the RF input is transformed up 3 ÷ 1 in T1, rectified in a voltage doubler and applied to the four bypassed screen grids through individual resistors. This method is consistent with good linearity."

Jim
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Cool Jim.

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