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Author Topic: Schematic Check Print 813 Deck  (Read 64642 times)
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KB7HTV
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« Reply #75 on: May 04, 2011, 01:46:28 PM »

Yes there is a number on it, I  thought it would be buried in the annals of obsolescence. I will write it down and post it tonight. I did not notice last night if the end bells come off, if they do I could get some idea of wire size in the winding looks big enough to handle 350Ma or so.
Plate current on the single 813 is about 180ma. The modulator I have not looked up yet but it is not a constant load.
My relays are only good for 10A. need to get one good for 20A to switch the primary of the HV transformer.
Still digging through the junk boxes looking for parts, making a list, hope to make headway this coming weekend.

Dale
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« Reply #76 on: May 04, 2011, 01:47:01 PM »

Quote
my ohmmeter has a inductance setting said 23 henrys

What is the brand name of that meter? I need one that will do hennry's.
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KB7HTV
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« Reply #77 on: May 04, 2011, 01:55:40 PM »

Resistance of the Choke
the resistance of the winding is 83 ohms
and the winding to the case is open

Dale
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KA2DZT
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« Reply #78 on: May 05, 2011, 09:18:59 PM »

Yes, those RF chokes on the grids of the 8000's are small VHF parasitic suppressors. I believe I used about 10 turns of #24 wire wrapped around a high value 1 watt resistor. I believe their value is something like 0.2 uH. One other small correction - all the meters are shunted by a 0.01 uF capacitor.

And Jim, I forgot to credit you for giving me the idea to try the diode isolation circuit in the bias supply. So far it has worked very well. As I said, the grid circuit is metered for continuous reading of both current and voltage. They are both very stable during transmission.

Ron

Ron,

I like the grid bias supply circuit you're using with the diode isolation.  I guess Jim WD5JKO came up with the idea of the diode, credit to Jim.

It seems that the grid resistor offers a load on the supply, which is good.  I think the full grid bias is developed through the grid resistor without regard to the bias supply.  I guess the grid voltage would be greater than the bias supply voltage at full drive current.  If the grid drive drops, grid leak voltage drops,  the bias supply maintains a minimum voltage on the grid.  Seems like it should work.

I'll have to try this circuit.  With triodes you need some sort of fixed bias to protect the tube.  With screen grid tubes, using a clamp tube circuit on the screen voltage also works well.

Thanks for sharing the circuit.

Fred
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« Reply #79 on: May 06, 2011, 01:37:12 AM »

Peter:  I am using a B&W JEL 160 grid coil which has no center tap, and the wire is so fine and wound so closely, that it would be very difficult to add one. So I simply applied the grid bias voltage to the end of the coil instead and it sems to work fine. I also have a JCL160 coil that has a center tap and fixed center link. But since the tubes are in paralel, not push pull, I thought the end link coil would be more appropriate. I always thought the link should be at the lowest RF potential spot on the coil. This would be in the center for a balanced push pull circuit, or at the end for a non push pull arrangement. In any event, it works.
Fred: My understanding is he same as yours. With no grid drive, the bias supply supplies cutoff voltage. With grid drive, all the bias is grid leak. When I apply filament power, I see about -100V on the grids. With grid drive but no plate voltage, I see about -450V. With grid drive and plate voltage, the grid voltage drops to about -350V, just where the book says it should be. Maybe I'm just lucky, but so far it has worked very well. Cheesy

Ron
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« Reply #80 on: May 06, 2011, 10:12:13 AM »

Ron, if it works it works! it's just that I've never seen unbalanced linking
tuned by a split-cap with rotor grounded. It almost looks like a pi-net
input.

I wonder, maybe one of the experts can chime-in here, could this kind of
grid tank help with tubes of high input capacitance (like, say, the 4D32) ?

73 de Peter
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« Reply #81 on: May 07, 2011, 01:59:49 AM »

Peter,
Your post started me thinking and doing some research both here in the forum archives and in my reference books. It seems that you are right - a center tap grid coil is recommended whenever the grid circuit is balanced (which it is when grid neutralization is used with a pi network plate tank circuit). Since I do have a center tapped coil available, I'm gonna give it a try and see what, if any, changes occur. I'll let you know what happens.
Ron
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KA2DZT
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« Reply #82 on: May 07, 2011, 03:08:57 AM »

Dale,

Any luck on digging out the choke and seeing if there are any numbers on it??

Waiting to hear,

Fred
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KB7HTV
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« Reply #83 on: May 07, 2011, 01:45:44 PM »

Meters

weston 505
weston 506
simpson IS-129 model 125
no text as to internal resistance
 
Choke numbers
21210
138552

Hope to work on the radio today and try to redraw the schematic this weekend



* 102_4325.JPG (467.59 KB, 2048x1536 - viewed 787 times.)
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KA2DZT
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« Reply #84 on: May 08, 2011, 04:02:20 AM »

Dale,

OK on the meter numbers, those are style type numbers.  You should be able to use the meters,  probably you'll have to use the 10ma meter for your grid current.  You'll have to shunt it with a small resistance equal to the resistance of the meter.  Not hard to do, just measure the terminals with a digital ohm meter and find a resistor equal to that amount and connect it across the meter.  The meter will then read 0-20ma, 10ma reading will be 20ma.

OK on the choke,  looks like it may be OK for transmitter service (just maybe).

The numbers don't tell much, except the 138 number is a manufacturer's code.  The 138 code is for Chicago Transformer.  The choke was made by Chicago for some other manufacturer of equipment. The last three digits are a date code, the last digit of the year (0-9) the last two are the week of the year (01-52).  These codes were used between 1940-1960. But, as you can see, no real way to know what decade the part was made, but, most of these codes were from the 1950's. The other number set has very little meaning, except Chicago did use those 5 digit numbers on some of their chokes to tell the ratings.  Example, Chicago's standard-catalog-model choke 12hy@105ma carried a number, stamped into the steel case, of 12105.

If we try to use that same method for your choke number 21210,  That would mean the choke is 21hys@210ma.  Problem is 21 henries doesn't make any sense because of the 80 ohm resistance you measured. A 21hy choke of that size would have much more resistance.  Double check the number because a number of 12210 could easily be what that choke is, 12hy@210ma.  If the 21210 is correct, then it's just a part number that usually can't be located in any Chicago catalog.  Only Chicago and the manual of the piece of equipment the choke was made for would have the ratings.

I would suggest that you try to find a better choke, one that was designed to run at high voltage with at least 300ma.  If you are going to use the step-start to turn on the HV supply on transmit, you need a high inductance input choke to limit the in-rush current, especially with those high capacitance electolytics.

In most all other cases, xfmrs and chokes that have 5 digit part numbers (no letters) are special units that were made by a transformer manufacturer for some other maker of equipment.  This is true for most all transformer manufacturers.  The manufacturer's code number did not always appear on the parts.

Fred
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KB7HTV
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« Reply #85 on: May 08, 2011, 12:51:46 PM »

is it possible to separate the power supplies for the modulator and the transmitter after rectifier stage or does that cause problems
I have seen transmitters and modulators with separate power supplies  in the handbooks from the fiftys.
The henrys measurement I took was with my vom that has a lc meter
there are 2 little wire grabbers recessed into the front of the meter
so you have to solder some solid hookup wire leads to the coil being measured.
the meter is made for measuring small leaded components, and it was kinda bouncing around when I took the measurement. I have never really trusted it for big components, I wanted to be able to take this to swapmeets looking for capacitors and transformers.
Today is punch and mount the clamp tube day maybe do some filament wiring.

fine buisness on the meters may not even bother with the screen current, like you say, you cant really change it anyway.

there is a swapmeet next weekend, I will see what is there.

Dale
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KA2DZT
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« Reply #86 on: May 08, 2011, 01:13:59 PM »

Dale,

As you were making your last post I added some additional comments about the choke in my previous post that you may want to go back and read.

Most will tell you that it's better to use one power supply for both the 813 PA and the modulators.  I agree, You would never want one supply to turn on and have the other supply to fail to turn on.  Especially, the modulators being on without any high voltage on the 813 PA.  No PA load on the mod. xfmr will quickly arc the mod xfmr.  Better to use one supply for both.

Fred
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« Reply #87 on: May 08, 2011, 09:50:12 PM »

Hi Dale,

I have a nice NOS Triad choke, model number C-19A. Looks new. 10Hy, 300mA, 3000V test. It's yours for the price of shipping if you think it might help.

Peter: I put in the new center link/center tap coil and it also works fine. As far as I can tell, there is no difference in the tuning of the grid tank with the new coil. I'm gonna stick with the center link coil since that seems to be the consensus opinion of how to do it. I made a couple of other changes to the circuit as well. I took the second 254W out of the circuit so that I could get a larger spacing on the neutralizing cap. It was only about 1/8 inch spacing with both tubes, now it is about 1/4 inch. With both tubes, I was only running the plate current at 200mA anyway. With one tube, I can run about 180 mA, so I havent lost much power. 1800V @ 180mA - 325W input and about 225W output.  There is one added bonus - Now that I have one tube running at full plate current, there is a faint red glow that brightens with modulation. Nice visual effect. Smiley Lastly, I raised (lowered) the grid voltage to -400V after reading some archived comments and suggestions from K4KYV. All the changes appear to work FB.

Ron
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KB7HTV
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« Reply #88 on: May 08, 2011, 11:53:36 PM »

Ron

That's a fine offer Ron, take it in to UPS have em weigh it and cost it out I will send you the money

Thanks

Dale
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KA2DZT
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« Reply #89 on: May 09, 2011, 01:59:44 AM »

The Triad choke that Ron offered would be a good one to use.  I've found that Triad transformers are some of the better ones.  I have a 500ma 10hy Triad and it does a good job at filtering.  A lot of folks may be surprised to know that some of the worst chokes IMO are the UTC S line.  In contrast the UTC PA series chokes are some of the best.  UTC CG series are also good.  Early Thordarsons are good.  One of the last series Thordarson made (21 series) are fair.  Most any of the Stancors are good,  they made the same chokes throughout their history.

I have about a 1000 transformers and chokes (counting the small ones) hanging around and have been working with them for nearly 50yrs.

I'm not sure if the Triad is rated at 3KV or 2KV. I've seen Triads that were only rated 2KV.  BUT, you must understand what that rating really means.  Those ratings are the RMS TEST VOLTAGE.  As a rule, to find the DC voltage the choke will handle you must subtract 1KV then divide by two.  So a choke that is rated at 3KV RMS TEST is really only good for about 1KV DC.  Some chokes are rated at some "DC voltage working".  You can use the choke at the full DC working voltage.  Some chokes are rated at some "voltage insulation" not really sure what the manufacturer really meant by that rating.

You can probably run the Triad at a MAX of about 1200V-1500V tops.  Just think, if it fails and shorts, you'll be the first one to know Grin.

There is more stress on an input choke than there is on the second choke in a two stage filter circuit.

A lot of folks will tell you that you can insulate the choke from ground (chassis) to avoid it shorting.  Forget that, it's stupid and dangerous.  You can put the choke in the negative lead which greatly reduces the high voltage on it. Check any Handbook to see how that's done.

Insulating any choke or transformer from ground is a dangerous thing to do, even though it's talk about and done by many.

Fred
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KB7HTV
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« Reply #90 on: May 09, 2011, 12:44:10 PM »

Fred,

What can I expect the efficiency of the HV transformer to be?
 Initially, I have to run 1250V at the moment so using the tube tables

The RF deck can be estimated to draw 160Ma (.160 X 1250V. = 200W input)

The Modulator deck is said to draw 260Ma peak.
so  for RMS .707 X 260 is 183ma
and we do not need 200 watts of audio so we can derate that and be conservative for a single 813 so say 100Ma

so total is 260Ma average
IXE=Watts
.260 x 1250 = 325W

W/E=I or 325/120=2.7A
* est 60%    2.7/.6 = 4.5A

fuse at 5 amps 120VAC (my relays may work)

what about the ground path back thru the chassis rack etc.
what about my number #4 copper going to a couple of ground rods
from the rack and the aluminum rack base of the power supply rack
I understand the 2 wire model  of having the choke in the return path.
but now Ive gone an mucked up my understanding of this given my setup.

Dale
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KA2DZT
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« Reply #91 on: May 10, 2011, 03:52:46 AM »

Fred,

What can I expect the efficiency of the HV transformer to be?
 Initially, I have to run 1250V at the moment so using the tube tables

The RF deck can be estimated to draw 160Ma (.160 X 1250V. = 200W input)

The Modulator deck is said to draw 260Ma peak.
so  for RMS .707 X 260 is 183ma
and we do not need 200 watts of audio so we can derate that and be conservative for a single 813 so say 100Ma

so total is 260Ma average
IXE=Watts
.260 x 1250 = 325W

W/E=I or 325/120=2.7A
* est 60%    2.7/.6 = 4.5A

fuse at 5 amps 120VAC (my relays may work)

what about the ground path back thru the chassis rack etc.
what about my number #4 copper going to a couple of ground rods
from the rack and the aluminum rack base of the power supply rack
I understand the 2 wire model  of having the choke in the return path.
but now Ive gone an mucked up my understanding of this given my setup.

Dale


Dale,

The S-48 (500ma) plate xfmr will handle all the current the xmtr will draw.  Remember the modulation current is not a steady load.  You could load the 813 to the full 170-180 ma (plate and screen current) at whatever plate voltage you end up with (probably about 1300VDC).  Your only limitation is the current running through the modulation xfmr secondary.  I think you are using the ART-13 mod xfmr.

I would fuse the primary at about 6-7amps.  Don't forget the higher in-rush AC current in the primary.

If the 120V AC relays are DPDT, you can bridge the two sets of contacts to control the xfmr primary.  You only need to relay the HOT side of the AC line.  The neutral can be left connected at all times.

In my previous post I mentioned putting the choke in the negative lead of the HV power supply.  There are some problems with doing this,  the choke is between the chassis ground and the center tap of the plate xfmr.  This raises the peak voltage on the CT to a high level, the xfmr may not be able to handle this.  I never use that method in any of my supplies.  I always put the choke (or chokes) in the positive lead.

You can put the Triad choke in the positive lead, at 1300 volts it should be OK, but I'm not a 100% on that.  You'll just have to try it and hope the choke doesn't short to ground.


You should always connect your equipment to the station ground.   You can use the ground rods BUT you should connect the station ground back to the building AC ground.  The AC panel ground and any other ground rods you add should be connected together with at least a #6 wire.  Also make sure that you have connected the HV PS chassis and the 813, 811 decks together.

Fred
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KB7HTV
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« Reply #92 on: May 10, 2011, 11:53:53 AM »

Yes,

Will have a neutral and a ground back to the panel from the transmitter power supply, I will also check all the ground rods and the wire size I used old copper stranded wire from an above ground overhead ac supply to the mast on my shack that I demo'd to put all electrical to the shack underground
I had a dedicated panel put in my shack which also has a couple of ground rods for it alone. as well as the ones that I put in separately to ground radios
the transmitter will have a dedicated 120V circuit just for the HV supply
the Filaments and 120V control will come from a separate circuit

I am building a 500V power supply for the Millen exciter and an optional small modulator for it, if I use it standalone, so same thing here have to sum up all the loads, I found a good old military transformer with a 570V. primary and several Filament windings, Have you seen the schematic for the Millen?
I found the original artical for the design in the 1943 ARRL handbook.
This will help with winding the coils for the thing, it is an old balanced output
link coil rig pretty neat but old school compared even with the 50's era designs meant to feed twinlead, no coax connector. so that is what I am working on as well as hunting up big resistors, chokes and the like for the 813 rig. the clamp tube is mounted in the chassis, boy do those greenlee chassis punches work slick

73 guys having too much fun
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