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Gen Rad automatic voltage regulator - for filament voltage stability




 
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Author Topic: Gen Rad automatic voltage regulator - for filament voltage stability  (Read 2421 times)
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KJ4OLL
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« on: September 26, 2015, 08:51:35 PM »

Hi,
I have read that it is important to keep the filament voltage accurate.
Noticed that my utility power is between 220 and 250, depending.

My Elmer told me years ago about a machine that would automatically regulate power to the linear.

Found an ancient, broken one on the auction place, fixed it up, and it actually works!




Capacitors had 1977 dates on them. One was obviously not too happy:




Three other capacitors were way off specs, but at least did not blow up.

The restored control board for the Gen Rad:



Internals:



It actually works!!!!!!

www.youtube.com/watch?v=m4stOtRMBpM
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W7TFO
WTF-OVER in 7 land Dennis
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IN A TRIODE NO ONE CAN HEAR YOU SCREEN


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« Reply #1 on: September 27, 2015, 12:45:28 AM »

Staco made a similar unit called the Stabiline.

Came in many sizes.

Your GR is a lot rarer and more complex.

Kudos!

73DG
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KJ4OLL
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« Reply #2 on: September 27, 2015, 09:40:55 AM »

Hi,

I'm trying to understand how to wire this to contemporary safety specifications.

The old schematic just shows how they did it back then, fuse box input and fuse box output.

I would like to wire it as a four-wire, L1, L2, Neutral, Ground.

L1, L2 wiring seems clear, (there is no jumper between 2,3 in the correction range option I selected)





The wire thay are calling "GROUND "WHITE" I think might actually be Neutral.

Neutral bypasses the Gen Rad "REGULATOR TERMINAL BOARD", and proceeds to the output panel.

If that seems OK, then not shown would be an earth ground, bonding the input panel, frame of the genrad, and output panel.




If that seems like the correct way to implement a 4 wire safety circuit for this contraption, I'll proceed.
73
Frank
KJ4OLL
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KA2DZT
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« Reply #3 on: September 27, 2015, 10:32:41 AM »

Last schematic looks like it's for 240 volt input  (red and black both hot)  White is the neutral and you can always add a ground wire to the frame.

Fred
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KO6YB
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« Reply #4 on: September 27, 2015, 05:15:03 PM »

Looks to be in very nice condition. I have one tucked away, perhaps a more standard model for 19" rack installation. You do not show the front panel in your photos, but from the back it does not look like a 19" rack mount (could be wrong). Mine will get put in use when I get my shop/shack area put together. Stan.
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KJ4OLL
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« Reply #5 on: September 27, 2015, 05:36:49 PM »

Yes, it is 240 input (or whatever), and 230 out.

I'm going to rack mount it, will have to move some other things to make space in one of the racks, at the bottom.

The Gen Rad has a cabinet and front handles, but the front panel also has rack mount slots, under the handles.
So I guess the handles are removed to rack mount it?



Trying to come up with a way/place to install a digital RMS AC volt meter, so I can set/monitor the output.
(Can't have too many knobs, dials, guages, switches, lights, indicators...)
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KJ4OLL
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« Reply #6 on: October 10, 2015, 09:07:53 AM »

Hi,

Because everything must be modified, put a modern AC volt meter in the ancient Gen Rad voltage regulator output.

Now to power up the connected amps and set the filament voltages!




73
Frank
KJ4OLL
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w4bfs
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« Reply #7 on: October 10, 2015, 11:29:42 AM »

having not seen the schematic diagram, I'm not sure what is going on ....

the output 230V relationship to the neutral is problematic unless you are comfortable with how it is established...

it needs to be sounded out because the 230V might be fine but the 115V to neutral may be hi/lo
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Patrick J. / KD5OEI
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« Reply #8 on: October 10, 2015, 02:00:30 PM »

I have the Staco type. I am glad as its circuit is simpler, however it has not ever failed. It is a little slower to act having a larger Adjust-A-Volt and stepper, but those things are OK with me as it keeps the voltage within 1-2V on 115V when adjusted right. I have a few comments, excuse me if I am only repeating what might have been discovered.

-Looks like it is mounted already.
-The handles look like they have holes that should be for the screwdriver to go through to install the rack screws.
-The ground is separate by today's standards, but you have to check that there is no connection in the unit between its neutral white wire and its chassis ground.
-It looks from the wiring chart that the buck boost transformer has dual windings for use with the connections you marked in red.
-Notice how the windings are split up differently from the single 115V hookup.
-The transformer hookup plus the dual variac on one shaft, tell me that it is not designed to adjust the two 115v lines independently but together as one.
-This is also indicated by it having only one buck boost transformer.
-Because of these factors I think there is no need to investigate further, just use it.



If the unit has a sensitivity control, setting it towards more sensitive may cause hunting at light loads but be more precise at high loads.
On the old Stabiline this is the case. For a given power rating, a better precision and greater freedom from hunting occurs under heavier loads.

Are these the right names?
General radio - Variac
Superior - Powerstat
Staco - Variac, Adjust-A-Volt
AE (India) - Dimmerstat

I like the lower case "v" on "variac" to generically call them rather than write out variable autotransformer.
Excuse me I have to grab a kleenex!
8-)
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