Hickok 6000A Power Teansformer

W9TR

W9TR

Super Member
I have managed to open one of the HV windings in my Hickok 6000A tester. The one that feeds the plates of the 5Y3. Screen voltage is now 70 Vdc and the neon short lights don’t light.

Any advice on securing a working transformer?
 
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gadget73 said:
If its only one open winding, honestly I'd be real tempted to add in one extra transformer to handle that part only. Short of a good original or paying for a re-wind or a custom job I don't see a viable way to replace it. Its got too many windings and too many taps.

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Thanks for the quick reply. Great minds think alike. Only one winding is open, terminal ‘O’ so I was thinking I could add a 320V CT transformer. That’s not a sure thing since the primary is in series with a variable reisistor but I can probably work around that.

Finding a 320 VCT transformer may be difficult and so far I’ve come up blank.

A donor unit may be my best bet - my tester is in above average cosmetic shape so I’d like to try and keep it going.
 
gadget73 said:
If its only one open winding, honestly I'd be real tempted to add in one extra transformer to handle that part only. Short of a good original or paying for a re-wind or a custom job I don't see a viable way to replace it. Its got too many windings and too many taps.

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Have you ever had one of these monsters re-wound? How well did that work out?

Thanks!
 
I've never had a transformer re-wound. Its just definitely not going to be an off the shelf part. A custom wind or a re-wind should be functionally the same, and the only way I can think of you get such a goofy combo of voltages.
 
W9TR said:
Yep, that price was not unexpected given the complexity of the job. So I’ll be looking for a donor unit. Maybe someone has one with a bad meter and a good transformer.
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I'm glad my testers are still testing healthy. If one were to blow a transformer, $850 would be a hard bullet to bite.

Chris Haedt did such a great job restoring the Hickoks. I wish he were still around. :(
 
Antek has a toroid with dual 175V windings (181V unloaded @ 120V). Might be about right if the primary is connected after the line adjust rheostat. That should be OK, as it only draws 16 mA unloaded, under load would be that much more than the existing transformer. But it would add another 4 pounds and it's $42 plus shipping... it's a 100VA transformer. Actually I recall having something in that voltage range, but it might be even bigger. I'll look, will PM.

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Mr Boochie said:
I'm glad my testers are still testing healthy. If one were to blow a transformer, $850 would be a hard bullet to bite.
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My Eico simply wouldn't be worth spending that much on, so it would just get replaced with a different tester.

though it would be a good excuse to buy myself a curve tracer and stuff into that box, provided the wiring wouldn't glitch out the tracer. The Eico 667 has switching capability that lets me assign any pin to any function, so if you know the base arrangement its just a matter of setting the levers to the right spot.
 
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Tom Bavis said:
Antek has a toroid with dual 175V windings (181V unloaded @ 120V). Might be about right if the primary is connected after the line adjust rheostat. That should be OK, as it only draws 16 mA unloaded, under load would be that much more than the existing transformer. But it would add another 4 pounds and it's $42 plus shipping... it's a 100VA transformer. Actually I recall having something in that voltage range, but it might be even bigger. I'll look, will PM.

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Thanks Tom got your message!
 
gadget73 said:
My Eico simply wouldn't be worth spending that much on, so it would just get replaced with a different tester.

though it would be a good excuse to buy myself a curve tracer and stuff into that box, provided the wiring wouldn't glitch out the tracer. The Eico 667 has switching capability that lets me assign any pin to any function, so if you know the base arrangement it’s just a matter of setting the levers to the right spot.
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In this case although I think the rewind price is fair the juice isn’t worth the squeeze. I’ll add a new HV xfmr or wait to find a suitable donor. I thought about one of the curve tracer kits and the switching ability of this tester would make one universal and save a lot of work. But my tester is in nice shape so I want to try and fix it. IMG_3925.jpeg
 
Looks like equivalent switching, just done in the opposite manner. You get one control per function and assign it to a pin. I get one switch per pin and assign it to a function.
 
I also have a Hickok with an open transformer winding. It's either a 6000 or 6000A, been sitting out in my storage shed for more than 10 years now. I don't think there's a practical way to salvage this situation unless you're willing to make a Franken-tester.

Jack
 
A quick update. I purchased a 320V CT transformer from Tom Bavis and he sent it the same day. Much appreciated Tom. I couldn’t be happier. This is the way things should work.

I wired in the transformer and it works - I am able to test KT-88’s and the tester tagged a bad tube that was cause of some issues with my MC 275.

The secondary voltage is about 25% low due to the resistance of the line adjustment pot lowering the primary voltage to about 98 Vac.

What it tells me is that this technique will work! I just need to take some time to find a suitable transformer and again, Tom to the rescue with a link to Antec, which has a wide variety of toroidal transformers with different secondary voltages. I have some math and measurements to do to get to 135V on the screen supply and get also the correct bias voltages, which are derived from the screen supply.

That’s a task for tomorrow.

IMG_3995.jpeg
 
I don't suppose the transformer Tom sent has a 6v winding that isn't being used? If so you could re-configure that as a boost winding to effectively add 5% over whatever comes out of the line adjust pot. May or may not be enough.

Failing that most of the Antek ones do have a 6v winding or two which could be used for the same purpose.
 
Yep, I phased the 6 V winding to maximize the secondary voltage.

The main transformer primary is 94.2 Vrms when the meter reads ‘Line’ and the transconductance signal reads 2.50 Vrms.

At the same time the now unloaded good secondary reads 166V rms @ 94.2 Vrms on the xfmr primary. That’s a ratio of 1.76.

So for a nominal 120Vrms transformer I’ll need 211 V unloaded at the secondary.

I’m on the hunt. The Antek transformers have multiple 6.3 V windongs, some center tapped, so I’m sure I’ll find something that will work.
 
I ordered an Antek AS-05TC200. Two 200V secondaries, two 6.3 V windings, OC Vrms is 207 Vrms so very close to what I need. I can tweak with the 6 V and 5V windings as needed under load.

The nice 320Vct transformer I got from Tom will end up in a project at some time. Maybe a headphone amp?
 
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