Welborne Terraplane Amp-PS10 HV Regulated PS Problems

[Raj1]

Gosh man, I'm stumped cos those all measure fine. Can't think of what else it could be.

 

[Raj1]

Ok I had another look today and something is causing R1 to glow red freaking hot in one of the amps (that's without any tubes inserted)..

 

[ThorstenL]

Hi,

Ok I had another look today and something is causing R1 to glow red freaking hot in one of the amps (that's without any tubes inserted)..

Is that R1 on the PS10 PCB (the one that can be replaced by a choke?), if so it suggests a major short somewhere.

Given that PS10 circuit is known and documented and not difficult, maybe you find a local electronics repairer that can handle tube stuff and let him fix it?

Ciao T

 

[Raj1]

Hi Throsten,

Yes it is R1 from the schematic (the choke substitute), I think what I might do is order in every single part and do a complete replacement on both PSUs and see what happens. Right now I can't find where it's shorting with the DMM, I guess I'm missing something, though.

Thanks for your help by the way, it is very much appreciated. And Happy New Year!

-Raja

 

[6L6]

Raj1 - just to clarify, you have R1 in the circuit in lieu of the choke, correct? Not both?

You said it's an older version regulator - a PS-3 perhaps? Is it a single sided PCB of raw fiberglass? Or does it have the big film caps and the 2 boards like the one photographed?
I have a PS-3 somewhere, I could post a photo to help identify.

What is the regulator connected to? Main B+? A filament? The driver tubes?

Also, I would correspond with Jack Elliano of Electra-Print if you think you have a problem with one of his transformers. He is very responsive on email. You didn't mention what amp you have, and if it's a Welborne, Jack didn't make the power transformer, as dsavtisk said. He could make a replacement, however... (and a big choke for the psu) ((which very rarely have problems, unlike regulators...))

Anyway, can you post some photos and a schematic of exactily what you have? Hand drawn is just fine around here...

Cheers! And a happy 2011 to you and yours!

 

[Raj1]

Raj1 - just to clarify, you have R1 in the circuit in lieu of the choke, correct? Not both?

Hi 6L6, it's just R1 I think the actual value is somewhere around 50 ohms. The amp in which the resistor glows red hot is now measuring around 2k on the same resistor.

You said it's an older version regulator - a PS-3 perhaps? Is it a single sided PCB of raw fiberglass? Or does it have the big film caps and the 2 boards like the one photographed?
I have a PS-3 somewhere, I could post a photo to help identify.

What is the regulator connected to? Main B+? A filament? The driver tubes?

It is a dual PCB design, quite similar to the PS-10 but a bit bigger, I think the driver tube section is added on to the version I have. These amps were the only two made by Welborne and were replaced in the Welborne lineup by the DRD designs afterwards. Anyway, it's a choke loaded 6N1P~300B (Sophia Electric Princess 2.5V filament).

Also, I would correspond with Jack Elliano of Electra-Print if you think you have a problem with one of his transformers. He is very responsive on email. You didn't mention what amp you have, and if it's a Welborne, Jack didn't make the power transformer, as dsavtisk said. He could make a replacement, however... (and a big choke for the psu) ((which very rarely have problems, unlike regulators...))

I don't think the trannies have a problem now to be honest, something in the regulators has gone brutally short - either that or the initial FET blow slapped R1 so hard that it needs replacing.

Anyway, can you post some photos and a schematic of exactily what you have? Hand drawn is just fine around here...

I'll have a bash at drawing it out, not really my forte but I think I should be able to manage something close enough for you guys to grasp what is what.

Cheers! And a happy 2011 to you and yours!

Thank you! Same to you, hope you have a prosperous 2011!


-Raja

 

[6L6]

Bigger than a PS-10? It's huge! Perhaps a prototype...

Did you buy these as a kit or factory-wired?

Anyway, you should really think about adding a choke instead or R1. That would probably help keep everything happy once the regulator is fixed.

 

[Raj1]

Hi,

I'll try and post a pic in a bit so you can see how long these are. They were "factory built", i think Ron used these amps at shows for a while.

-Raja

 

[Raj1]

Here it is...

An externally hosted image should be here but it was not working when we last tested it.

 

[6L6]

Looks like a PS-10 with an additional circuit.

Do those amps have an aged-metal looking cover over the transformers? Are they parallel-feed? (In other words, are these the Moondogs?)

Copper and Wenge - pretty!!

What are the voltages on the blue electrolytics? I.E., are they filament or B+?

I would strongly suggest heatsinks on the TO-220 diodes. They get hot, and then fail. A small fan to move some air around the regulator would also be a very good idea.

 

[Raj1]

Hi 6L6,

I don't think they are parafeed, although yes when i got them the copper had a patina. The blue electrolytes are filament (10V 10,000uf). I'll get some small heatsinks to put on the rectifier diodes for sure.

Think I'm gonna have to replace all the PSU components in one swoop and see what gives..

-Raja