Power Transformer Identification and 230V to 120V

[Sven]

Hi,

I was hoping someone here would know a lot more about power transformers than I do since I haven't dealt with many of them.

I have a Heritage Kenny Burrell amp from 2004 that was made for Europe where I used it and I just recently brought it to the US. When looking at the power transformer I first thought I'm in luck because there is a set of unused wires (Blue) which I thought might be a second primary but now I'm not so sure anymore because there's resistance/continuity between the blue unused wires and the secondary windings.

I've identified the Primary (Black), 5V (Yellow), 6.3V (Green with CT), HV (Red with CT) and Bias (Blue with red stripe)

Has anyone seen a transformer like this and are the unused blue wires just another secondary?

If this is not a transformer that has multiple primaries for 120V/230V then I'll have to find a new transformer in which case I just wanted to know what measurements I need to get and ho to pick the right replacement transformer.

[shooter]

have you surfed up "schematic for....." yet, any luck?
a schematic is worth 1,000 guesses in the dark

[Sven]

Yes, there are no schematics for this amp unless I draw my own and I wasn't able to contact the amp designer either (Paul Cochrane)
Very little information on those amps.

Also the transformer is a ghost too, it has a label but I can't find anything about it either.

The label reads: PT-700-B   9960428

The output transformer has the same written label but also says "LIBERTY" so I'm guessing both are "LIBERTY" transformers.

[Sven]

I also just measured both unknown blue wires which are 642 VAC so it seems to be another secondary and not a primary. Seems like I have to find a new transformer?

Measurements are 728VAC on the Red Pair, 642VAC on the Blue Pair.

The Blue with red stripe which I called Bias before seems to be a tap of both Red and Blue? Measuring it within Blue equals 642VAC and Measuring it within Red equals 728VAC.
 

[sluckey]

Measurements are 728VAC on the Red Pair, 642VAC on the Blue Pair.

I think you have a dual voltage secondary, similar to this Hammond. Your blue wires would be like the red/whi wires on this Hammond...

     https://www.hammfg.com/files/parts/pdf/290D2X.pdf

Looks like you have no dual voltage primaries.

[Sven]

Oh interesting thank you! I imagine it would be a bit trickier to find the right transformer now but I'll try.

Another quick question id have about the amp:

I'm replacing the filter caps as they are 18 years old now. Nothing has failed and now is a good time to change them.

Should I just replace the big Filter caps or replace all electrolytic capacitors in one go while I'm in there? Do the small ones fail too? there's only 5 additional small ones and they're all low voltage 25V rated and two 100V.

Just wondering if it's common practice to replace everything.

[shooter]

I've found taking small bites causes less problems.  If it's a keeper amp buy them all, then go by sections PS filters, test, cathode caps, test...

[sluckey]

I would replace the transformer first. When you have it working with the new transformer, evaluate the amp. You may not need to do anything else.

I'm curious, how did you measure 728VAC on the Red Pair, 642VAC on the Blue Pair? I'm guessing you have a 120:240 step up transformer or plugged into a 240 outlet?

[Sven]

Thanks!

Yes I have a step up transformer which gives me 239VAC so it's a bit hot but close to what I'd get in europe. I'm just not sure if it's a good idea to run the amp on this step up transformer permanently? It say's it's 600W.

[Sven]

I would replace the transformer first. When you have it working with the new transformer, evaluate the amp. You may not need to do anything else.

Do you mean I shouldn't replace filter caps from 2004?

[PRR]

...I'm just not sure if it's a good idea to run the amp on this step up transformer permanently? It say's it's 600W.

600W amplifier? or 600W step-up?

Two 6L6 ought to be no-strain on a 600W step-up. (Remember the power supply network is transformers ALL the way down: 2kV on generator, 10kV in switchyard, 50kV cross-country, 20kV on my street, 250V on my feeder...)

[sluckey]

Do you mean I shouldn't replace filter caps from 2004?

I meant exactly what I said, nothing else. I said, "I would replace the transformer first. When you have it working with the new transformer, evaluate the amp. You may not need to do anything else."