Do you mean that I have to put a voltage on the secondary side e.g. and see what is measured on the primary side? The ac voltage there should meet then the anode voltage when the amp is in max. use?
I understand the concept, but it would fail to notice a fault on one side. You could have a shorted side and still get a valid output. And unless you very carefully compared it to a known good transformer, you really know nothing. Doing it in reverse you can compare each half of the primary. And let's face it, if something failed, it's most likely the primary winding in some way. It makes much more sense to do it in reverse.
Also, hooking mains directly to a possibly damaged transformer sounds like a bad idea to me too.
Yes, remember it's stepping up... so 3v AC might become 60 or 120V etc.. depending on the exact ratio of the unit. The thing I like is you can compare from the center tap each half of the transformer and make sure the voltage on each side matches. It's possible for one side to short, think 40 turns is now 20, and in that case would see very different AC values on each half. They don't have to be perfect (and likely won't be) but if they are significantly off, it's likely bad. Or you could even have 1 side not working at all if it opened.
Actually that's not quite right, due to mutual inductance a short in one side of the primary will affect the results across the entire primary. An open likewise would do the same (that's somewhat more obvious). Testing across the primary is a time honored way to determine whether there are shorts in either primary or secondary (again mutual inductance) and to measure primary current at a known frequency and voltage and determine the inductance under conditions that more closely approach normal operating conditions. Use an isolation transformer for safety. Some means of limiting current in the primary is recommended, and I strongly recommend checking the transformer for winding to core shorts first.
How you can do a power transformer with shorted turns to run "valid " ? This is the same , doesn't matter if it is an output transformer . In coupled windings any shorted turn would make the whole transformer to be bad . And both halves of a push-pull transformer are in phase , just to be clear , from plate to plate it is not canceling out . Remenber that a 220V power transformer with 110V tap can be used as a push-pull transformer very well .
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I did some tests (very carefully) With the result 12V on the 4 ohm output, gave me 2 x 163V (a-mid) (315V a-a) on the primary coil. Both transformers gave the same result. I think there is nothing wrong with my output transformers. I will now repear the rest of the amp and test the tubes if I can still use them .
This basically is what I recommended in #16, and it allows to disclose shorts in one primary half as well by comparing the voltage readings from CT to each plate terminal.
In a defunct power transformer of an old Dynacord Eminent II amplifier I found exactly which winding is partially shorted by this way. It's one of both plate supply secondaries.
Best regards!
This is good news. I would probably replace all of those output tubes. The Russian 6P14P-EV is rugged enough for operation at these elevated voltages. Try to get matched quads if possible. Best sources are probably eBay sellers in former Soviet bloc countries.
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Anode voltage 440V ??? This amp Getling throws its barrels as a weapon ... The EL 84 can dissipate 12W and the Russian 14W. Guitar amps are used to be stretched like this, if someone did something like that with an animal, I would be imprisoned for life ... 🙂
It can be done close to class B , the power dissipation / current is high only when you are listening at very high volume .
yes, if the dc resistances are not the same, but even them there will be difference...