[ronaldw441]

Two questions;

1) What are the specifications for the output transformers in a Jolida SJ-502A? I believe the part number is SG-50A.

2) Should I replace my bad transformer with another Jolida or replace both with Edcors or Hammonds?

Information and/or opinions appreciated.

Thanks

[Bill Baker]

A suitable replacement for the Jolida transformers is the Hammond 1650P 60watt/6,600 CT.
Parts Express part # 122-145

[ronaldw441]

Thank you for the reply.

Your reply brings up another question.

Is there an advantage to using 6,600 ohm transformers?

I did a little research & used the following method to measure the other good Jolida transformer. Output of variac & isolation transformer to plate leads. Increase voltage until 8 ohm output is 1 volt. Divide input voltage by output voltage to determine turns ratio. Square ratio then multiply by 8 to determine approximate primary impedance.

Using this method the Jolida transformer appears to be about 4,100 ohms.

A pair of Hammond 1650P's that I picked up today measured 6,650 ohms so it would seem that this test method works fairly well.

Thanks again

Ron

[phi70]

Trying to revive this age old thread.
Does anyone have an orphaned  power and output transformer they want to part with.
Some evil person decided to put a 15A fuse into my 502, break off the guide pins of my power tubes, and caused a major meltdown destroying the power tranny and one output tranny.
Just trying my luck here before hoing for Hammond 291ZZ and 1650NA (or is it 1650PA)?
Thank you all in advance

[audiobasic2000]

Good Afternoon, phi70:

Have you tried contacting Michael Allen at Jolida, now Black Ice to see if they may have a replacement transformer?   

Contact page - https://www.jolida.com/contactus ... e-mail - info@jolida.com (or possibly JOLIDACORP@MSN.COM)   

Thanks.

Sincerely,
Kingsley.

[JackD]

Also Bill Baker with Response Audio

[billc]

Bill might have some inventory, but you should contact Jolida.  Their entre to the audio world was as a designer of transformers.
The following text is from the Jolida About Us web page: “ In 1991, JoLida designed a series of large transformers for an industrial customer in which one of the main design criteria was low noise over a wide signal bandwidth. It was then suggested that if the size of the transformers were reduced, they would be highly applicable to tube amplifiers. Please note that in a tube amplifier, the transformer is the heart of the unit. ‘. The 502 was one of the products of this initiative….  Used to have a 502 modified by Bill.  A friend has it now and loves it

Bill C

[phi70]

Thanks all.  My unit that got fried was one of Bill B's creation too.  Earlier model. Served me well over many years until it was mercilessly smoked by someone who borrowed the amp.