Restoring my old ST-70 and the power xfmr primary has resistance of only 2.3 ohms. Still seems to work if I ramp up the primary voltage with a variac but gets warm quickly and is not happy with 120v across the primaries... must be breakdown in the insulation on the windings. Anyway, looking for a new or good working used transformer. If anyone has one they'd sell or know a source that has stock. please reply.
3 posters
Wanted: PA 521 or PA 060 transformer
Kevin- Posts : 2
Join date : 2021-04-28
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
Kevin wrote:Restoring my old ST-70 and the power xfmr primary has resistance of only 2.3 ohms. Still seems to work if I ramp up the primary voltage with a variac but gets warm quickly and is not happy with 120v across the primaries... must be breakdown in the insulation on the windings. Anyway, looking for a new or good working used transformer. If anyone has one they'd sell or know a source that has stock. please reply.
See https://www.dynakitparts.com/shop/pa521-power-xfmr/
PA521 is avaiable but PA060 is currently out of stock
Kevin- Posts : 2
Join date : 2021-04-28
Hi. I did see that. 2 follow ups... they claim that this is a pa521 but then say it's 240V only... I know the original Pa521 has dual primaries... meaning in parallel they can be used for 120v and in series for 240v... so was not clear this would work for me because I am a 120v power person ;-) 2nd... any idea why all the pa 60 supplies seem to be out of stock? I supposed a 3rd... has anyone tried to "rewind" a Pa60 that isn't working as it should?
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
Another source within US is http://triodeelectronics.com/mq060.htmlKevin wrote:Hi. I did see that. 2 follow ups... they claim that this is a pa521 but then say it's 240V only... I know the original Pa521 has dual primaries... meaning in parallel they can be used for 120v and in series for 240v... so was not clear this would work for me because I am a 120v power person ;-) 2nd... any idea why all the pa 60 supplies seem to be out of stock? I supposed a 3rd... has anyone tried to "rewind" a Pa60 that isn't working as it should?
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
You are correct about the pa521 from dynakitparts.com.Kevin wrote:Hi. I did see that. 2 follow ups... they claim that this is a pa521 but then say it's 240V only... I know the original Pa521 has dual primaries... meaning in parallel they can be used for 120v and in series for 240v... so was not clear this would work for me because I am a 120v power person ;-) 2nd... any idea why all the pa 60 supplies seem to be out of stock? I supposed a 3rd... has anyone tried to "rewind" a Pa60 that isn't working as it should?
A bird whispered in my ear that dynakitparts have PA060 within a week or so, take the
opportunity to order one.
Tom Pickett- Posts : 203
Join date : 2020-11-22
Age : 58
Location : Texas
Kevin wrote:Restoring my old ST-70 and the power xfmr primary has resistance of only 2.3 ohms. Still seems to work if I ramp up the primary voltage with a variac but gets warm quickly and is not happy with 120v across the primaries... must be breakdown in the insulation on the windings. Anyway, looking for a new or good working used transformer. If anyone has one they'd sell or know a source that has stock. please reply.
As peterh pointed out Triode and Dynakit.... also the two transformers from Triode and Dynakit are virtually identical but on the other hand Dynakit offers theirs $30 cheaper than Triode.
Another good point about the new PA060 is that it's much more robust than the original Dynaco PA060. The lamination stack is much taller and the transformer will run much cooler than the original.
I'm not certain about this but it may even be the same PA060 transformer that Bob offers in his VTA ST 70 kits ?