Studer A80 recap maybe Lundahl Transformer ?

Hi Greg,
Yes, I was referring only to the precision caps used on the equalization circuits, not the tantalum/electro types.
Sorry for the possible confusion, the term " recapping " is large...and from my experience some people who embark on "recapping " don't really know what they are doing...looks to me that "recapping " has turned quite " fashionnable " now in the studio world.... ??? 

Back to your A80 " spitting and popping"  ;D
This phenomenom is the typical sign of one/several A101 opamp diyng soon...
The 9 pin A101 opamp used 4 transistors, 5 resistors and one cap.
They were Studer designed and made, and for three generations.
First generation was a black can, terrible, along the time they were ALL diyng.
I would be surprised that it would remain some alive now...
They were replaced by the blue can, that was better but still many of them turned bad along the years...
Third generation was very reliable, using standard discrete componants and...not potted...may be the secret of their reliability ?
I have changed hundreds of A101 opamps of first and second generation in the 70's and 80's.

In the studio complex where I was at this time we needed so many A101's that we decided to build them ourselves ! ( DIY ha! ha ! )
Each finished A101 costed 1/12th of the price that Studer was charging as spares...  ;D

I still have a few blank A101 pcb's around my mess...
Guy

Thanks for the info. The "Record Driver Amp" has one A101 (non-potted) and a bias driver. It appears that some models have two A101s. This is interesting. Do you have any insight on what exactly causes the popping. Perhaps failing transistor junctions?.

 

Hi Greg,
No, I have no idea of the cause of the A101's failing.
Studer probably has the answer, but it is such an old story that nobody in Redensdorf remembers what a A101 was
Just remove the culprit(s), solder a new unpotted " third generation" A101 and you're back in business 
Guy