Drawmer 1960 Gain Reduction Issue

[brendandwyer]

So my Drawmer 1960 is exhibiting no gain reduction on channel 2.  I've checked any board to board connectors and it appears the crimp connectors are soldered to the board and not removable so i rule out loose connections. 

Anyone have a suggestion on where to start?

 

[scott2000]

If you have 2 channels, should be easy enough to take some readings and compare...... ..

Maybe a bad cap somewhere....

Link to schematic

https://groupdiy.com/index.php?topic=44990.0 ....

 

[brendandwyer]

Thank you

 

[gyraf]

Can be hard to fix if you have the potted version they did early on, probably to hide the fact that it was a FET-compressor, not a -tube.  Attached inside description, not verified in detail though.

Someone mentioned that the FET was a 2N4091

if you suspect it's a capacitor gone bad, then look at the 220uF, here designated C14

Jakob E.

 

[emrr]

I tried to work on an early one for a customer, and discovered there are two different gain cell pin-outs, with the earliest not being a part they recognized at the time.  Suggestion from Drawmer was to send it in.  This was probably 15 years ago. 

 

[brendandwyer]

Can be hard to fix if you have the potted version they did early on, probably to hide the fact that it was a FET-compressor, not a -tube.  Attached inside description, not verified in detail though.

Someone mentioned that the FET was a 2N4091

if you suspect it's a capacitor gone bad, then look at the 220uF, here designated C14

Jakob E.

Excellent!  Thanks

 

[danparaschivescu2016]

Can be hard to fix if you have the potted version they did early on, probably to hide the fact that it was a FET-compressor, not a -tube.  Attached inside description, not verified in detail though.

Someone mentioned that the FET was a 2N4091

if you suspect it's a capacitor gone bad, then look at the 220uF, here designated C14

Jakob E.

Thanks for schematic!
I could have sworn it a varimu! Some minimal...