Problem with my PV10B

[Sushimaster]

I have a PV10B line only preamp and it was working fine.
Trouble started when I decided to roll some tubes.
I bought some NOS Tungsram 12au7 and plugged them in and one channel (Right) developed no sound while producing a noticeable hum.
My first thought was a defective new tube, so I put back my original JAN Philips ECG 5814A tubes, but still the same issue...no music, and a pronounced hum. I swapped left and right tubes, same problem, so I know it's not the tubes.

My thoughts are:
1. Bad tube socket/cold solder joint (I reflowed the solder under both 9 pin sockets but the problem is still there)
2. Dirty tube pins (but I tried cleaning it with Deoxit, reseating the tube, and the problem still persists)
3. Maybe the new tubes draws too much current and damaged a capacitor/resistor?

Your thoughts appreciated.

[admin]

First, welcome to CJO. Great to have you with us.

Sorry you are having an issue with your PV10B. It must be doubly frustrating that you were hoping to get better sound out of new tubes only to have disaster strike.

It sounds like you did a pretty good job with making sure the tube socket is not the culprit. The fact that when putting back the original tube didn't solve the problem, it makes me think there was some damage down the line. I would be very cautious with using the NOS Tungsram anywhere else prior to it being tested. You don't want any more damage being done in case this was the original cause.

I presume you looked at all the components inside for signs of malfunction (ie burn marks, bulging caps, etc)? I'm not familiar with the PV10B design but if you can isolate the L and R channels, you may be able to compare some of the components in the signal path with a multi-meter and perhaps get lucky in identify a fault?

[Sushimaster]

Thanks, it's a pleasure to be here.
I didn't see any obvious damage, but I'm suspicious as well to there being some.
I'll try testing with multimeter/perhaps replacing some components.
Worst case I suppose will be sending it off to Conrad Johnson for repairs.
Thanks.

[admin]

We do have the PV10 schematics in our database so that may help identifying a signal path specifically to look at.