Blues Junior trouble

[Rocknrollampsinc]

I have a cream board 2003 Rev A blues junior on the bench with a bad howling feedback coming out of the reverb. The reverb is also noisy and hissy but it works. The Fender drawing number is 0057275000. Tried moving wires around and rebending the ribbon cables. Continuity through reverb cables.

Any thoughts would be appreciated

Jack

page number 2

http://support.fender.com/schematics/guitar_amplifiers/Blues_Junior_Schematic.pdf

[phsyconoodler]

Check the cables again.The shielding is what you need to check.If the shielding isn't grounded it will squeal and hiss.They ground to a point on the PC board and they must contact the reverb tank.One or both sides,not sure on that amp.

[Rocknrollampsinc]

thanks for your reply
Both shields show ground
Also tested pan to ground through each shield individually.

[Jerry Glass]

The send shield should NOT be at ground potential; if it is, it will send the gain of the op amp through the roof by killing the inverting signal at pin 6.

[Rocknrollampsinc]

The send shield should NOT be at ground potential; if it is, it will send the gain of the op amp through the roof by killing the inverting signal at pin 6.

Thanks for that reply. While I am not as knowledgeable in solid state as you seem to be, in my frenzy to figure out what was wrong (customer was sitting right behind me, waiting) the fact that pin 6 is held off ground by R39 just blew right by me. Glad you noticed. I will check that out!
Again thanks for taking the time to reply.
Jack

[Rocknrollampsinc]

Shield of send is functioning properly, there is no short.
Any other ideas?
Jack