Fender Twin loud reverb hiss

[deathofaparty]

I've noticed that in the last year or two my 65 Twin Reverb Reissue has developed a loud hiss that is in direct relation to the level the reverb is set on. It's almost like the reverb control is a hiss control. It's more prominent than the standard reverb hiss. Anyone have any tips on what to do?

I'm a noob to amps, but have built a good amount of diy pedals and electronics.

Thanks.

[Jazz P Bass]

Reverb hiss

I just finished a 65 Twin reissue repair.
Same thing. Above 5 the hiss was terrible.
I checked "everything". Never found it.
I ended up putting a 12AT7 in the reverb recovery.(V4)
Some would call it a mixer.
I also put a 12AU7 in the phase inverter.

[deathofaparty]

And that worked? Any chance you can tell me where those are?

[acorkos]

try replacing v3 and v4 first with the correct tubes before doing any type-swapping. check out the section on hiss here...

Tube Amplifier Debugging Page

[Jazz P Bass]

Reverb Hiss

And that worked? Any chance you can tell me where those are?

It did not "fix" the hiss.
Just made it less objectionable.
V6, phase inverter, is the last 12AX7 before the 6L6 output tubes.
The tubes are numbered in order. 1-6.
Attached is the schematic.