Univox U-1075 PA amp

[Axtman]

I have an old Univox U-1075 PA amp that I am repairing. The problem is very low output. It has 4 6L6 tubes so it should be really loud.

I check all the tubes and plate voltages and they seem to be fine. I am puzzled on why such a low output.

Any advice would be appreciated. Thanks.

Oh here is a possible clue. The preamp and phase inverter tubes don't get hot, they only get warm.

[Jazz P Bass]

Measure the Vac signal at any 6L6 grid with all controls full on.

If you are using a signal generator set it for a 100mv output at 1K frequency.

If not, use a guitar with the volume full on & bang away at a power chord.

You should see a good healthy 100 Vac (approx) at the grids.