Fender 5150 III low output

[drewl]

Pretty new 50w head only putting out a couple watts.

Somewhere the signal is getting lost between the preamp and phase inverter.
Also phase inverter voltages seem odd, like 100vdc on all the pins except filaments.

Not sure which tube does what but I have a large signal on the farthest preamp tubes that doesn't make it to the FX send.
Injecting signal into FX return gets alot more output.
Looks like loop is SS, I think one of the opamps is bad, unless half is not used.

Haven't dug too far in, but any schems for these around?
Quite a different layout than the Peavey versions.

[Enzo]

Guitar Amplifier Schematics and more

Go there, scroll down to fender, and it is the third one down.

[drewl]

Thank you.
I actually have that site bookmarked.

This amp was modded by a well known company so ch1 & 2 have separate dual gain and volume pots.

The problem was the phase inverter with those bad voltage readings.

The 100k resistor on the pi pin 7 was replaced with a jumper that wasn't making a good connection.

Don't know if it was modded or came from the factory that way but it doesn't look like it.

All versions of the amp have that 100k in there.