Peavey 5150 has lost it's Gain... Help

[CoopDaKill]

I've had my Peavey 5150 head for many years. Original owner. Lately, it just dont have the pre-gain that it used to. Been having to turn up the gain to about 7, when normally I would run it at about 3 - 4. The amp has plenty of volume. I've tried different tubes that I have laying around, but no change. The amps' tone seems to have gotten thin and weak. Any advise would be welcomed. Coop.

[Amp Kat]

Make sure all of the preamp tubes are lighting then take a known good 12AX7 and go down the line one by one and change them out with the known good one.

[Jazz P Bass]

Peavey 5050

I would try replacing the output tubes.

[j. Bacj]

Gain problems

Hi I have the same problem to, and it`s not the output tubes. I am very happy with my peavey 5150, so it would be a shame to get rid of it...
all of the tubes are changed and the same problems go on??

[Amp Kat]

Try taking a guitar cable and patch it from the send to return and see if it comes back.