5150 low output issue

[Redline]

I have a 5150 sig head that has very low output volume. I tried the fx loop cleaning and patch cable. Still has low output. The eq and gain controls are not responding. Both channels have the same issue.

[tedmich]

always check tubes especially the PI (V4 closest to power tubes, I believe) but another common issue is one of the JFETs used to mute during channel switching, Q7 gives this low output when it goes, removing it should louden things up, replacements are a couple bucks. You have to pull main board and desolder to fix if its Q7.

[tedmich]

there was an odd report of a non-functional master volume in a 5150 that was traced to a bad 22uF PS cap (C27 last preamp PS node)