Mk III troubleshooting

[jpo]

Hello all,
newbie question... I have a Mk III blue stripe simul-class head which went dead silent while playing. I switched off the standby and then on again and it worked for a minute and died again for good.
I get sound when I plug my guitar to effects return. So preamp tube it is?
Bought a new set of 12ax7's. Still nothing.
V1 tube doesn't "glow" at all like the others do and it doesn't warm up. I tried 3 different tubes in that position. No effect.
I assume that it is not a tube problem then.
Switching between channels won't help either.
Any ideas before I take this to a repair?
Amp was in a repair shop few weeks ago. It was cleaned and one capasitor and all power tubes were replaced.
Also I have amp out of headshell right now while testing and I have the reverb cables disconnected. Would that affect anything ( except no reverb...) ?
Thanks for any input.

 

[daveg62]

amp will still work without reverb plugged in. does sound like the preamp section if you get sound going into the fx return. If amp is out of headshell I would look real close at tube socket wiring and solder joints. I'm sure someone else will chime in soon with ideas. good luck!

 

[Mister Joshua]

I concur with Dave. It sounds like something in or around the tube socket died. Unless you are a master solderer and master troubleshooter it would be advisable to take it to a tech.

Peace,
Joshua

 

[stokes]

If there is no glow in the filament in V1,that is the problem,check pin 4&5,should be tied together and have a green wire soldered to it,and pin 9,should also have a green wire soldered to it.When looking at the bootom of the socket,or from inside the chassis,you will see a wider space between 2 of the pins,the one to the left of this space is pin 1 and to the right,pin 9

 

[jpo]

Thanks guys,
amp is going to a tech. I'll let you know the cause when I get it back.