Vibrato channel low volume in Bandmaster

[jim]

The normal channel is normal volume and clean.  The power amp is working fine.  Trading pre-amp tubes between channels shows the problem stays with the vibrato channel.  There is a hair of distortion whenvibrato volume is 10 but volume is real low.  Voltages on the tube socket look normal--235V on 1,6 and 1.6V on 3,8.  I replaced the bypass caps on the cathodes.  Funny thing is when I opened the chassis I founda 1/4 inch plug tip rolling around inside.   Also reverb and trem works OK on the vibrato channel--not modded for both channels.  How should I chase down the problem?  Thanks, Jim

[jordan86]

I have a 65 Showman and ran into this same issue when I got it a few years ago. I was informed here by more experienced guys that this is somewhat normal due to the load of the vibrato circuit on that channel. On my showman, I need to be at like 6-7 on the volume to match 4 on the normal channel.

[jim]

Actually trem does not work but I can see the roach flashing.   This volume is is super low barely audible. Jim

[pdf64]

Just to be clear, it’s a Bandmaster Reverb?
How about the V4 voltages? Including the grids.

[jim]

OK voltages are 231V 1,6;  0V on grids;  1.8V on cathodes.   But when I simply touched pin 6 with the test lead there was the usual static and then the channel suddenly came alive.  What did I do--should I remelt the solder and call it a day?  I dont't understand.  But I appreciate your insight.  Jim

[jim]

Likely corrosion and fifty years of grime on the tube socket.  Ill clean it up.  Thanks!

[uki]

remelt the solder and ...

Do that not only for that part of the amp , but do a check on everything, is the amp old?