Roadster Head ch 3 and 4 no volume

[crazy4k9]

Last weekend I had a gig. Everything sounded great in soundcheck. Right before we started, I turned on ch 3 and there was almost no volume. Ch 4 was the same. Clean ch 1 and ch 2 were fine. I had to crank the volume on 3 and 4 almost all the way up to get enough sound. Tonight, I swapped out every preamp tube one at a time and nothing improved. I have had numerous problems with my head in the 7 months I have had it. Very disappointing for a $2k amp. Can anyone help me out?? The closest authorized repair shop is almost 90 minutes away. Thanks.

 

[Supreeth]

I had this exact problem with my Roadster when I changed tubes a while ago. I found that preamp tube v3 was the culprit. The strange thing was that the tube had not lost vacuum and looked just fine (no white Barium Oxide to indicate that the tube had lost vacuum). I put a new tube in the v3 slot and I was back in business. Your issue definitely seems like the problem I had but the fact that you've already swapped out the tubes with no good results seems to suggest otherwise.I think it would be worth a try to put in a new tube in v3 even though you mentioned you've already swapped out the tubes. If v3 is fine, also try v4 and v5. v6 is the phase inverter and since the clean channels are fine I would think that v6 is good. Keep us posted on how things go.

EDIT: I would also suggest cleaning the tube slots with some contact cleaner. It might just be that some slots may be a little dirty.

Thanks,
Supreeth

 

[LithiumZero]

I had the same problem with my Roadster combo. It was a bad tube in V3. Changed it and haven't had a problem since.

 

[crazy4k9]

I must have been going to quick when I checked each tube before. Pulled V3, put in a new tube, and sure enough I am back in business. Thanks!!! My only concern is my amp seems to be going through preamp tubes. The guy at the shop said occationally Mesa will have a bad batch of tubes. Hopefully this is fixed for a while.