need help with Roadster combo, cutting out after 2 hrs

[urban41]

I bought a Roadster combo used, and it plays great, but after about 2 hrs of hard practicing with the band it simply quits. If I let it sit unplugged for 20 minutes or so it is back to 100% again, but will then quit after another couple hours. Is it an overheating problem? Our practice space is cramped and hot, and a fan set up behind it did seem to help. Or is it a sign that a tube or tubes is/are going bad? Otherwise, there are no issues with the sound, no buzzing, noise, etc and the fuse is fine. Any help would be much appreciated. thanks

 

[BostonRedSox]

Check preamp tube slots V3 and V5. Weak tubes or Russian tubes in these slots can cause the problems you are describing. I would swap out either slot with a chinese tube or a Mesa branded tube, which is a JJs tube if you are interested. Mesa switched to rebranding JJs because they are more solid in these fickle preamp tube positions. Try one tube slot first, play, and see if your problem is solved. If it isn't, return the old tube back to the slot and then move on to the other slot. You should find your solution in no time.

 

[domct203]

Read Here for more info on the cathode follower preamp tube positions.

Dom

 

[urban41]

thanks for the quick replies -- those are both very helpful