| Author | Message | ||
| Brian Beebe |
I bought a 112 Sixty-Five made in 1979 which had no reverb. My amp tech put in a new Acutronics long reverb tank and a newer op-amp. Now the amp just sounds bad. It has no clean headroom and starts breaking up above 3 on volume and sounds harsh. I put the old op-amp back in but there's no change. The reverb saturates when turned up to 1 and the tremolo runs at full intensity at about 4 and starts to double back on itself above that. I'm hoping all these problems are symptomatic of one simple fix. Any ideas please? Thanks, Brian | ||
| mike kaus |
Did it start when he put in the reverb? It shouldn't have but possible. Try unplugging the tank completely from under the chassis and see what it does. Then let us know. It sounds also like maybe he biased it while it was there and played the "it's just like a fender" game and biased it around 35mA per tube and it's cooking. | ||
| Steve Kennedy (admin) Username: admin Registered: 03-2002 |
I agree... obviously the Reverb (if turned off) would have nothing to do with the sound of the amp in general. He must have biased it wrong and now the amp is too hot and is sitting much closer to the overload point at idle than it should be. The tremelo "doubling back" on itself sounds normal, although it ought to happen at about 5 on the knob setting. There is a complete set of factory service bulletins available for download on this site (in the Manuals section) and a few of them cover proper biasing techniques for the different Music Man amp families as well as properly setting the internal Tremelo trimpot. Steve | ||
| Brian Beebe (brianbb) Username: brianbb Registered: 05-2006 |
I appreciate all suggestions and will report my progress. Brian | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Ok-we should be able to at least point you in the right direction. Mike | ||
| Brian Beebe (brianbb) Username: brianbb Registered: 05-2006 |
Mike, I swapped leads for the reverb tank per your suggestion and I think it fixed the problem with the reverb AND the distortion. I'll know more tomorrow when I can crank it up more. I hope that fixed the problem and I thank you for all your help. Brian |
Tue, 03/25/2014 - 09:29
#1