Tweet
I have a Mesa Studio 22 Caliber Plus here in the shop. The treble has barely any effect on the tone, mid has no effect, and bass acts like a slight gain. Owner had replaced the tone control caps with new ones, but obviously it did not fix the issue. Also, there seems to be no clean on this amp when switching channels, just lead and lead at a reduced volume. I reflowed the solder joints from the input to V3, but no change. Any ideas on where to look next?
-
-
Betcha the mid pot ground is faulty."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz -
Mid pot ground is fine, but will check other components that should be going to ground as well.Comment
-
If the tone stack isn't responding and the gain is too high there is almost certainly a tone stack ground fault. If the mid pot ground registers fine from the lug there is still a good chance the lug to resistance strip contacts are bad. What is the measurement from the mid pot CT to chassis?"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
-
8.13k @ 10, 8.7 @ 0.Comment
-
What about the bass pot? Something is elevating that tone stack from ground or perhaps something is wired cattywhompus.Originally posted by psycle_1 View PostLast edited by Chuck H; 07-26-2015, 03:21 PM."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
-
I believe it was the latter (something is wired cattywhompus)... LOL. The lead coming from C41 (.047 uf) was wired to the CT of the bass pot, which made no sense when looking at the schematic. Moved it to the end of the bass pot where it's tied into the CT of the mid control and the BMT controls are now working (although the mid control barely has any effect). Going to compare it to my Studio Pre shortly.Comment
-
Confirmed, it was the miswired pot from the previous repair. BMT act just as they should compared to my Studio Pre.Comment
Comment