Hello yall,
I have an old silver face twin that is a real work horse (backline rental for 30+ years!) and playing great, except for this fizzy sizzle distortion that rides the reverb decay. Reverb on zero sounds like any decent working dry twin. Normal channel of course has no issues.
I have swapped in new tubes with no change , so I am assuming it’s either the reverb tank itself failing or a failing component in the circuit itself
Before I spend the time to tear into the thing, or possibly order a new reverb tank, I thought I would ask the experts first what y’all thoughts were on the matter and hopefully diminish any tail chasing headaches or unnecessary expenses .
Appreciate the help. Thank you for the time
Charlie
Twin Reverb; Reverb issues troubleshooting
Moderators: pompeiisneaks, Colossal
-
- Posts: 1065
- Joined: Fri Apr 16, 2010 9:04 am
- Location: Santa Cruz, CA
Re: Twin Reverb; Reverb issues troubleshooting
A good way to rule out a failing part(s) would be to take voltages at the plate and cathodes on the driver and recovery tubes and see that they match the expected value (within 10-20% or so). Also check coupling caps for DC leakage. Tank could be starting to go though, as you mention.
-
- Posts: 4627
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Twin Reverb; Reverb issues troubleshooting
One way to rule out a bad tank is to just disconnect it’s send and return cables and then jump a 470k resistor across what would be the tips of the RCA jacks.
Doing this will just make the reverb circuit a volume boost circuit.
If this fails I would change out both the plate load and cathode resistor in the recovery gain stage and also that 3.3 meg mixer / level matching resistor.
I would also just shot gun the 2.2 K cathode resistor and the 1meg grid resistor on the 12AT7 pan driver.
Doing this will just make the reverb circuit a volume boost circuit.
If this fails I would change out both the plate load and cathode resistor in the recovery gain stage and also that 3.3 meg mixer / level matching resistor.
I would also just shot gun the 2.2 K cathode resistor and the 1meg grid resistor on the 12AT7 pan driver.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Twin Reverb; Reverb issues troubleshooting
We're assuming you've already deoxidized the pan, chassis and cable connections.
Tube junkie that aspires to become a tri-state bidirectional buss driver.
-
- Posts: 1065
- Joined: Fri Apr 16, 2010 9:04 am
- Location: Santa Cruz, CA
Re: Twin Reverb; Reverb issues troubleshooting
Thank you all for the education.
Yes, All connections have been thoroughly cleaned .
Thanks steveM , The 470k resistor across the jack caused the volume increase with reverb knob , so it must be the reverb tank (?)
Gonna order up a new tank
Yes, All connections have been thoroughly cleaned .
Thanks steveM , The 470k resistor across the jack caused the volume increase with reverb knob , so it must be the reverb tank (?)
Gonna order up a new tank
Charlie
-
- Posts: 4627
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Twin Reverb; Reverb issues troubleshooting
Yes, the new tank will get you back to good!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!