Greetings.
I'm looking for Ideas on for a 1993 Fender "The Twin" amp. It works fine except the reverb quit. Is there anyone in this forum that is familiar with the circuit for this amp. My basic question is this: There are 2 12AT7 tubes that appear (to an amateur) to be part of the reverb circuit. There is also a transformer for this circuit. Is this true? If it is true can you tell me how to test the transformer. One of the tubes looks to be barely lit.
My experience: obviously I'm not an electronics expert. However, I did replace the reverb pot on the board several years ago. I'm good at soldering and all the connections are a nice shiny silver, not a cold joint. And the reverb worked just fine. I've replaced my power tubes and properly re-biased the amp before. I understand that the capacitors are dangerous. And I'm ultra careful, never touching wires, or ever working on the amp when it's plugged in!
When using the amp, the reverb has 3 areas where there could be a problem. 1. There is a selector slider switch for channel 1 channel 2 or both. 2. There is the reverb level knob. 3. there is the reverb on/off on the footswitch. So, with the amp on and warmed up, channel selector tested in al positions, and reverb turned all the way up there is no reverb. RCA wires from the head to the spring unit are plugged in. There is a noticeable hiss and a bit of different sound but really no reverb. Footswitch is plugged in and reverb is on. When reverb level knob is turned to off, the hiss goes away and the amp gets quieter. I have the schematic for this amp but to me it's just a bunch of spaghetti. Now if there was someone who knew this circuit, and could tell me to just replace the tubes, or how to carefully test that transformer it would be greatly appreciated.
Beyond that the amp works just fine, I have a pedalboard that can simulate reverb but prefer to have everything on the amp working properly.
Thanks
Jim

I'm looking for Ideas on for a 1993 Fender "The Twin" amp. It works fine except the reverb quit. Is there anyone in this forum that is familiar with the circuit for this amp. My basic question is this: There are 2 12AT7 tubes that appear (to an amateur) to be part of the reverb circuit. There is also a transformer for this circuit. Is this true? If it is true can you tell me how to test the transformer. One of the tubes looks to be barely lit.
My experience: obviously I'm not an electronics expert. However, I did replace the reverb pot on the board several years ago. I'm good at soldering and all the connections are a nice shiny silver, not a cold joint. And the reverb worked just fine. I've replaced my power tubes and properly re-biased the amp before. I understand that the capacitors are dangerous. And I'm ultra careful, never touching wires, or ever working on the amp when it's plugged in!
When using the amp, the reverb has 3 areas where there could be a problem. 1. There is a selector slider switch for channel 1 channel 2 or both. 2. There is the reverb level knob. 3. there is the reverb on/off on the footswitch. So, with the amp on and warmed up, channel selector tested in al positions, and reverb turned all the way up there is no reverb. RCA wires from the head to the spring unit are plugged in. There is a noticeable hiss and a bit of different sound but really no reverb. Footswitch is plugged in and reverb is on. When reverb level knob is turned to off, the hiss goes away and the amp gets quieter. I have the schematic for this amp but to me it's just a bunch of spaghetti. Now if there was someone who knew this circuit, and could tell me to just replace the tubes, or how to carefully test that transformer it would be greatly appreciated.
Beyond that the amp works just fine, I have a pedalboard that can simulate reverb but prefer to have everything on the amp working properly.
Thanks
Jim