Tweet
Hello,
I have a 2 Marshall JCM 900s that have issues I'm trying to resolve.
The first one is a 50 Watt that has a crackly sound on channel A. I checked all solder connections and tried different preamp tubes (both channels and phase inverter) and that didn't solve the problem. Channel B works ok. Could there a bad component somewhere on the channel A circuit? Where to start?
The second is a 100 Watt that's only at half-volume. My first thought would be the output transformer, but when I look at the power tubes, 2 of the four have somewhat of a dimmer glow and the other 2 seem normal. Neither tubes are red-plating. You have to turn the master volume up to about 12 o' clock to get a decent stage volume which doesn't seem normal being that the 50 watt is louder. This customer didn't change the tubes since he bought it. This may have damaged other components in the circuit. I would like to know where to start as far as being able to resolve this issue. Any suggestions? Thanks!
I have a 2 Marshall JCM 900s that have issues I'm trying to resolve.
The first one is a 50 Watt that has a crackly sound on channel A. I checked all solder connections and tried different preamp tubes (both channels and phase inverter) and that didn't solve the problem. Channel B works ok. Could there a bad component somewhere on the channel A circuit? Where to start?
The second is a 100 Watt that's only at half-volume. My first thought would be the output transformer, but when I look at the power tubes, 2 of the four have somewhat of a dimmer glow and the other 2 seem normal. Neither tubes are red-plating. You have to turn the master volume up to about 12 o' clock to get a decent stage volume which doesn't seem normal being that the 50 watt is louder. This customer didn't change the tubes since he bought it. This may have damaged other components in the circuit. I would like to know where to start as far as being able to resolve this issue. Any suggestions? Thanks!