When this phase has been reached the power tubes are usually defective and will need replacing. Due to this drift the bias current of the power tubes will gradually increase, and will keep increasing, until the power tubes will glow bright red/orange and the HT fuse will blow (sometimes). This can be difficult to diagnose correctly when the amp is on the repair bench as it can take half an hour or more of testing and/or playing before this bias drift manifests itself. I then tested the 3 LEDs & channels with a guitar via manual and foot-switch operation.The early (1997-2003) Marshall JCM2000 DSL50, DSL100, TSL100 en TSL122 amps are often troubled by an unstable bias (drifting bias). Upon removal of the foot-switch plug, I immediately heard a "click" and the front green LED turned on. I got a screwdriver and forced/bent the end of the metal clip downwards around the tip of the inserted plug. So I inserted a plug all the way in, thus opening the tip "clamp" with the tip of the plug. I found that the tip connector (the most innermost "clamp" ) was not springing back hard enough to create an electrical connection when the plug was removed. SOLUTION: Looking at the foot-switch socket, there are 3 spring-metal "clamps" that open to allow contact with the foot-switch plug when it's inserted. (Although OK via foot-switch)ĭIAGNOSES: All channels switched via foot-switch so I was doubtful that there was a component issue.ĭue to this thread I zoned in on the foot-switch input jack. PROBLEM: Green LED and therefore "Clean Channel" not operating from front panel switches. How I fixed my MARSHALL JCM2000 DSL combo manual channel switching issue. Started to heat up the solder, cleaned evernthing and replaced the C3 capacitor. JCM2000 DSL combo manual channel switching issue of no clean (green) channel.
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