JCM 900 Dual Reverb Effects Loop Problem

timberlin · Newbie Alert Joined: 11 Oct 2008 Posts: 1

Hi all,

I have two (probably related) problems on a JCM 900 4502 combo. It works perfectly apart from the following:

1. The effects loop is louder (around twice as loud) in channel a then channel b. Delays jump in volume when switched from channel b to channel a.

2. The onboard reverb (accutronics) does nearly the same. When switching from channel b to channel a the reverb jumps in level and then settles to the level that it would normally have on channel a. This made me think it might be a cap draining for some reason. Switching to channel b does not give this effect.

As I said, the dry tone and volume is not affected at all (and sounds great actually) whether the reverb or delay is engaged or not.

Mine is modified in the pre amp. The diode bridge (BR2) in channel b has been replaced by a 100K resistor to ground and the LEDs (1-4) in channel a have been replaced by a 220K resistor to ground. Apart from that it's all original.

Any info would be really appreciated.

Cheers!