Help needed 2205 won’t change channels

[Lizzy]

I have a 1987 vintage JCM 800 2205 that will not change from gain channel back to clean. It had this problem a while back when I first bought it used off of eBay and I had a tech fix it (not sure what he did) but now it is back again.
I had been using a standard 2 button Carvin FS22 (no lights/leds) to change channels but I also have used the 2 button footswitch that came with my Marshall MA-100h which does have lights. I was thinking perhaps using a footswitch that has lights on it may cause the problem. It will not change channels with either footswitch presently.

I’m wondering if this is a known problem with the 2205/2210’s and if so what is the fix?
I will probably have to take it back to a shop to repair but I’d still like to have the knowledge of what they should do to resolve it so I can make sure the correct fix is applied.

Thanks!

[surfnorthwest]

Marshall part number PEDL10009

http://shop.marshallamps.com/products/p ... .0.0?pp=24&

[pleximaster]

Very common on these. The switching circuitry is controlled by a IC chip that runs a big capacitor (330uF electrolyte i think) that acts as a "spring" holding the channel instead of a relay. It could be either the capacitor or the IC chip that needs to be replaced. Increasing the capacitor helps temporarily then the IC dies for sure. I don´t remember the particular IC chip but I think its printed on it. The unit is not made any more but there a million of these on eBay for a buck or two. Have a tech replace both. Heads up some PCB boards of the JCM800 area are very fragile and one should be very careful when working on them!!!

I am having the same issue on one of my split channels got the chip and the capacitor but not the time... I got to get a soldering gun for IC chip as well otherwise I could have made an illustration. I don’t use the clean channel much anyway and it’s the dirty that’s on default.

best plexi