Musicians Roadhouse

NAD today! Got this 1990 2205 and have a few questions. First, the amp works and sounds good, I didn't get the foot switch with it but tried my Vintage-modern switch and got response, just don't know if it's working correctly. Definitely has had some work done to it (to be expected for a 25 year old amp). The amp turns on with the channel LED not lit, when I plug in my guitar it turns red to the "Boost" channel. I have a 2 button push-click/push-click from my VM, the reverb turns on and off but I have to hold the button down to get the clean channel? Also, the Intersil CA3046 chip seems to have been replaced with a NTE 912 equivalent. I've attached some shots of the channel switching jack as it looks as though some caps have been added, not sure though. One area that definitely looks to have been modded is a large cap coming off the board and going to ground.

Any comments would be appreciated,

Ken

I have 1987 2205 and I can say they are very finicky about footswitches. Mine doesnt like any foot switch with lights for some reason, tried a couple Marshall MA and Traynor 2 button switches with lights that didn't work very well with it. Carvin FS-22 without lights works perfectly.

I think 1990 2205's are a somewhat rare find so congratulations!

The caps in the footswitch jack could have been added to stop or reduce "popping" noise when utilizing the switch.
As far as the chip replacement i wouldn't be too concerned, a ca3046 is just a 5 transistor array on a single chip used for channel switching in this amp.

As far as the big cap, it appears to be there to provide filtering for probably some power supply line, but it's hard to say just from that small pic.

Another thing i'm seeing here is the channel switching is powered from the heater winding. A tube short could really put the screws to that part of the circuit.

Here's a few more concerning that big cap in question, the "red" wire goes back to the pcb