Pearce G2r Channel Switching Problem

[buffalono]

Hi,

I just picked up a nice solid state stereo amp with built in digital delay and 'verb in a local Craigslist. It sounds really good, I had originally bought it as a clean amp for a Pod HD 500 but I'm really digging the overdrive tone it gets. The only problem with it is the 2nd channel clean channel doesn't turn on unless a phone plug is inserted about half way into the footswitch jack. When I do that both channel leds light and both are active. I've tried connecting a tip ring plug into the footswitch jack and trying the various contacts. The only thing I can accomplish with that is to turn off and on channel 1 and its LED indicator light. I have not had any luck finding a schematic for it and I'm not familier with channel switching amps. I did try some contact cleaner in the jacks but it didn't make any difference. I did find a site that had docs on the amp but unfortunately no schematic. I'm guessing that it must be a jack problem because the channel does turn on when I insert a phone plug half way in to the footswitch jack so it leads me to believe the channel switching electronics are functioning. I didn't have a board mounted switching jack to replace the one in the amp with so I have not tried to sub that yet. Does anyone have any suggestions on how to troubleshoot this issue? I would like to wire up a footswitch for it too since it didn't come with one. The ones I've seen have leds in them. Are the LEDs powered from the same source as the panel channel indicator LED or do I need a external power supply in the footswitch?

[buffalono]

Well I did a little more troubleshooting last night. The Cnannel A and Channel B input jacks seem to be ok, they both show all the jack terminals grounded until a phone plug is inserted. After a plug is in place, one of the terminals lifts from the ground and shows continuity to the tip of the plug.
I also inserted a tip ring sleeve plug into the footswitch jack. If I short the tip and the ring, both channel indicator lights come on and both channels are active. No other combination of terminals connections on the TRS plug made any other change in the channel status indicator lights. Basically the Channel 1 indicator light is on all the time unless I connect the tip and ring terminals of the footswitch plug, then both channels turn on. I'm just trying to get either A or B to be on so I can switch channels. According to the manual this is possible.

[buffalono]

Here is a schematic of a G1 preamp instead of the G2 I'm working on. I'm guessing the same circuit is used for channel switching. The second image is a crop of the channel switching part of the circuit.

[DrGonz78]

Well one thought about why both led's turn on... I had found both versions of the G1 & G2r block diagrams and ch1 & ch2 link right into the foot switch. Turning on both lights w/ the cable inserted w/ the just the sleeve makes me think that it is grounding out the jack that separates between ch1 & ch2 Led lights and their circuits. Have you looked at Q1 or Q2 to see if they are working? Maybe one of those transistors is not making ground correctly? Have you checked other components in those circuits? <<Any of the resistors or diodes? Are you getting 15v? When you ground out the jack and click the channel switch are K1/K2 making any relay clicking noise? Also, G1 block diagram does say right on there "short to ground to turn channel off." Does this amp use both channels in tandem or as you say they should toggle back and forth?

[buffalono]

Thank you for the block diagrams and troubleshooting advice, I'll try out your suggestions over the weekend and let you know how it goes. Your Avatar reminds me I haven't seen Rum Diaries yet, I'll have to check it out this weekend, especially if I get frustrated working on the amp.

[Serdang]

Hi,

I just picked up a nice solid state stereo amp with built in digital delay and 'verb in a local Craigslist. It sounds really good, I had originally bought it as a clean amp for a Pod HD 500 but I'm really digging the overdrive tone it gets. The only problem with it is the 2nd channel clean channel doesn't turn on unless a phone plug is inserted about half way into the footswitch jack. When I do that both channel leds light and both are active. I've tried connecting a tip ring plug into the footswitch jack and trying the various contacts. The only thing I can accomplish with that is to turn off and on channel 1 and its LED indicator light. I have not had any luck finding a schematic for it and I'm not familier with channel switching amps. I did try some contact cleaner in the jacks but it didn't make any difference. I did find a site that had docs on the amp but unfortunately no schematic. I'm guessing that it must be a jack problem because the channel does turn on when I insert a phone plug half way in to the footswitch jack so it leads me to believe the channel switching electronics are functioning. I didn't have a board mounted switching jack to replace the one in the amp with so I have not tried to sub that yet. Does anyone have any suggestions on how to troubleshoot this issue? I would like to wire up a footswitch for it too since it didn't come with one. The ones I've seen have leds in them. Are the LEDs powered from the same source as the panel channel indicator LED or do I need a external power supply in the footswitch?

I dont think you need extra power source as LED lights consumes very less power