Bad channel on gl2200

[MiggyParticipant]

I bought a gl2200 32 channel because the price was right. Paid 250.00 and it came in a flight case. The # 12 channel is not working. After seeing how much they want for a mono channel board i think i will pull the board out and try to find the fault. If i leave it on i see the lights on the board go all the way up then drop. Does that about every 5 seconds. Going to look for a bad solder point and then do a test using a audio signal to see how far through the board before signal goes out.

Any Ideals would be much appreciated. Maybe just need to find another gl2200 for a doner.

[Mike CParticipant]

Check the ribbon cable that connects all the channel and master section cards.

There is also a grounding wire that connects through all the boards.

Take the bottom cover off, stand it on one end (have someone hold the mixer
so it doesn’t fall over while your working on it) start proding around the ribbon
cable connections.

Plug in a set of headphones and see if there is a noise associated with the LED’s
flashing.

Check the + and – power supply voltages, you can see where the main power leads come from the supply and connect to one of the master section boards.

[MiggyParticipant]

Ribbon ok. Took out the #12 board. Moved # 32 board to # 12 position. Just did not want to remove power supply again to do my work. # 12 works great now. I did not reinstall the bad board. Left it out for testing. Put a sound signal through it to test pots all pots have 4 solder points. Tested those. All pots allow sound through all four points except the gain pot. It only passes sound through 3 points.will look up a schematic of the gain pot if i can find one.

[Mike CParticipant]

If you did not have the ch12 board connected to the mixer how did you power
the board for bench testing.

You can download the service manual for the 2200 from the Allen Heath website.

I was in my 2200 a couple times, once for a ribbon cable issue and another for a sys link install. I recapped the power supply in another a few years ago.

Off hand I can’t see how a bad gain pot would cause the issue you have, when you had the issue with the LED’s flashing was ch12 assigned to any outputs.

Actually what LED’s on the board were flashing?

[MiggyParticipant]

I hook up a mp3 player to line in and use headphones with end cut off. Aligator clip the headphone – wire to the ground at inputs and use headphones + wire as a probe. I dont think ot is the gain pot at this point as i can set my tester to 20K and watch the numbers as i turn the knob. Not sure how to test those black chips. Seems like something that uses power is coming on then turning right back off. Something that signal goes through because it only does that is when the gain is set high. Lower the gain and it stops doing it. It lights up the leds on the mono channel board and on the main LR meters.

I did notice something odd. When originally checking this system out i could not get the level meters to act independent. I could pan every thing right or left but both meters bounced to sound i put. Now with that board out it has right and left independence. What could go bad on a board that would lock up the meters to each other. All i can think of is something in the pan pot area.

[Author]

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