ARP Odyssey 2800 No Sound

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misterc57
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ARP Odyssey 2800 No Sound

Post by misterc57 » Thu Jun 04, 2020 5:03 pm

I am new to this site and have never used a 2800 or any other synth where you need to create your own sounds. I have never worked on one but have experience fixing guitar amps as a hobbyist, I have worked on many amps. Your patience with me is appreciated.

I picked up a first edition 2800. It has no sound. All I hear from the amp is dirty contact noise when pressing keys or moving sliders.

I have been reading some other posts. I removed the keys and gave them a good cleaning, lots of dust balls removed. I sprayed all the sliders. No change in the behavior.

I read about bypassing the 4023 filter with a jumper cable at pin 1. Tried that but still no change in behavior.

I confirmed the voltages of the 4023 on pins 6, 7, 8 : -15 vdc, 0 vdc, 15 vdc

Would love to get some help to find the problem. Perhaps direct me to test points to signal trace for sound.

I am attaching a pic showing the settings I am using. I have run the sliders up/down on the audio mixer and the vca.

Thank you! MarkO
IMG_20200604_102551114-forum.jpg

synthchaser
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Re: ARP Odyssey 2800 No Sound

Post by synthchaser » Fri Jun 05, 2020 3:17 am

The service manual has 6 pages of test points listed, with illustrations of what waveforms you should be seeing on them with your scope. I'd check it out before trying to fix anything. And spraying these sliders is a bad idea, there are some good videos on how to clean them.

misterc57
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Re: ARP Odyssey 2800 No Sound

Post by misterc57 » Fri Jun 05, 2020 3:45 pm

Where are the test points on the boards? I am looking at the service manual test point check list.

Looking at the bottom of Board A. Are the test points (TP) labelled on the board? I do not see them.

Thank you

synthchaser
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Re: ARP Odyssey 2800 No Sound

Post by synthchaser » Fri Jun 05, 2020 6:23 pm

They didn't want to make it easy on anyone, they're not labeled on the board. The test points are listed on the schematic, and you need to figure out where those parts correspond to on the PCB using the PCB layout diagrams.

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