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 Forum index » DIY Hardware and Software » The Repair Shop
Vintage ARP ODYSSEY MKIII output issue
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gregcomposition



Joined: Oct 20, 2013
Posts: 16
Location: Poland

PostPosted: Fri Feb 23, 2018 3:00 pm    Post subject: Vintage ARP ODYSSEY MKIII output issue Reply with quote  Mark this post and the followings unread

Hi!
I'm finishing the restoration of the vintage ARP Odyssey MKIII and I've got a problem with an output. There's (almost) no voltage on (high) output (~0,02-0,01V). In that state I can't read any frequency so I'm not being able to calibrate the synth Sad
Look at the attached drawing (BTW, ARP used a different capacitor than in the schematic).
I replaced CA3080 with no change. Could be a dead NPN?
Would any of the Odyssey's owners be so kind to check the voltage measurements of their gear?
Any help will be appreciated.
Thanks,
Greg


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DES



Joined: Feb 28, 2003
Posts: 783
Location: New Jersey
Audio files: 8

PostPosted: Sat Mar 17, 2018 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

NPN is certainly worth looking at. Your voltage checks at the output...DC or AC? If DC I would expect what you see...the cap will block DC. Are you able to get any sound coming out of the filter before the 3080? If the NPN checks good check surrounding caps for shorts...I would try and substitute a known good 3080 again. Sometime parts are not always good when purchased...especially if they happen to be recent Chinese parts.
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gregcomposition



Joined: Oct 20, 2013
Posts: 16
Location: Poland

PostPosted: Mon Mar 26, 2018 3:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks, Dave!
You were right - the cheap CA3080 from China was bad. I did not even think that the new one could be bad. It was the first time I had bought not working parts from China, but... I guess there's a first time for everything, right? Unfortunately, I wanted to save the money so I bought 10 packs of them among others ICs. It should have the label: "it may not work - buy it at your risk!".
Anyway, I ordered a new, good one CA3080, I will let you know when I replace it.
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