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SDD1000 halfway fixed (only short delays) Reverb/Delay Processors (HW)
Old 4 weeks ago
  #1
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SDD1000 halfway fixed (only short delays)

I got a Korg SDD1000 for $20, wich is probably all I need to say about the condition it was in. It had low, distorted output but passing a signal and responding to knobs.

I replaced a faulty 4558, wich solved most of the problem. The first three short delays work just fine now. The last three knob-positions are still 'in a bad way'.

The longest delay and 2 sample/rec knob positions have this loud, distorted audio. It's a very loud signal compared to the other 3 knob positions.

Any ideas? I've been referencing the sdd2000 service manual since that's all you can find online. I'm not even sure which chip(s) are doing the delay, but if it uses a second chip for the longer times it could be that? I'm trying to figure out which components would only be involved in the longer delays. It isn't just the sample/rec but the longest delay as well.

Any info or ideas would be appreciated. These units are dope, so I really want to get it working.

Thanks!!
Old 4 weeks ago
  #2
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acreil's Avatar
 

Check the RAM ICs and look for bad solder joints or broken or corroded traces.
Old 4 weeks ago
  #3
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Thanks for the advice.

I went searching for the RAM chip, but found a broken lead instead. Patched that up, and it made the circuit feel much more stable, and the dry signal seems a bit cleaner.

Unfortunately, the delay signal is also gone. All of them, including the short delays that were working before. The delay signal has come back several times from randomly probing the delay chip pins, so hopefully it's still alive in there somewhere.

I hit every suspicious looking solder joint on the digital board, but that hasn't changed much.

As far as the RAM goes, I'm embarrassed to admit that I can't find it. Pretty sure I've googled every chip on the digital board, but nothing sounds right. Both the sdd1200 and sdd2000 docs have some version of 4164 chips listed, but I can't find any of those either. I'm a noob and all, but I should be able to find the RAM...

The 4 delay chips are making a digital oscillation on the output pins and freq is contollable by the knobs, so I think they are ok? Sounds pretty fat TBH.

I guess it's possible I fried the multistage d/a chip or something else while probing with an RCA/speaker. Not really sure if that's bad to do. Some of those pins have nice distortion, and I was definitely shorting pins by accident. Some of the sounds were insane. Going back to virtual distortion is going to be tough...
Old 4 weeks ago
  #4
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Found the RAM chips. 4 x mb8264 chips that I somehow thought was something else...

They are getting a proper voltage, and all the chips have the same pin-frequency relationship when I listen with an RCA. Not quite sure how else to test them.

I might redo the fix on the broken lead just to be safe.

There is a 3014 opamp that sounds wierd but I don't see why that would kill the whole signal.

Any thoughts, opinions, or general anecdotes would be greatly appreciated.

Thanks!
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