This is a nice compilation of possible (and popular) failure points. ?Of course, it¡¯s also important to take a ¡®do no harm¡¯ approach by logically diagnosing the problems before touching anything. ?For example, you mentioned that your Xpander is ¡®failing all auto-tune tests¡¯. ?Do you mean all tests for all voices? Some voices and some tests? ?The answers can dramatically narrow down the possible causes and cures.
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Perhaps we can develop a trouble shooting tree¡
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One place to start might be to run the auto tune tests on one voice at a time. Once you¡¯ve done this, you can narrow the possibilities. ?Below are some gross assumptions you can make on possible trouble spots, depending on the result of the testing. ?(Caveats: This is not a comprehensive list; More could be added surely! Note that possible causes are only anecdotally listed in order of likelihood to be a cause, based on my experience and reading the forum. Also note, some of the components mentioned below have never been reported to be a cause of problems. I only list them as possible culprits.)
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This can also help reduce some common false assumptions. ?(For example, I¡¯ve noticed a few times in the history of the forum, the CEM 3374s are sometimes the first thing people suspect when there¡¯s any kind of auto-tune failure. But these are not the most common failure point, and should only be suspect under certain types of failures, at the least because they are expensive and rare nowadays!)
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Xpander Troubleshooting Procedure (prototype!):?
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-Turn off all voices but the one being tested: Master Page > Page 2 > Voices ON/OFF.
-Run auto tuning on that one voice: Tune Page > ALL.
-Note which tests failed for that one voice.
-Return to first step, turn off the voice you just tested, turn on the next one to be tested.?
-Repeat for all 6 voices.
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Results:
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Every individually tested voice fails all tests:
- Power supply
- U900 bloc
- U800 bloc
- ICs: U814, U815, U805, U813, U811, U801, U802, U804
- U100 bloc (rare?)
- ICs: U10[2-7] (panning), U108 (tuning comparator), U101 (output op amp)
All individually tested voices fail the same test/s:
- U800 bloc
- Caps: C802, C807
- ICs: U814, U815, U805, U813, U801, U802, U804, ?(U816 RES only)
- U900 bloc
Only some voices fail all tests:
- U[2-7]00 bloc (for that individual voice. Voice 1 = U700 bloc, Voice 2 = U600 bloc, etc.)
- Caps: VCA in/out per voice: Cx49 (common!), Cx47
- More Caps: (power coupling per voice): Cx32, Cx36, Cx38, Cx39, Cx44 (note: ¡®Cx39¡¯ is mislabeled in the Xpander service manual as ¡®Cx35¡¯, middle of page 55.)
- ICs: Ux01, Ux01, Ux06, Ux07, Ux08
Only some tests fail for some voices:
- VCO fail
- Caps: Cx35, Cx37, Cx33, Cx31
- ICs: Ux05, Ux11, Ux10, Ux09, Ux08
- PW fail
- VCF or RES fail
- Caps: Cx48,?
- ICs: Ux12, Ux08, Ux13, Ux15, Ux16, Ux17
- AMP fail
- Caps: Cx49, Cx47
- ICs: Ux15, Ux16, Ux17, Ux12
All Voices pass all tests, but all have muted or distorted sound: (rare?)
- Voice board: U100 bloc
- Pot board: U1
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David, maybe you can run the tests per voice and we can put this tree to the test!
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r1n9o