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Do all voices still fail all tests after replacing all of those components?

I will check your suggestions. In my case, each individual voice fails, when tested one at a time. When "All" is select, they also all fail. I did find 2 bad CEM3374's that were not outputting the

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

Hi there, Just to let you know that I replaced? cd4053 (ic 904 if I remember well) and the tune is now working... Thanks for your help there are loads of good advice to read here...

What is in file section is laters version. Only this post is older version. --- /g/xpantastic/files/Documents

Is it possible to delete the older versions?

I uploaded a newer version with all precautions in the files section. *Re: Xpander Auto-Tune failures*

Hi Burt Great idea to keep a cheat sheet. When you think you've got the final version done, it would be good to put it in the files section. This way, when people need to troubleshoot they can just

I have an Oberheim Xpander (v 14. ROMS), which is failing all auto-tune tests. I have read every post related to tuning back to 2008 and have developed a game plan. I am posting here, please feel free

I had a failing voice, tunepage showing "fail" already for OSCs, w/ my Xpander last year. I?m 1st owner since 1987... Can be I posted before @ (Yahoo) Xpanatastic,- but the culprit was a tiny TL0XX

That's great to hear! ?(I'll wager U814 was the problem, since the failures were in specific CV categories across all voices.) Regarding the new problem, perhaps the new IC's are simply revealing a

Well, that was a lot of information. And good information, too! I've been quiet so far because I've waited for replacement parts which now have arrived. So I first swapped several of the 900 group of

I've been tracking down some subtle tuning issues myself, and have been thinking along the same lines as your zero-crossing hypothesis. ?Here’s few things I've learned along the way. ?I can’t

Yes, I did all memory checks and also verified 4v reference and DAC Offset.

Maybe too obvious, but have you tried any of the calibration tests in the service manual? ?(Relevant might be the "MEM", "VMEM", 4v reference, and DAC calibration tests.)

In recently researching IC replacements for the Xpander, I've noticed that TI's own datasheets sometimes offer seemingly conflicting info about the LS/HC/HCT series of chips. ?But, it turns out,

It couldn’t hurt to swap out the 8253 as well as U915 (LS139). Seeing an analog signal going into a digital chip will give me pause to think, If you had analog muxs, VCO and VCF chip fails, maybe

I had thought about U921 too; however according to the service manual it's also used for VCF calibration - and that works every time. I'd be interested to learn more about the tuning process. For

Hi Off the top of my head, Maybe U921 or it’s connected glue logic. This timer chip is used for both vco tuning and PW Calibration. - Karl Sent from Mail for Windows 10 Sent: Monday, June 8, 2020

Addendum: I'm also a bit irritated by the different logic families present. Most chips are 74LS; and from the service manual I know that 74S and 74C also were used. However I've noticed a number of