Strange clock noise in background of MPC60

I'm curious if anybody here has ever heard anything like this. I've had some email communication with VST trying to figure out exactly what it is, and if they know they haven't told me, they've only told me to bring it in and have it checked out. I would like to try and pin down what it is first so I'm not hit with hours of diagnostic charges and then be told they are unable to get parts to repair it. Maybe it would be better to take it to Forat?

Anyway here a link and it's not pretty:

Strange clock noise

Let me break down what you are hearing:
1)the clock noise normalized, so you know what to listen for
2)2 808 kicks the first has the clock noise, the second is clean
3)A blank sample that was used just so the clock noise could be heard better

Does your 60 have maxed out memory? Have you checked inside of it to see? Yours may have a badly done memory hack that is messing with your sampled sounds.

Also try using a diff power cable. It takes a generic computer cable, but I heard those same sounds on mine once & switched cable and it never came up again. Besides that I'd hear if its coming from all outs, stereo & headphones. Keep checking things before you send out cause VST or Forat (although they provide great service) cost $$$.

Yeah it has the memory expansion, everything is factory though, that was one of the first things I checked. It also has the noise on all outputs and headphone jack. I pretty much checked everything I could..... except the power cable. I wish I had a diagnostic floppy for it, then I would have been able to run the CPU and memory tests myself. I have the service manual and I read the whole thing over the weekend. It's all very cut and dried if you have the right tools, which I do since I build analog audio equipment, but I don't have the diagnostic floppy. I took it to VST the other day, so I'll see what they say, funny thing is I forgot to give them the power cable so if that turns out to be the problem, then I guess they won't find anything. Thanks for listening though, I do appreciate the input!

FSK/SMPTE or bus clock leaking into earth and getting into all audio earth paths.

Some thing has come unstuck inside. ( either wiring, chassis mounts or a bad component )

The diagnostic floppy will not help you here as what you are experiencing is not likely to be a problem of RAM. ( unless it's a bad hack job as some one suggested, and all bad )

As an exercise in paranoia...

Check tantalum C12, C13 and C14 on the LSI board. ( C13 and C14 near the EPROMS and C12 right next to the bus harness that feeds the Stereo I/O board )

Check also the tantalum capacitors at the other end of this cable near the PCM77P DAC on the Stereo I/O board.

Tantalum capacitors are evil and they do have a habit of shorting when failed.

Although they could well be ok.

Another thing.

If you disconnect the harness ribbon between the LSI board and STEREO I/O board does the noise disappear from the 8 outs ?

Next ...

You could try a disconnection of the floppy control ribbon to see if its a floppy earthing issue causing the problem. ( The floppy controller shares the same board as the SMPTE chip )

If this MPC60 has had it's drive changed to a TEAC type then the FG jumper may be set incorrectly. ( This could be causing part of the problem )

All I can think of right now.

Rohan.

thanks for the details Rohan, I'm still trying to troubleshoot it. I'm curious because I've noticed another issue in association with the clock noise and that is, sometimes instead of the clock noise I hear a faint string of the samples in memory playing behind the triggered sample, ie. you hit the kick sample and very faintly in the background is snare-closedhat-openhat-tom-cymbal(or whatever is in memory at the time) all strung together.