Anyone dealt with a failed filter assembly?

I picked up a super clean 4K this week. It looks like it was never used! But the output is almost all static (from headphones jack, main 1/4 outs, and XLR output) and the internal audio source shows a strong internal audio signal when nothing is coming in. I tried pulling the ram and nothing changed. When I opened the case, I found that the filter assembly looked strange. One connector was covered with white powder and there's strange goop surrounding the components. Has anyone else ever dealt with this? I ordered a replacement, so I'll update this thread once I've installed it.
Https://flic.kr/p/2qEDGQe

Yes, the connector looks really dirty, but that „goop“ is fully intentional.
It‘s a kind of hot glue to prevent humming of the coil...

A leaking cap in the PSU may be the source of the powder, which (in that case) is likely to be conductive.
You don‘t want that on the main power line and a leaking cap in the PSU is no good either.
Carefully inspect the PSU, but beware:
if the unit is turned on, the (cooler) metal of the PSU is NOT ground, but under high voltage which it can keep for a while even after shut down.

That's interesting. The connector with the powder is on the power cable side of the filter assembly (not the side towards the PSU). How might a bad cap on the PSU cause power on the opposite side of the filter assembly? Thanks!

20250110_125138 by vancurenw, on Flickr

Maybe it was hit with an electrical surge... The PSU looks really clean, but the fuse on it is testing bad. So perhaps a surge blew it out.

A surge blows up for a reason, only very, very rarely by chance.

Regarding the failed PSU cap mentioned above: in most cases some pressure inside the cap builds up while the electrolyte „decays“.
Some caps have cross shaped slits on top, which then open and release content, sometimes a glue-like substance, sometimes gas, sometimes both.
But there are also versions that break at the bottom, which isn‘t visible at all.

So a cap of the PSU can potentially spoil the connector by gas over a distance.
You can simply brush away the white powder, but the true source of the problem is one (or more) caps of the PSU.
Which also are (very) likely the reason why the fuse failed.

You mentioned the MPC looked very clean, which may indicate it hasn‘t been powered on for an extended period of time, possibly 10 years.
Electrolytic capacitors don‘t like this kind of „unpowered state“ and often age faster when never powered.

This kind of failure (imho) is a rather mild form of failure because the MPC at least powered on, though with flaws.
In this case replacement of caps makes sense.

Next stage would be failure of semiconductors in the PSU, which means you can essentially trash it. Unless one is an expert in PSU design/repair...
I‘d strongly suggest to replace the PSU if no knowledgable person is available to have a look on it.

best of luck...
(just keep in mind: the PSU is life threatening, there‘s more voltage in it than mains supply and a failing PSU can break any part of the MPC if it produces wrong voltages)

Thanks, that makes sense to me. But any idea on why the connecter farthest from the PSU would have the white powder on it (and not the connecter closest to, and connected to, the PSU)?

Here‘s a good photo (the last one)
https://gearspace.com/board/showpost.ph ... tcount=322
Shown are 2 caps 400V, 180yF each with supposed „breakup lines“ on top.
Do these look suspect in your unit ?

I have no idea about the white powder, but the fan sucks air (and also gas) out of the case passing over the filter.
But it might as well be simply dust...
In any case: the powder itself isn‘t the main problem, but it can become a part of it IF it‘s based on cap content because then it‘s most likely conductive.

The caps all look good. No visible signs of swelling or any other problem.
[url=https://flic.kr/p/2qEJrqy]
[url=https://flic.kr/p/2qEJrpr]
[url=https://flic.kr/p/2qERb9F]

Yes, the PSU looks really neat, very different from the pic of the filter iirc
I‘d try it with a new fuse when the new filter arrives.
(if the circuit board of the PSU looks significantly different from the rest of circuit boards, it might be a replacement unit)

Replaced the fuse, and now I get no sound in or out at all. Pulled the ram and loaded the program that comes on the factory included CD. It's playing, but no output at all. And no input either. The VU meters do not move. So on to the next problem...

Following some advice I saw on the forum, I removed the effects card, and everything worked perfectly! I could sample from the analogue in and from the CD drive. No fuzz, noise or nothing. But when I tightened everything down, a new problem arose. The screen is black, and no buttons respond on the panel. Only the "Bank A" led is lit. Pushing any button on the panel does not cause any leds to light or turn off (like Bank B, etc.). So I hope/assume that it's a bad connection somewhere. I've reseated the CPU board and the I/O assembly board like 3 different times now, and it doesn't seem to make any difference. Each time I reassemble, I have the same problem again. The connectors between the boards looks great - not dirty or discolored, and no pins appear to be bent.

Normally all LEDs turn on for a moment when the machine is powered up.
Did you check if the display ribbon is properly placed ?

Yes, the ribbon was seated properly. I think the issue is with the CPU board. It looks like it might have been repaired, and the soldering is pretty rough. I'm looking for a picture of the bottom of the CPU board to see what it should look like, but I'm having a hard time finding one.

[url=https://flic.kr/p/2qF4B4A]

that looks really bad
you can‘t go wrong with at least cleaning up the solder joints, which will reveal bad and possibly false connections.