MPC60 emits noise (old transformer?)

Just got an MPC60 MK1 with a high pitched humming/beeping sound coming from it. I'm suspecting the transformer or might it be related to the almost dead backlight? I imagine it would be pretty hard to get a new transformer... Any ideas/tips highly appreciated.

Common issue.

Have you tried to search this forum or read the MPC60 bible thread?

Just to be clear where is the noise coming from? Is it inside the machine or leaking into the outputs? Have you opened the machine to pinpoint the source? See that little box to the rear of the floppy drive, most likely your culprit. The invertor for the screen. Disconnect it completely to see if there is any difference, then report back.

Yes, you were right, the inverter was the culprit. Thank you so much! It was such a relief to get rid of the noise. The MPC went completely silent.

I just ordered a new backlight from midi-rakete.de. Do you think I should try to isolate the inverter to keep it from resonating, or should I go for a new one (if that's possible)?

If the inverter is the problem you should get a new one.
If you change only the backlight you'll still have a noisy inverter powering it.
Isolatiing the inverter will make it quieter but probably not silent.

Thanks for the reply.

It seems that I accidentally must have broken the MPC-60 while disabling the inverter and tinkering inside. When I try to sample, I get a very distorted albeit quiet sound, and the recordmeter indicates that there is sound coming in, although it's quiet.

What a nightmare!

Reconnect the invertor first to see if the noise is related to disconnecting it.

Yes, I've reconnected the inverter, and it is definitely making the noise. A really loud whining high pitched screaming noise that is.

I also discovered that the diskdrive won't read my old disks any more, but it can format new ones and write and load from those. The metronome doesn't sound at all, and samples sound completely off, as I described earlier. I wonder if I accidentally fried some chip with an electric discharge.

Ok so we've established that the invertor is probably shot.

The next issue:

ZX81 wrote:When I try to sample, I get a very distorted albeit quiet sound, and the recordmeter indicates that there is sound coming in, although it's quiet.

Does your machine have a RAM hack (DIY)? Is the RAM expansion board (if there is one) seated properly? Are all cables and EPROM's seated properly? Anything inside look unusual? cold solder joints? disconnected/missing components?

Where did you get this machine from, and were you made aware of any 'issues' with it beforehand?

ZX81 wrote:It seems that I accidentally must have broken the MPC-60 while disabling the inverter and tinkering inside. When I try to sample, I get a very distorted albeit quiet sound, and the recordmeter indicates that there is sound coming in, although it's quiet.

Did you accidentally move the rear panel REC IN GAIN switch to a different position than what it was previously set to?

Have you tried sampling with the REC IN GAIN switch in each of the three possible positions, to see if it returns it to operating the way you expect?

Thank you for your help, guys!

It's definitely related to me tinkering inside when disconnecting the inverter. Aside from disconnecting the inverter, I removed the big board with the transport buttons etc just to have a look at it (was going to replace the tact-switches later), and disconnected the diskdrive briefly.

Now the diskdrive makes a constant noise when I have a disk inside, and I can't read/write to my previous disks, but can write to new disks. Wierd. According to the previous owner, the disk drive was recently replaced. He also stated that the memory expansion is in fact the original one, but I haven't visually verified this. Will do that when I get home later this evening.

It's not related to the rec in-level. The distortion is not just regular distortion, it sounds completely whack, and the output is also lower than usual. When I don't have anything connected to the sample input, the input level meter in the sample screen is half full.

I got hold of the service manual, and will be running some tests when I get home and report back! I really, really hope to get it working again... For the week I had it, it was sort of a love affair.

I suppose the lesson learned is to try and deal with one issue at a time if you are unsure what you are doing. And don't remove circuit boards just to have a look, do that only if it is necessary. These old machine are fragile and often unpredictable.

Hope you get things sorted!

Hurray! It was just a connector that was a bit loose, and now it's working perfectly again! The relief...

Clint: Yes, good advice to be systematic.

Now I'll need to get a new inverter, change the tact switches and get a new start key.

OK, after reading up a little, this is what I got for the MPC60:

100 tact switches, $9: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... OC:US:3160

Floppy emulator: http://www.ebay.com.au/itm/ws/eBayISAPI ... 500wt_1139

Inverter for foil: http://www.ebay.com.au/itm/330886105709 ... 167wt_1265

New foil: http://www.midi-rakete.de/eng/elfolie.htm

Lots of knowledge and good information in this forum - thanks!

ZX81 wrote:OK, after reading up a little, this is what I got for the MPC60:

100 tact switches, $9: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... OC:US:3160

I would be looking for quality name brand tacts, Alps or Omron for example.

ZX81 wrote:Floppy emulator: http://www.ebay.com.au/itm/ws/eBayISAPI ... 500wt_1139

I prefer the MPC60 SCSI option with a CF reader.

ZX81 wrote:Inverter for foil: http://www.ebay.com.au/itm/330886105709 ... 167wt_1265

Not really a direct replacement in terms of specifications, for example...
- 6-12V DC input, MPC power supply outputs 5VDC, no idea if it works at 5VDC
- an output of 77VAC at 6VDC, no idea what AC voltage it outputs at 5VDC, original is approx. 95VAC
- an output frequency of 3 kHz, original is approx. 500-550 Hz
- maybe a little over sized for an MPC EL lamp? "Unused (NEW) inverter specially designed for powering EL lamp up to a A4 or 400 sq cm size"

SCSI seems like a very expensive option, considering the board is not manufactured by Marion Systems anymore. Or have I missed something here?

The inverter was recommended by user micb in this thread: viewtopic.php?f=4&t=164886

He states that it works alright in his machine. And if the backlight would go out earlier than expected, they are still pretty cheap.

I see your point about the tact switches though. I'll report back in 2030 to tell you if they still work by then.