Digital Music Corp MX-8 MIDI Patchbay power supply repair

Digital Music Corp MX-8 repair

Years ago I picked up a handy unit called the MX-8. I think I found it for $20 on craigslist. The unit has 8 or so inputs and 8 or so outputs. You can software connect any input to any output. It can do data inspection and changes and other stuff, but all I use it for is basically a multi thru box.

I tend to leave my cheapest synthesizer on all the time, it’s a Roland JV-30. I bought that dead, swapped a diode on the power input and it was good to go. By leaving the keyboard, MX-8 and one MIDI module on all the time I am more tempted to stop and bang around on the keyboard a little.

All this uptime on the little MX-8 eventually resulted in it dying. Hit keyboard key, nothing happened. Figured power loss wiped out the current settings but nope, no power.

First I checked the fuse, but the fuse broke off in the fuse holder and wouldn’t come out. Fuses blow for a reason anyways.

De-racked unit and popped lid off. Was always curious what was inside.

CR-2032 (I think that is the size) lithium battery holds the memory. If your MX-8 forgets everything, this battery is easy to replace and this should fix your issue.

The power issue was a standard ?7805? voltage regulator. It died from heat. The heat is from being left on 24×7 for 10 years. When I replaced it, I re-spooged it with some fake artic silver heatsink compound. For sport, I added a 2nd heatsink behind the factory one so there is a bit more surface area ti dissipate heat.

Unit looks well made inside.

I think the hardest part of this entire ordeal was replacing the fuse holder I broke.

I did consider moving to a switch mode power supply, like from a phone charger. I didn’t have anything handy so I just kept it on the original linear regulator. I could save some heat and power by converting it. Perhaps next time.

4 thoughts on “Digital Music Corp MX-8 MIDI Patchbay power supply repair

  1. Ethan, do you happen to have a schematic for the MX-8 or a service manual? I’ve got a noisy inverter (I think that’s the noise source), and I want to remove it…don’t need the backlight. Any advice or help would be appreciated!

    1. Hello, sorry for late response. I don’t have a schematic as far as I can remember. The inverter/LCD should be pretty standard though? Might be able to move to one that is LED backlit.

  2. Thanks for your info. I have a MX-8 but have lost my PSU. There are no markings on the unit as to what the Power Supply is and nothing in the manual. Could you please let me know the spec of the external power supply, eg is it 9 or 12V, AC or DC, how many milliamps, is centre pin +V or -Ve.

    Thanks in advance,

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