Friday, May 6, 2016

DigiTech MC7 MIDI Controller Pedal repair

The DigiTech MC-7 MIDI Controller Pedal is a standard MIDI program change device.

The MC-7 transmits 1-128 program changes on 1-16 MIDI channels.
I've buy this JUN'91 pedal used for a few Euros. It has a problem on the "c" segment of any of the four 7-segment display.
The repair was quite simple. The integrated 7-segment display lines are driven by  through a 74HC574 octal D-type flip-flops. Signal goes by the 74HC574 through 8 resistors in the 7-segment display.

It takes a few minutes to find which was the "c" segment output signal, simply changing the output channel to display or not that line. Once i've done it, i've checked if the signal goes in to the display... and BINGO!... for the "c" signal it get's interrupted on the soldered join of the display. It's the last join on the right of the below picture.

I just soldered it back, and the display keep working. As you can see.
Pretty simple.
Just for those you are interested, that's the refresh timing for that display.

Adding a cheap USB to MIDI adaptor gives this '91 pedals takes this pedal "Back to the Future".

Thank for Paolo that sells me this pedal board, and a thumbs up to DigiTech support that sends me the 4 pages manual for this pedal, just for completeness.

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