From:, (Tony'n'Susan)
Subject: DR-55 trig in mod (re: DR-110 tempo sync.)
Date: Fri, 16 Jan 1998 00:11:20 -0600

I did this mod today and it works. It substitutes a trigger input for the
internal clock pulse. The clock IC output goes to the mode switch, and the
convenient jumper lead to use is between the start and stop buttons - it's
hard to miss. So to reuse the (useless as far as I know, except for the
kludgey record mode input sync) jack for the record mode footswitch (FS-1,
J3 on schematic), disconnect the blue wire (goes to tip) and insulate it,
disconnect the brown wires and solder them together. Snip the jumper, then
take the top half (as you look at the unit right side up) of the jumper and
connect it to one of the formerly brown terminals. Connect the bottom of
the jumper to the other brown terminal and connect this terminal to the blue
(tip) terminal.

When there's a trigger input plug inserted, the DR-55 now syncs to that -
the clock is disconnected, and it starts and stops from the trigger. You
have to push start on the DR-55 first, or it only plays the first beat of
whatever rhythm is selected. If you stop and start again from the
controller box, the DR picks up again where it left off. If you hit stop on
the DR without hitting start again, any pulses from the controller will
trigger the first beat. In other words, hit start and stop as usual, even
though it's getting another unit's time.

Being an idiot, I also tested the rim trig 5V out onto the jumper with the
unit in record mode, and I think fried some amplifier transistors in the
Schmidt trigger. Something was smoking, anyway. Guess I'll replace those,
don't think it fried any ICs because a) I can still sort of record patterns
by shorting between two of transistor 15's legs and b) it still plays & all
other functions okay. Oops.

Don't know if this has any relevance for DR-110.

Thanks again to Philip P. for the unit and the schematics (and the parts
coming from Japan...)

Still have that albatross Akai AX-80 if anybody wants to trade for/buy it.