Thanks. Yeah, I have that schematic as well. I’m no expert but I don’t see a CD4040 in this circuit. The only ICs are the one M252B1BW which seems to be the brains, 4 EH104B’s, and 5 RC4558N’s. No counters or other things that might be clocky. But maybe one of these other ICs can be used that way and someone out there with more knowledge than me knows a thing or two.

I’ve tried tracing back the clock in on the M252 (http://www.milton.arachsys.com/nj71/pdf/m252.pdf) but I’m not knowledgable to enough to figure out where that signal is being generated and therefore, how to interrupt it and send in a different clock source.

Maybe, I’m just thinking out loud here, I use a scope to try to figure out what kind of signal is present at the clock input and then build a little external circuit that I can use to take DIN sync or the like and convert it to whatever the M252 wants to see.

But I’m hoping there’s just some unused parts of the circuit that I could wire up as the clock in, where there’s over versions of the DRM 15 that have the clock in. I’m hesitant to randomly circuit bend it but maybe that’s my only hope.