Boss DM-100 schematic needed [EDITED: NEED HELP FINDING A PULSE]

[electric_diaries]

Boss DM-100 schematic needed,

I need a schematic for the DM-100 BBD delay. Does anybody have it lurking around, or have suggestions of other places to try? Google doesn’t know anything about it.

Thanks!

EDIT: Schematic provided by Paradigm X. See below for diagnostic question.

 

[Paradigm X]

hey

http://www.paradigmx.com/dm100.zip

cheers

 

[electric_diaries]

Thanks a bunch Paradigm, It was very helpful!

It appears the problem with mine is that it has no clock signals anywhere. I can’t see a pulse at any of the test points, and I also don’t quite understand how the pulse is generated. I seems to be generated from IC9 and Q18/Q17, and then a devision of that is derived from IC7 and IC8.

Any suggestions of what to try next? Maybe changing Q18/Q17 or the hex inverter?

Thanks!

 

[Paradigm X]

No worries, glad it was useful.

I would suggest trying to change the 4069 as you thought, this seems to generate the clock. ICs 7and 8 seem to then divide it down. I agree with your assessment, but not had this particular issue myself. Im not an expert either but have a basic knowledge, i think...

I know old CMOS can go iffy, might be worth replacing them all. It wont cost much!

 

[culteousness1]

Before changing IC6, check the basic things like supply voltages and grounds of IC6 and IC7.
Is there continuity between IC6-Pin2 to TP1?  If the ICs are socketed, maybe try the MN3005 test circuit on breadboard.

HTH,
Carsten

 

[electric_diaries]

Before changing IC6, check the basic things like supply voltages and grounds of IC6 and IC7.
Is there continuity between IC6-Pin2 to TP1?  If the ICs are socketed, maybe try the MN3005 test circuit on breadboard.

I have checked the supply and grounds of all these chips but at the moment I don't have any reason to suspect that there is a problem with IC6 (also I hope there isn't because they are annoying to find  ). There is no clock signal arriving at TP1 but I think the problem is further back at the clock generator (IC9). Unfortunately everything is soldered directly to the PCB but I will try replacing IC9 first.

 

[electric_diaries]

Ok, I replaced IC9 and I am now getting a clock signal. I can see it at TP1 and also the audio is making it’s way through the switching chips to the BBD input.

However I can’t measure the audio signal on the output of the BBD chip. I am assuming that the BBD chip (IC6) is blown but I wanted to make sure there is nothing else I could check before ordering a new one. They are kinda hard to find and expensive considering.