DOD 250 Overdrive Clone Build Research

[Steve Mavronis]

I've been collecting schematics and PCB layouts from around the net for the original grey DOD 250 overdrive. I've also collected plenty of large detailed pictures of the insides of the grey pedals showing the component side, and I found 2 pictures of the PCB trace side from a link on this forum. I noticed how it says 650 on the other side instead of 250 that has already been discussed here. It would be cool to reproduce an authentic clone in all respects, or fallback to some sort of hybrid of the grey 1970's releases.

I'm assuming as some component values changed over the decade, the circuit board PCB layout itself stayed the same? As far as schematics go, my problem is what do you trust as accurate to the original grey 250 circuit, barring minor component value differences?

So I would like to try building a close as possible clone replica as I get enough to go on. My dad (a working 76 yr old electronics engineer/tech) just got me some 741 chips and he can make me professional custom PCB boards too so that part isn't a problem once I get a good accurate example to template.

I checked around to see if there is a close match to the same size box as my DOD YJM308 overdrive since it's also what the DOD 250 overdrive uses too, which is aproximately 4.6" L x 2.6" W x 1.4" H. The closest I've found so far is this 125B Enclosure (4.625" L x 2.5" W x 1.5" H) for $6 from Pedal Parts Plus:


Pedal Parts Plus: 125B Enclosure UNFINISHED

I know there are kits and DIY projects explaining how to make a DOD 250 style overdrive but for some insane reason I want to try to re-create one from scratch by reverse engineering what I can find out about the original grey ones.

[Steve Mavronis]

I'm trying to reverse engineer the original grey DOD Preamp Overdrive 250, including the original PCB layout design, to understand it better. I've been playing around with the free DIY Layout Creator (beta) program for the first time yesterday and after many hours came up with this (unfinished) PCB layout based purely on my photographic research of the grey 250. Think of this as a graphical interpretation of the circuit board photographs:



I can't say this image is accurate yet since I was just trying to copy the layout from photographs and some interpretation (guesswork) was involved. It was just part of a trial and error exercise to help me get used to the DIYLC program, which I think is pretty nice. I know the traces should be on the other side of the PCB, but right now I'm just trying to map out what I see looking at various photos I've collected from around the net. I'm sure some of the trace path connections like underneath the IC chip may be wrong (I tried to cross reference other people's schematics and layout variations) and the diodes may be reversed in my PCB layout since I see them mounted opposite directions in some photographs, which puzzles me.

I'm wondering if those with better grey DOD 250 overdrive knowledge than me could point out any mistakes? Also, on some photographs there is an extra resistor near the bottom of the large curved trace that goes up to pin 7 of the IC. Why does that appear on some grey 250's and not others?