bringing a Boss OD-1 back from the dead...

[amonte]

Morning!

I've got a dual op amp version of the Boss OD-1 from the mid 80's that needs a little (a lot) of help.  At some point, all of the off board components became disconnected and some of the pots lost.  I've got replacement parts, but I don't know what the connections at the top of the board (numbered 1-14) go to.  I've searched the internet for a copy of the service manual but couldn't find it.  I've also started rebuilding the circuit using pictures of the open board and pedal chassis, but that is probably sketchy at best.

Any assistance would be greatly appreciated.   

Thanks,
Jerry

[duck_arse]

if you look the above circuit diagram, each of the connections to off-boards has a little ref number next. it's a fair bet these refer to the board points. is that the right circuit for your pedal?

[amonte]

you know, I had this very same image and COMPLETELY missed the off board designations.  I was able to get it running again, thanks for the help!  still sounds as honky as I remembered it though, so there will be mods coming.   

[Mark Hammer]

As I understand it, there were two issues, the one that duck shows, and an earlier one using a 3403 quad op amp for effect and input/output buffers.  I made one of those and it's a nice little overdrive.  Given that it lacks any tone control, I installed a 3-position toggle that gives stock, a treble rolloff (cap in parallel with diodes), and the same rolloff plus more bass (cap added to C3).

[amonte]

Well, I had success...until I didn't. 

I got the stock circuit working and then replaced C3 with a switch to select between .1, .2 and 1.1uF (two caps in paralell).  The last setting was a bit bass heavy but on lower gain settings it was nice because it preserved the low end (though that 1uF cap might be a bit much).

I also added simple treble roll off tone control between and the second stage. 

Everything was working great at this point.

Then I attempted to add a switch to go from soft to hard clipping diodes.  That didn't work, so I removed the switch.  Somewhere along the way, I must have messed something up because now it's stone dead - no sound when on, no sound when off and no LED.  The strange thing is I'm getting voltage, but something is definitely not right - I'm getting the full 9V at point #3 when I put the positive lead to point #3 and the negative to the ring of the input jack.  I am guessing I have one of the off board leads going to the wrong spot.  I did clip out D5, D6 and D7, but I can't see how that would result in the weird voltage reading I am getting. 

[amonte]

One thing I did want to mention - changing C1, C7 and C3 to .1 and C2 to .047 totally changed the sound.  I always found this thing nasal and thin before that.

[Mark Hammer]

Well, here's what I have: