DOD 680 Analog Delay

[stumper1]

Help.   I got a DOD680 delay pedal for free - it don't work.  Any idea if it's worth fixing?

I get sound in bypass and when engaged I get the dry sound but no delay.  I traced the signal to the input of the 4096 - it appears to stop there. 

Voltages

4096
1   0.00    16   7.57
2   7.51    15   7.50
3  11.39   14   4.08
4   0.00    13  0.00
5   4.08    12   0.00
6  15.14   11   0.00
7  15.14   10  15.13
8   3.38    9   3.16

4013
1   7.51   14  15.13
2   7.57   13   7.50
3   7.93   12   7.57
4   0.00   11   7.93
5   7.57   10   0.00
6   0.00    9   7.57
7   0.00    8   0.00

351 (in place of the TL081 in the schem?)
1   0.01   8   0.00
2   7.92   7  15.13
3   7.59   6   7.93
4   0.00   5   0.00


Schematic:

[cjlectronics]

The schematic shows a +15v regulator...your voltage values for pin 10 of the 4096, pin 14 of the 4013, and pin 7 of the 351 show a negative voltage (-15vdc).  Verify the regulator in your 680 is a 7815? 

CJLectronics

[sta63bmx]

Can you find the "input bias" trimpot marked on the schematic?  With the Electric Mistress I just built, if the bias is wrong, it would pass clean signal and I'd get NO flange effect at all.  I mine, I had a 9V supply and my bias voltage was roughly 3-3.5V, or about halfway between my V+ and PS GND.  What DC voltage is it running at?  I thought the SAD chips had a 17V Vcc, tops.  I don't know, though.

Datasheet...ok, about 18V.

http://www.synthdiy.com/show/getfile.asp?get=880

I bet the trimpot is that one on the bottom left corner in the middle picture here...

http://filters.muziq.be/model/dod/first/680

I'd turn it back and forth while playing and see if you get anything.  I think there's a chip missing in that picture.  Anyways.  Good luck!  Keep us posted.

[stumper1]

The schematic shows a +15v regulator...your voltage values for pin 10 of the 4096, pin 14 of the 4013, and pin 7 of the 351 show a negative voltage (-15vdc).  Verify the regulator in your 680 is a 7815? 

CJLectronics

Sorry for the poor post.  The - were supposed to be dashes not negative V.  Edited the post.  Thanks!

[stumper1]

I did sweep the input bias thru the whole range and still got nothing.  Just tried it again - still nothing .

[stumper1]

BUMP

[stumper1]

Anyone?  Have some time before I start working on an Easyvibe

[captntasty]

I used to have two, one worked the other didn't.  I can't say for sure. but I think the one that didn't work may have had similar symptoms.  The 4096 was blown... I studied up on it at the time (years ago) and these chips were notoriously unreliable.  Finding them today is a challenge and if you do they are $$$.  Just my .02  I hope you find it's something else.

[stumper1]

Thanks