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DOD 690 Chorus broke..


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10/4/1999 7:04 PM
Dave
DOD 690 Chorus broke..
Hi,  
I have an DOD 690 chorus that doesnt have any effected signal. The indicator LED flashes w/ the LFO speed which lets me know its not the LFO thats the problem. What do Yall think it could be??  
Thanx,  
Dave
 
10/4/1999 8:02 PM
R.G.

I'd check, in order:  
1. delay chip clocks at delay chip  
2. signal into delay chip  
3. signal out of delay chip  
4. opamp power supply voltages  
5. opamp bias voltages at no signal.  
 
10/4/1999 8:32 PM
Mark Hammer
Since all similar delay-based effects work by combining straight and delayed signal, it is common to find designs using a switching system that simply brings the delay signal in and out of circuit at the final mixing stage, without turning anything off or bypassing the effect overall. You can APPEAR to have turned the effect on and off, and nothing has changed (i.e., you still get straight signal only). I have a busted MXR Commande Series Flanger that does exactly that - the LED lights up appropriately, but damned if you get anything other than straight signal out of it.  
 
So, to RG's list I would add "Check the switch and/or switch circuitry".  
 
Given the age of the unit, it is also possible that the bias trimpot has drifted and the BBD chip is not getting the DC offset it needs to carry signal through.  
 
There is an old Craig Anderton mod to this pedal which involves one component and extends the overall delay range into passable flanging. I'll see if I can find it at home. It was posted in DEVICE magazine 20 years ago.
 
10/9/1999 1:42 AM
matt

Hi,  
I've got one of these as well,and it was doing the same thing when I got it(for free as well!),It turned out that there were quite a few broken and corroded tracks on the PCB,and could only be picked up with a magnifying glass.Maybe this one has the same problem.  
I cant remember which tracks they were,as I didn't do it myself.It was before I knew anything about fixing them.  
 
Matt  
 
 
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