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Boss DM2 schematic

2/24/1997 8:45 PM
Chris Russo
Boss DM2 schematic
Does anyone here know where I can locate a schematic for a Boss DM2 Analog delay.  
I need to repair one. (inop when powered by wallwart)  
Thanks in advance for any help ! :D  
2/25/1997 6:45 AM
Mark Hammer

Don't have the schematic, or even a peek inside a DM-2 but, much like  
early tube amps, the small number of chips that can serve as the "engine"  
of an analog delay reduce the degrees of freedom, and make guesswork pretty easy.  
If the problem is a power problem, one of the things to consider (and I mention it just to rule it out) is the polarity of the plug. Wall-warts vary in their polarity. Some have the outside (shaft) negative and some have it positive. You might want to measure yours (assuming it's not and official Boss adaptor) and see what the polarity of the plug is. Boss (and many other devices that take +9vdc with a pin jack) wants +9vdc on the *outside*, and ground on the *inside* (i.e., the "hole"). My sincere apologies if I'm underestimating the complexity of the problem. Just want to rule out the simple stuff.  
Please note that with very few exceptions, many stomp-boxes that run off 9V batteries can also be run off even larger voltages (e.g., a 12-15 volt adaptor). The extra voltage generally gives them more headroom before clipping, so if the device works best *when* it's clipping (i.e., a distortion device), 9vdc may prove better sounding to some ears than others.
2/25/1997 10:48 PM
Chris Russo

Thanks for your reply. Yeah, I understand the polarity issue. The design of the DM2 has the positive side of the battery connected to a "switched" power connector(sleeve), such that the battery is switched out when the power supply connector is inserted.  
The area of confusion is the neg. side. The battery's neg. side is switched in by inserting the audio input connector. The power supply's neg.,however, is wired directly to the PC board and appears to go to a resistor, probably current limiting.  
This is the point I stopped "poking". A schematic would be be very helpful. Besides being one of the better delay's I've heard, this one is also NOT mine ! So I'd like to get it fixed without destroying anything. My own analog delay is a DM3 which  
appears to be configured differently. Again thanks for the polarity reminder.  
3/6/1997 7:34 AM
Mike Tatro

Hi Chris-  
Lemme aske a stupid question (cause I've has a similar problem) when you're testing the DM-2 do you have it fully connected (input and output connections with guitar and amp?)  
The reason I mention this is that I power many peadals with the same power supply on my pedal board (in this case I use 6 C cells instead of a wall wart).  
Here's my path:  
Guitar->CS-3->TS-808->MESA V-Twin->volume pedal->DM-2->DM-3->Amp input  
All pedals are powered bu the same power supply. IF I break any of the input connections the DM-2 and DM-3 don't power up. Obviously, the signal ground is being used for power ground . This seems to be the as-intended design. On paper, this would seem to be VERY undesirable, but since it works and I'm not getting excessive noise (my rig is VERY quiet for a full vintage analog rig), I don't worry about it. But yeah, I too thought I had a bad DM-2.  
Lemme know.  
FYI, I much prefer the DM-2 to the DM-3. I'm intersted in trading my DM-3 for a DM-2. If you find that the DM-2 is OK, are you interested? I'm in the LA/Orange County CA area.  
8/6/1997 6:29 AM
CJ Landry

I have seen this problem on many pedals. They way the problem is described is telling me that the pedal works with the battery but not with the power supply wall wart. The solution to this problem lies in the power jack in the pedal itself. The jack gets broken away from the solder connections on the PC board and causes the loss of input supply voltage when you use the wall wart. Retouch the solder connections in that area of the power jack and this should solve your problem.  
Sorry for the late response to this post.  
12/2/1997 10:56 PM
paul kreimer

the DM-2 requires an old boss adapter to work. I doesn't work with the newer style boss adapters.
12/3/1997 7:16 AM
CJ Landry

Now you got me curious??? What is the difference in the old style PS and the new style PS. Is the plug different? Sometimes I have a lapse of memory functionality..  

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