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stahlhart
Platinum Member
1318 Posts |
 Posted - 11/03/2005 : 21:51:15
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I recently won an eBay auction for this MIJ DD-2, which I got cheaply (about $50), but unfortunately it's internal wiring has been tremendously hacked. I was given assurance that, apart from the wiring issues, it was a working pedal... I have my doubts at this point, but I was in the market for a couple of these units, and this one was pretty cheaply priced, and I have worked on electronic stuff for a few decades now, so I figured that I'd roll the dice on this pedal, and who knows, mabye i'd luck out and get it working -- and I'm not out too much if I don't.
Anyway -- here's a list of what I'm up against:
-- the battery clip is missing
-- power and ground wires have been cut and spliced in several places
-- the case LED is missing
-- some input and output signal/ground wires disconnected
The boards are intact and unmodified, thankfully, apart from what looks like some of the wiring to and from the input and output jacks having been messed with at some point (the solder joints are not original.
Initial questions I have, in case anyone has one of these or has ever looked at the insides of one:
-- there's a separate green wire coming off of the controls board -- I am guessing from comparing to the schematic that this is one of the LED leads?
-- the signal to the effect output jack runs through a shielded cable. How is the shield connected, if it is connected, on the board side?
I think that initial my plan of action will be to (1) replace the battery clip, (2) restore the DC (+) and ground wiring to original state, (3) replace the missing LED (I have a spare), and just see if I can power the effect on and off from the footswitch, using the LED as an indication. From there, I'll see if I can restore the signal paths to the input and output jacks and then test the effect with an actual guitar signal.
Also: there are a couple of trimpots inside -- I've seen one on the main board and one on the controls board so far. Does anyone have the instructions for how to adjust these, in case they have been tampered with at some point (considering what the condition of the pedal was when I got it, I would not be surprised if they were).
Any assistance or feedback would be greatly appreciated (walrus121?).
C.K.
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 11/03/2005 : 22:17:58
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$50 sounds like a good price if you can get it going again. Getting the wires in the right place might not be as difficult as it sounds. It sounds like you have the schematic already. For every wire there's a number printed on the schematic. This number is also printed on the PCB so you can use this to get them connected correctly.
I don't have the part of the schematic that covers the trimpots. They're labelled clock low and clock high on the schematic so I guess they're for fine adjusting the clock frequency. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 11/03/2005 : 23:03:10
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I was hoping that a service manual for the DD-2 existed, as the adjustments are usually covered on those (I have one for the original MIJ DS-1 that has 'scope output waveforms and such).
The things that are scaring me the most right now are (1) that DC polarity may have been reversed on this pedal, given that the battery clip was removed and black/red wires were cut, meaning that it was put on an AC adapter or some other DC-from-AC power on the external power jack, and the wiring to that jack was modified; and (2) the trimpots may have been tweaked at some point.
In the old days they used to "lock" the trimpots in place with a dab of paint, and even if that seal was broken at some point you could use the two halves to approximately put the adjustment back.
You're right; the identification of the wiring points is helping tremendously. At the ripe old age of 45, I now need a magnifying glass to read them  , but I'm managing.
I'll keep you posted of my progress here -- thanks for the response...
C.K.
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 11/03/2005 : 23:42:43
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In the 80s I used to run a radio/tv repair shop. Whenever I'd adjusted a trimpot I used to lock the setting using nail polish. I still remember when I bought that bottle...
- Hi, I'd like to buy a bottle of nail polish, please.
- Sure, what colour would you like?
- I don't care. What's the cheapest you got?
- Eeeh...., well... this series is very reasonably priced...
The poor girl in the store didn't know what to believe. I never told her that it was never going on any finger nails  |
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stahlhart
Platinum Member
1318 Posts |
Posted - 11/07/2005 : 06:33:04
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Apparently someone did damage the power supply.
Got most of the tampered wiring corrected, at least enough to power the unit up with a battery -- and the battery overheated.
Removing D6 corrected this problem, and now I've got a working check light that I can toggle with the footswitch.
I don't have servicing information beyond the schematic, so I can't do much with the Roland part number for D6, but examination of the schematic suggests that it's probably nothing more than a 9V zener. The circuit probably don't even require it when run on a battery; I'm guessing that it's there for the AC adapter.
So that was probably why the previous owner bailed on it. But it does seem that, since IC10 (the TO-92 5VDC regulator is okay, mabye the diode just shorted when the power wiring was tampered with, and none of the short circuit issue made it to the rest of the circuitry.
More later...
C.K.
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stahlhart
Platinum Member
1318 Posts |
Posted - 11/07/2005 : 06:49:01
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And the DD-2 has come to life... 
I jury-rigged it to the line input of the sound card on my PC (the amp is in need of some work at the moment), and though there appears to be some sort of a shorting issue with the input cabling -- the signal from my guitar was cutting in and out -- I am getting delay on the wet output.
Back to the workbench to see what the problem with the wiring might be.
C.K.
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stahlhart
Platinum Member
1318 Posts |
Posted - 11/07/2005 : 07:20:50
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Apparently the input signal issue was nothing more than some corrosion on the input jack contacts.
The pedal is working quite nicely now! I just got done goofing on the live version of "Dazed And Confused" with a single slapback echo (minus the violin bow). 
I'll get a zener diode for it tomorrow, and will also get the capacitors for the high rolloff mod while I'm at it. Mabye a new input jack also.
C.K.
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 11/07/2005 : 09:13:39
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Great job 
Always good to hear about a pedal coming back from the dead. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 11/13/2005 : 18:17:53
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Finally got the DD-2 all put back together this morning, and all appears to be well with it.
Putting the guts of one of these back into the case is much more painstaking that getting them out, that's for certain. 
I replaced the input jack with one from a junked pedal that didn't look to be as corroded on the contacts, and added a .047uF capacitor across the outer lugs of the feedback control also.
C.K.
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Topic |
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An Abused DD-2 Needs Help
