DD-20 stopped working

E

Ericmc

Member
So I have a DD-20 that I put on a shelf a while back. I sold it after a while (didn’t test it before I sold it) and when the guy got it he said it wasn’t working. It is possible that he powered it incorrectly, but I can’t say for sure. Now all it does is have the power led light up dimly, and that’s it. Here are some gutshots. Hoping some of the smart people here can spot the issue! E7F71D0B-AA12-4492-88BE-11EF9F2F3DF1.jpeg 4162F479-E747-4F41-BF7D-13ACCF71BA21.jpeg 2EAD9CDF-5C62-4013-A86E-8F7F60191A01.jpeg
 
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Howdy,

Here's the service manual which includes the schematic.


Here is what appears to be the polarity protection diode and the LED.

oEINNEt.jpg


There are some really sharp folks here...maybe this will assist them (y)
 
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Polarity reversal is probably the problem.

In fact, it might still work properly if you plug in a CENTER POSITIVE standard BOSS DC Jack.
You mentioned your buyer already had a pedalboard set up—most likely wired for the more common center negative standard.

BOSS, smart mofos that they are, probably put in a reverse protection diode, as His Royal Figness points out. Can you find the original BOSS adapter?

i.e. it might be working just fine with the correct power adapter. :)
 
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xefned said:
Polarity reversal is probably the problem.

In fact, it might still work properly if you plug in a CENTER POSITIVE standard BOSS DC Jack.
You mentioned your buyer already had a pedalboard set up—most likely wired for the more common center negative standard.

BOSS, smart mofos that they are, probably put in a reverse protection diode, as His Royal Figness points out. Can you find the original BOSS adapter?

i.e. it might be working just fine with the correct power adapter. :)
Click to expand...
I can’t say I even remember what power supply I was using when it was working. Currently using a true tone cs6 to power of. I don’t think I even had the original boss power supply as I got it used unfortunately. Let me check and make sure I’m using the right cable with the cs6. Thanks for the help! I will report back
 
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F1BF192C-A880-4001-A342-E0FF37143C4B.jpeg

There is a picture of d9 (just to the left of the electro cap). I don’t think it’s blown? Not sure if it would be obvious or not? I am using the correct power supply but thinking back I am almost positive that guy was probably using the wrong polarity so I’m assuming that is likely the issue.
 
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The link @fig gave shows centre negative

I think maybe everybody means the buyer put a centre positive in? Just check the symbol yours has on it to make sure

Although you can't really check diodes in circuit you can still check D9 conducts around 0.6vish if it's silicon or 0.2vish shottky forward voltage and infinite in reverse using your meter diode test

20221011_195418_copy_540x540.jpg
 
Last edited:
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So I am new to this and really wouldn’t even know where to start testing it. I originally asked in another section if someone here repairs pedals because I think someone with experience would be much more likely to fix it rather than make it worse haha
 
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