DD-20 stopped working

[Ericmc]

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!

 

[Ericmc]

Here is the backside of the top pcb:

 

[fig]

Howdy,

Here's the service manual which includes the schematic.

https://www.synthxl.com/wp-content/uploads/2018/05/Boss-dd-20-service-manual.pdf

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

There are some really sharp folks here...maybe this will assist them

 

[Bio77]

Are you using the power supply that used to work with this unit?

 

[xefned]

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.

 

[Ericmc]

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.

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

 

[spi]

Check D9 if you can find it... see if it's blown. Looks like it connects to power supply.

 

[Ericmc]

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.

 

[xefned]

Currently using a true tone cs6 to power…

You need to be using a center positive adapter for that Boss. (in case that wasn't already clear.)

 

[Ericmc]

You need to be using a center positive adapter for that Boss. (in case that wasn't already clear.)

I believe I am, unless this is the wrong adapter?

 

[xefned]

I believe I am, unless this is the wrong adapter?

OK, sorry. LOL. Didn't mean to be a pest. Just wanted to make sure you weren't missing the obvious. Carry on!!

 

[Ericmc]

OK, sorry. LOL. Didn't mean to be a pest. Just wanted to make sure you weren't missing the obvious. Carry on!!

Well actually i did mess up and use a different connector when taking the photo earlier and grabbed the wrong one, so leave it up to me haha.

 

[fig]

There are a lot of test point references...that service manual might tell you how to check it.

 

[Mcknib]

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

 

[Ericmc]

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

 

[DAJE]

I have a DD20, though I haven't used it in years. It runs off a normal center negative 9V adaptor, just like compact Boss pedals.

 

[music6000]

What type of power supply should it use? My guess he plugged the wrong kind in…

It uses Standard Boss 9vDC - Centre negative, 200ma draw!

Probably used Positive Centre?????

It's shown what polarity is on the Pedal as Mcknib has shown above!
This was pointed out by me in the Original post
It uses Standard Boss 9vDC - Centre negative, 200ma draw!:

https://forum.pedalpcb.com/threads/does-anyone-here-repair-pedals.13794/#post-156981

 

[zgrav]

so..... if the correct polarity power supply with enough current is plugged into the pedal now..... does it work?