First post - broken Boss SD-1 - damaged power connections? how to debug?

[overtone85]

Hi

This is my first experience repairing a pedal. i can solder and I built/modded my own plexi amp, bu I have no experience with these circuits and debugging.

A friend gave me his broken Boss SD-1 for free because it is dead. He lent it to a friend who broke the DC socket and repaired it with super glue.

I think the pedal is made in Taiwan but I don't know how to verify this. there's no label on the bottom plate so I guess it's not MIJ.
The DC plug has a label saying that it needs a PSA adapter.

The first thing I tried was installing a 9v battery, plug a jack in the input, and see if the LED lights up. Dead.
So I opened it, the badly repaired DC plug came apart cracked and I could see that there are 3 wires coming from the contacts inside the socket.

Now, I don't know if his friend resoldered these wires. I will post pictures very soon, but for now I can tell you what I see.
The blue wire is connected to the DC tip.
The red wire coming from the battery goes to the sleeve thingy of the DC plug.
The other red wire goes to another contact inside the DC plug.

I don't have the pedal here but if remember correctly, blue wire goes to terminal 6 on the board, Red wire not-from-battery goes to terminal 13 on the board. The wires didn't break off the board so if I am wrong then it's the other way around, blue 13 and red 6.

The DC socket was already hacked, and I don't know if the sleeve contact from the battery is supposed to short on the tip (blue wire) when the DC plug is not inserted.
I also do not know if this sleeve contact is supposed to short on the other red wire contact when the DC jack is inserted.

But I remembered that these pedals disable the battery somehow when the AC adapter. So I connected the red wire from battery to the blue wire. pushed the switch and the LED did not light up.

So I tried to connect the red wire from the battery to the other red wire. and when I pushed the switch this time the LED DID LIGHT UP! I thought I was done and i could temporarily test the pedal this way. So I walked away for a minute.

When I came back the battery was very hot. So. I immediately unplugged it. I knew that I was probably shorting the battery but I din;t understand why the LED did not turn on when I connected the battery wire to the blue wire.

I tried to look at the schematic. First of all I am not sure if I was looking at a MIJ pedal that runs with a AC from the plug, and i am not sure how the wires are shorted in the socket.
The socked broke a part and the contacts came loose, that's why I am not sure.

Is it possible that I fried something by hooking up the battery wrong and now I can't tell if something else is broken?

I read somewhere that the PSA pedals don;t have a certain safety diode. i can see on by board that the diode symbol is jumpered, next to the blue wire terminal.

What's the next step to take?

Thanks

R

[duck_arse]

overtone, the next step is welcome to the forum. follow that with please post a circuit diagram, and upload us some photos of the pedal, we just love looking inside people's pedals.

do you have a multimeter, cause you're going to need one.

[PubliusValerius]

Have you examined the board and offboard components without plugging in anything, just to see if you still have good solder contacts, no bridges, any blown or swollen caps, discoloration or burnout around leads and connections?

[Trackhappy]

If you were in Australia, I'd say just send it over and I'll sort it out for you. The connector will have 3 contacts, one will be the barrel, another the tip, and a third a switched connection that is disconnected by the act of inserting the plug. That is what disconnects the battery when AC is used I assume.
From there it is difficult to guess why the LED lights when the battery is obviously shorted, but there might be a resistor in there somewhere allowing enough drop to do the necessary.
Difficult without seeing the board and/or a circuit diagram, but I would guess that the +ve would go to an electrolytic cap first up to give some low impedance grunt to the circuit. That'll have a -ve symbol on it to prove which way around you need to be. Start there with no battery connected and put your multimeter on ohms across that cap. It should flick to low resistance and climb to some finite resistance of maybe 10K upwards, very much depending on the circuit. If you get like 0-100 ohms then something is shorted. Disconnect the input connector and battery to make sure they aren't part of the problem. From there it gets tough as it may have a regulator or may not and it may be a single package type or discrete. Even if you can list the numbers off the active components (eg. 7805 regulator) for us we might get a clue as to the basic design. As the Guys said above, photos and more information so we can help.
Cheers,
Glenn.

[rutabaga bob]

Welcome!

[R.G.]

Debugging: what to do when it doesn't work.