Man, fixing a DD6 is a PITA

[irishstu]

A friend of mine asked if I would mind looking at his broken BOSS DD6. When an AC adapter is plugged in, the LED comes on and never goes off, no matter how many times you hit the switch. Also, there's no guitar sound going through. It's out of warranty, so I told him I would try to fix it as long as he realised it was already dead and I might make it unfixable. He agreed.

Here's a photo of the part of the circuit board that has a problem. See IC6 and Q15? Well, they're burnt out. They're part of the voltage regulation section of the circuit, btw.

Firstly, it was extremely difficult to find out anything about the circuit used. I've yet to find a schematic of a DD6 posted ANYWHERE on the internet. I DID manage to find some information on the Bossarea forums, which was enough to (hopefully) correctly identify the two components that need replacing, namely a Seiko S-8520E33MC-BJS (IC6) and a 78L05 (Q15).

IC6 had to be ordered specially and I was lucky to only have to buy a minimum of 5. Q15 was easy enough to source, once I knew what it was.

Anyway, the BIG problem was the size of these things. Q15 was bad enough, but IC6? My word, that thing is TINY. Here's a picture of it next to a standard pick.

Just to emphasise my point here, here's that photo again... more or less actual size.

Now here's a photo with the parts replaced. I know it looks messy, but it's a good clean connection ( I checked through a magnifying glass).

So after I (finally) got the parts on there, I plugged it all in and crossed my fingers, and....




IT STILL DOESN'T WORK!!!!

 

[Mark Wein]

Yeowtch. I don't know where to start in trying to fix something like that.

After pulling my Arion chorus apart I'm a little nervous about trying to replace parts on a PCB so crowded with a million little components.

 

[irishstu]

Yeowtch. I don't know where to start in trying to fix something like that.

After pulling my Arion chorus apart I'm a little nervous about trying to replace parts on a PCB so crowded with a million little components.

Yeah, you know this one is definitely a bit of a stretch for me too. That said, this is for a good friend, and he understands I may well feck it up, so it's a pretty good pedal to try to learn from. I haven't given up yet! You may notice the big rectangular diode (D3) got removed and replaced after I tested it (it seems to be fine). I'm sure I just need to find another component or two that's dodgy and it'll work.

If anyone has any ideas, I'm all ears.

 

[Mark Wein]

Yeah, you know this one is definitely a bit of a stretch for me too. That said, this is for a good friend, and he understands I may well feck it up, so it's a pretty good pedal to try to learn from. I haven't given up yet! You may notice the big rectangular diode (D3) got removed and replaced after I tested it (it seems to be fine). I'm sure I just need to find another component or two that's dodgy and it'll work.

If anyone has any ideas, I'm all ears.

Man, I wouldn't even know where to start...

 

[lancemitrex]

Just a observation. I think that Q15 should not be a 78L05. It is probably a NPN transistor in a SOT-89 package.
The 78L05 in a SOT-89 package has the center lead as the GROUND PIN. So, in the picture, above the external power is input through L3 to the top of the Diode, D3. If the polarity is reversed, then D3 conducts for a little while, hopefully shorting and blowing (up) the offending power adapter. Instead, little D3 lasts for a little while then burns up and the voltage regulator, IC6 and pass transistor, Q15 are burned up due to reverse polarity being applied. If the correct polarity is applied, then +9V would be measured at
the top of D3 (in the picture), the top of D3 is connected to the center pin of Q15. If Q15 is a 78L05, then the +9V is shorted to ground and nothing would happen except that the magic smoke might be left out of a few more components.....

 

[Modern Saint]

The 78L05 is a 5 volt regulator. Probably driving the delay chips.

Would need to look up what IC 6 does. I would suspect that you have some bad electrolytic caps as well

 

[lancemitrex]

Yes. 78L05 is a 5V voltage regulator. IC6 Seiko S-8520E33MC-BJS, is also a voltage regulator. I'll need to look up a npn transistor in a SOT89 package that has the collector
as the middle pin, base on the left and emitter on the right. You might try removing the 78L05 and measuring the voltage at the left solder pad of Q15. If that's about 5V then
take a small jumper wire and connect it from the left pad of Q15 to the right pad of Q15. Q# is typically used to specify a transistor. IC's are specified as IC# or U#.

also, the center pin of a 78L05 is a ground pin. It looks like the center pin of Q15 isn't grounded, so the input voltage isn't shorted. So, the center pin will measure about +9V, or equivalent to the DC adapter voltage.
Actually, the datasheet for the switching regulator IC6 specifies that the pass element (transistor) is to be a PNP transistor or a P-Channel Mosfet. If it's a PNP transistor then a resistor and a capacitor are required to be inserted into the circuit. The resistor and capacitor aren't present. So. Q15 needs to be a P-Channel Mosfet.
I have a part number in mind. I'll look at digikey to see how much $$.

Hope this gives you a few ideas.

 

[BoomBoomBigelow]

Jeez, lance, you sure know your EE shit, welcome aboard! Although there's only a few guys on here that have a clue as to what you speaketh of, stick around. Hope you have a warped sense of humor, and a fondness for spicy food. If so, you may enjoy it! Feel free to post a "Hi, I'm a newb" thread in The Lounge.

 

[irishstu]

Jeez, lance, you sure know your EE shit, welcome aboard! Although there's only a few guys on here that have a clue as to what you speaketh of, stick around. Hope you have a warped sense of humor, and a fondness for spicy food. If so, you may enjoy it! Feel free to post a "Hi, I'm a newb" thread in The Lounge.

No kidding. Welcome, lance.

Unfortunately I was working on this over two years ago, and I gave it back to the owner, unfixed, not long after the opening post. I'm sure I'll have more questions in future that I'll be bending your ear over, however.

 

[lancemitrex]

Yup. I figured it was long gone. One way or the other. Ha. So, I looked up some P-channel Mosfets on digikey. Just in case that DD-6 pops up or another one pops up that's been hooked up backwards.
I'm fairly certain that Q15 ought to be a P-Channel mosfet as a Pass transistor for the switching regulator, IC6. The switching regulator can source about 50mA and the current draw spec for the DD-6 is
about 65mA. The P-channel mosfet that might work is BSS192PL6327INCT-ND and they're about 71¢ each. This part has a pinout that I would expect in connecting it to the switching regulator, IC6.
Thanks for putting the pics up, irishstu!

 

[Mark Wein]

Yup. I figured it was long gone. One way or the other. Ha. So, I looked up some P-channel Mosfets on digikey. Just in case that DD-6 pops up or another one pops up that's been hooked up backwards.
I'm fairly certain that Q15 ought to be a P-Channel mosfet as a Pass transistor for the switching regulator, IC6. The switching regulator can source about 50mA and the current draw spec for the DD-6 is
about 65mA. The P-channel mosfet that might work is BSS192PL6327INCT-ND and they're about 71¢ each. This part has a pinout that I would expect in connecting it to the switching regulator, IC6.
Thanks for putting the pics up, irishstu!

Welcome to the forum!

 

[beelzebum]

I know this thread is old, but just in case someone has a similar problem, IC6 is an S-8520E33MC-BJS-T2, and Q15 is an 2SJ190. You can still find replacements for IC6 around, but Q15 is no longer made or available, and its closest replacement 2SJ278 is also hard to find. There is a company out of China that sells them both, and as of this post they sell them on ebay as well. I just repaired a DD-6 with the same issue. The S-8520F33MC was $3.00 and the 2SJ278 was $2.00 and the shipping charges were reasonable as well.

 

[Mark Wein]

I know this thread is old, but just in case someone has a similar problem, IC6 is an S-8520E33MC-BJS-T2, and Q15 is an 2SJ190. You can still find replacements for IC6 around, but Q15 is no longer made or available, and its closest replacement 2SJ278 is also hard to find. There is a company out of China that sells them both, and as of this post they sell them on ebay as well. I just repaired a DD-6 with the same issue. The S-8520F33MC was $3.00 and the 2SJ278 was $2.00 and the shipping charges were reasonable as well.

Welcome to the forum and thanks for the info!

 

[irishstu]

I know this thread is old, but just in case someone has a similar problem, IC6 is an S-8520E33MC-BJS-T2, and Q15 is an 2SJ190. You can still find replacements for IC6 around, but Q15 is no longer made or available, and its closest replacement 2SJ278 is also hard to find. There is a company out of China that sells them both, and as of this post they sell them on ebay as well. I just repaired a DD-6 with the same issue. The S-8520F33MC was $3.00 and the 2SJ278 was $2.00 and the shipping charges were reasonable as well.

Hey man, thanks for posting. So I got IC6 right?

How much did you enjoy having to resolder those parts on? I nearly went blind doing it.

If I see that guy around, I might ask if he still has the pedal. I was pretty burnt out by the time I gave it back to him, but I think I could maybe handle trying one more time. I've a feeling I might've tried replacing a couple of diodes after the initial repair didn't work. i hope I didn't screw up anything else.

 

[beelzebum]

IC6 was actually easier to solder back on. Q15 was the hard one. I had switched to using RoHS compliant solder for many jobs, but the melting temp is to high to solder that component on easily. The soldering angle, and the fact that pin 2/4 is a heat sink made that component especially difficult without the use of a proper soldering bench. I ended up going back to 63/37 for this component. If I had to do it again I would probably order some lower temp solder, or buy a ThermoJet and just use some solder paste.

 

[aliensporebomb]

How do you destroy a Boss pedal? They're indestructible. But if it's one of the chips I bet it got too much voltage. Good luck, those parts are so small I can hardly see them much less work on them.

 

[Ocolo]

hello guys!!
I m from Ukraine.
I ve got the same problem, the IC6 burned out with all the contact squaers.
Can sombody help me.
I found the S-8520E33MC-BJS-T2 detail, but i don t know where the contacts go.
and there is no schematic in the internet.
I d like to believe that somebody who have the same pedal may do a continuity test. ring-out and tell where which contact goes.
Thanks a lot for paying attention!! ))

 

[Sam Lloyd]

Hi there, new member here, first post. I joined because I have two DD-6 pedals that are exhibiting the same kind of nonsense, and so far I haven't had any luck getting either to work. Just checking to see if anyone might have stumbled upon the schematic or service notes for the DD-6? I found the ones for the DD-7, but there are significant differences so that was of little help.

BTW, on one of the pedals I get no clock or serial data output from the A/D chip until I feed the board 3.3V from a bench supply. (with U6 and Q15 removed) Mine had a MAX6322 uP supervisory chip installed in the U6 location when I got it, so I replaced it with the same chip and it just started overheating. After reading this post I'm wondering if someone might have installed the wrong chip in a misguided effort to repair this thing.

Anyway, TIA for any help, insight, schematics, etc!