boss dm-2

[freak scene]

i just took one of these on a trade, it sounded great.  then i noticed that the reverse polarity protection diode was blown, removed, and bypassed with a jumper wire.  seems to be a common issue with these.  anyways, it worked, then i decided to re run the blown traces, and put a new diode in (i used a 1n4001).  shazam it doesnt work anymore. 

any problems using a regular diode in lieu of the zener?  i tried putting it back to the way it was before i re ran the traces etc.., and nothing.  i also noticed the boss adapter was putting out 13 volts, is this normal?

thats what i get for trying to fix something that still worked i guess.

[Krinor]

i just took one of these on a trade, it sounded great.  then i noticed that the reverse polarity protection diode was blown, removed, and bypassed with a jumper wire.  seems to be a common issue with these.  anyways, it worked, then i decided to re run the blown traces, and put a new diode in (i used a 1n4001).  shazam it doesnt work anymore. 

any problems using a regular diode in lieu of the zener?  i tried putting it back to the way it was before i re ran the traces etc.., and nothing.  i also noticed the boss adapter was putting out 13 volts, is this normal?

thats what i get for trying to fix something that still worked i guess.

Have you tried running it from a battery, and also tested it with both PSA and ACA adapters respectively ? I'm sorry that I'm not knowledgeable enough to be of much help, but I just got one of these myself and was careful enough to read about how to properly power the thing before I plugged it in the first time. I currently bypass the PSA vs ACA adapter problem by powering the DM-2 via a BOSS NS noise suppressor (which is powered by a PSA adapter).

Check out these threads, maybe you find some interesting hints which might lead you to a solution:

http://www.bossarea.com/other/aca.asp

From what I have read elsewhere, the older ACA adapters read 9 volts but are in fact closer to 12. Check out this info:

http://www.cioks.com/faq/faq.htm#difference

And this is a quote by user "Andreas" from the Harmony Central forum:

"The old ACA pedals wants to see 12 volts DC on the adapter jack, which is why your LED won't light up properly - it isn't receiving enough voltage. But they will also work with 9 volts DC if it is part of a daisy chain where there's at least one PSA (regular 9 volt) pedal as well, and if there's a signal cable connecting it to the other pedals. The ground connection between the pedals will then cancel out the components that lower the voltage in the DM-2."

I'm sorry that I can't be of more help...

[freak scene]

no that was a bit of help, i have tried to power it up with a battery, and the same thing.  LED works, turns on and off appropriately which leads me to believe that i didnt put the diode in backwards, but nothing else.  i used the adapter that was outlined on the bottom of the pedal which was the ACA 120.

[George Giblet]

The power supply doesn't seem to be the problem now.  AFAIK, the dm-2 supposed to run from a ACA.  The fact the LED's work means a good part of the circuit is working.

I suspect you may have upset something.

If you aren't getting any signal at all in dry or effect modes check you haven't broken off any wires to the input and output sockets (for that matter any where else too).

[freak scene]

wires all seem fine.  i went through measuring votages, and the voltage seems to stop at a 100 uf 16 volt electrolytic, i replaced it with a known good one, and the voltage still doesnt pass that point.  then i checked into the switching circuit.  this is all greek to me as far as the switching circuit goes so forgive the following terrible description:  q6 and q7 seem to be working (the c1689's? with their collectors? tied directly together and to ground).  i couldntt really tell if q5 (k30A...) is working so i tried replacing it with one from a scrapped out ds-1 and it didnt work (the one in the ds-1 worked last time i used it).  i cant find voltage on any of the IC's.

i then went at it with my o scope.  it seems the signal dies at Q1 (c732) so i dunno.

[oskar]

Is this the schematic you're working from?
http://www.freeinfosociety.com/electronics/schemview.php?id=128

You really need to post voltages and describe the problem properly.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Does it bypass?
If the sound don't get pass Q1 then why do you replace Q5?!
No voltage at the 100u cap?... Is this C37 we're talking about... then surely you shouldn't be seing any voltages anywhere else in
the unit!?

q6 and q7 seem to be working...

What voltages?

the c1689's? with their collectors? tied directly together and to ground

on the schemo above they're 2sc945's   ( "Emitters" to ground... )
Hm... did I link to the right schematic? Is there another DM2...   

i cant find voltage on any of the IC's.

Good heavens!!!
Take voltage readings then at. D1, R2,  R10/R33 junction ( Vref ), D4 (zener)...
Is the battery getting warm? What voltage is the battery. Both out of and in the circuit?

ps. This circuit is a bit beyond my competence... beware!   


Oskar

[freak scene]

Is this the schematic you're working from?
http://www.freeinfosociety.com/electronics/schemview.php?id=128

You really need to post voltages and describe the problem properly.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Does it bypass?

no it doesnt bypass, but that is the schem i am working from

If the sound don't get pass Q1 then why do you replace Q5?!

because i had one of q 5, but i dont think i have a q1.  ill have to dig a bit more.

No voltage at the 100u cap?... Is this C37 we're talking about... then surely you shouldn't be seing any voltages anywhere else in
the unit!?

yes c37, and yes no voltage past this, except at q6 and q7 when the footswitch is being operated.  and then on to q5 where there is .05 ish volts, ill have to measure and write it all down again, but i think q6 and q7 were getting 9 volts when the footswitch was operated.

on the schemo above they're 2sc945's   ( "Emitters" to ground... )
Hm... did I link to the right schematic? Is there another DM2...   

im reading off of the transistors, the writing is tiny so i may have misread.  but thats what my schem says as well.

Take voltage readings then at. D1, R2,  R10/R33 junction ( Vref ), D4 (zener)...
Is the battery getting warm? What voltage is the battery. Both out of and in the circuit?

will do

ps. This circuit is a bit beyond my competence... beware!   


Oskar

obviously mine as well. 

[freak scene]

my schem has a bit more info:

[George Giblet]

It seems weird you are getting voltage across C37 but the LEDs work.  For the LEDs to work power must be getting to the board.  C37 is pretty much across the main power supply!

A possibility is there is a broken track, either on the ground or on the positive rail.

A good start would be to probe the +ve rails and see which parts have voltage and what parts don't.  The look at the PCB and see if you can find a track which connects between those areas.

[gkoerselman]

it worked, then i decided to re run the blown traces, and put a new diode in (i used a 1n4001).  shazam it doesnt work anymore.

If it was me, and it had worked before, I would assume that it was something really simple such as this that I had messed up.

[freak scene]

it worked, then i decided to re run the blown traces, and put a new diode in (i used a 1n4001).  shazam it doesnt work anymore.

If it was me, and it had worked before, I would assume that it was something really simple such as this that I had messed up.

i also assumed that, and re checked, and re ran them several times.

[freak scene]

voltages:

d1: 0
r2: 0
r10/r33: 0
ic4 pin 4: 0
d4: 9.2
battery in circuit: 9.2
battery out of circuit: 9.2
battery is not getting hot.

[George Giblet]

You need to measure all the +9V rails around the circuit:
- pin 8 of the opamp,
- the top of R10,
- +ve C37,
- collectors of the transistors Q1, Q2, Q3, Q4.

Note which places have voltage.  Follow the pcb tracks between +v rails that have voltage and +ve rails that don't, you should find a broken track somewhere.

[oskar]

...i went through measuring votages, and the voltage seems to stop at a 100 uf 16 volt electrolytic, i replaced it with a known good one, and the voltage still doesnt pass that point...

Does this mean that you do get a 9V reading from C37 (apart from around the switching logic ) or that C37 is the first instance where 9V is missing?

I found this gutshot on a japanese page.

[freak scene]

...i went through measuring votages, and the voltage seems to stop at a 100 uf 16 volt electrolytic, i replaced it with a known good one, and the voltage still doesnt pass that point...

Does this mean that you do get a 9V reading from C37 (apart from around the switching logic ) or that C37 is the first instance where 9V is missing?

I found this gutshot on a japanese page.

c37 is the first instance of no voltage, also i measured the resistor before c37 and it is getting voltage, then i measured across the resistor, and it seems to be pulling all of the voltage (voltage drop equals total voltage if that makes sense).  i pulled this resistor out of the circuit and it measures fine.

here are some gut shots of it before i got it:

[George Giblet]

> also i measured the resistor before c37 a

Do you know which resistor it is on the schematic?  (Find where it is on your board, then find the "R" designator on the overlay of the schematic you posted).

[freak scene]

r41

[George Giblet]

That voltage doesn't help as the resistor is part of the switching circuit - you need a direct +ve measurement, say where R42 and R43 connect  and there's that "+" symbol marked on the PCB.

Anyway I think I've worked out your problem:

http://www.geocities.com/george_giblet/effects/dm2_repair.jpg

You need to add two wires (in yellow) to repair the broken tracks (in cyan).

[oskar]

+1 bridge it... I would bridge all the way to C37 though. Your fix is around D3 and that's where the flip-flop gets it's voltage right now.
Via the LED.

[freak scene]

ill give it a shot and report back tonight.