Help with BOSS BD-2

[Renegadrian]

Guys, I got problems with a boss pedal...

BD-2
I modded to h2o specs. it works so good on battery, it doesn't work with the external power supply - the led lits for a fast moment but no the effect doesn't turn on.



please help me out!!!

[Quackzed]

bad dc jack? shouldn't matter battery or dc jack ,as long as the jack is functioning properly...?

[Renegadrian]

tried to change the dc jack it's not its fault.

I don't know why but the BD-2 hasn't got the regular DC jack wiring, it has a transistor on the ext. side and some more components...btw that pedal now is working on battery only...

[duck_arse]

looking at this HUGE circuit .....

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossbd2.gif

the battery connects through the dc socket at TP1 and 2. IF you get +9V and +8V and +4V at the 3 points shown when using battery, and you don't get those voltages when using external DC, it must be either a bad adaptor, bad plug or bad socket.

measure your adaptor V at the plug, check the polarity at the plug, measure the volts inside. eliminate one by one.

check the arrowheads on that diagram.

[Renegadrian]

Yeah tried some voltage readings...you know what this pedal is f...ng insane...

thing is:
* all my wall warts, 9 or 12V, bypassed buffered sound but no effect on
still I get the correct voltages at the right points (at the dc jack, just after the transistor and at pin 1 of the ic)
12.2v-11.3v-5.7v
no LED

* almost fresh duracell (8.bv)
8.8v-8v-4v
bypassed buffered sound but no effect on - no LED

*not so fresh duracell (6v)
6v-5.2v-2.6v
it works but no LED

[duck_arse]

well, what I'm getting now is, the LED don't work, but the pedal does. so, that shifts us to the zener diode D11, I can't read, or the led itself, or its 1k2 I can't read the name of, or the wires/solder holding those bits together.

whew, that was close. I reread, now I'd be guessing something from R40 and its transistor (less likely) all the way up to the bypassing fet next to C12, Qblob. and maybe a bad something on the "check" line still, throwing that fet off-balance.

[Renegadrian]

holy spirit passed by and saved the pedal...don't ask...
I took another wall wart, with 9V on it and not 12. it works - as soon as I switch to higher voltages it behaves like I described, but now it's ok, works perfectly on 9V...

[Mark Hammer]

Let this be a lesson to all who read this thread: moving to a higher supply voltage is not always "better".  Sometimes, manufacturers deliberately design a pedal around the assumption of a 9v supply.  Ultimately, one needs to play by the rules of the circuit, as laid down by the designer.  If the circuit accommodates other possibilities, fine, but don't expect that it will always do so.

[Ben N]

Barber specifically says that his (dirt) pedals are designed to tolerate higher voltages, meaning mainly that he uses only caps with sufficient voltage ratings. Of course, no FET switching circuits there, either.