power problem

Barcode80 · November 19, 2006, 04:20:59 PM

i have a boss bd-2 pedal. i was playing through it recently when the power to it just cut off. now, when i plug in a 9v adapter, i get nothing. when i use a battery, the LED lights (very dimly) but then fades out after about 10 secs. so basically, i have no power using a wall wart, and quickly diminishing power when using a battery. the battery has been tested and is fine. any ideas?

MartyMart · November 19, 2006, 06:10:50 PM

Sounds like an "odd" failure ! did someone plug in a reversd polarity PSU or perhaps an AC adaptor ?
Check with DMM the 9v and ground line where the initial protective diode sits and the ps cap too.
Possibly blown and hopefully, then protected the rest of the circuit !

MM.

Barcode80 · November 19, 2006, 09:10:23 PM

actually, i'm fairly new to the DMM, so i'm not suer how to check diodes.... i know how to check LEDs with it, but they just light up if they are still good. how do you tell if other diodes are good?

Barcode80 · November 19, 2006, 09:21:34 PM

okay, i figured it out, and all the diodes show an appropriate voltage drop, which i would think means they are fine?!?!? i did notice when i cracked it open that one of the ribbon cables had broken loose from one of the potentiometer boards boss uses. i replaced it with leads of my own, but is it possible that the cable had shorted something in the circuit?

Barcode80 · November 20, 2006, 01:48:51 AM

okay, i found 2 or 3 electros that were swollen, so i assume they were bad. i replaced them and still no go. ant thoughts

Paul Perry (Frostwave) · November 20, 2006, 02:34:05 AM

Might be bad news... the only way I ever got an electro to swell, (or burst) was to apply reverse voltage. If that has happened, then one or more op amps (I don't know exactly what is in your box) could have melted & is now forming a short across the power supply (hence dimness & battery flattening).

MartyMart · November 20, 2006, 03:53:28 AM

Quote from: MartyMart on November 19, 2006, 06:10:50 PM
Sounds like an "odd" failure ! did someone plug in a reversd polarity PSU or perhaps an AC adaptor ?
MM.

Sounds like that's what happened .... not good !
Get the caps changed out and check voltage of each ic pin ref - to ground.
You may have to change out the ic ....

Barcode80 · November 20, 2006, 12:18:16 PM

sweet, okay, i'll check the IC (probably socket it while i'm in there

). now i DEFINITELY am starting to wonder about the testing wall wart i use. i'll update with results...

Barcode80 · November 21, 2006, 12:07:24 AM

okay, well i checked the IC voltages on the rather odd looking M5218AL IC in the BD-2. I suspect something is wrong there, because of the eight pins, 6 are registering the exact same voltage (about 2.3 v) and one has none (grounded i assume) and one has around 4v. i know one leg of the IC should have 4 volts at it according to the schematic, but i can't find voltage references anywhere on the schem other than that. but does anyone else think these voltages seem odd?

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power problem