BD-2, save my sanity

[Barcode80]

okay, some of you are familiar with my 2 boss pedals i bought from a fellow forumite to refurbish. i got the sd-1 working, although not sounding the way i want, but working. i can tweak sound, so that is fine.

but my bd-2 is having some issues. when i power on the effect, it immediately starts crackling like there is a ground issue. this only happens with the circuit on though, so i don't think it would be grounding. then as i have it on a few seconds, it eventually starts fizzling out like a capacitor is discharging. could this possibly be a cap going bad or a cap touching ground somewhere? if it were a cap grounding and discharging, wouldn't it do it all the time, or would it maybe be a cap in the distortion part of the circuit and therefore the signal is not routed through it when bypassed and no crackle is heard?

HELP!



Thanks, by the way, to everyone that puts up with me. I'm coming along, but I am still very green...

[DrThousand]

2 ways to go here:

1)     Go ahead & warm it up 'till the noise stops.  Then CAREFULLY use freez spray.  Cool off 1 part at a time until you get the one that starts the noise...I think you know what to do next.
This technique is good on lotsa stuff & you don't need to have the schematic nearby, or even be able to read one. As a general rule whatever makes the problem get better or worse when it's sprayed is suspect & should be replaced.
Drawback: You need the freez spray; don't worry, Radio Shack will be glad to sell you some.

2)     Use good ol' circuit tracing.  Get a 1-10 ufd or cap at a voltage rating higher than the supply voltage.  Ground one lead of the cap (Usually negative) & short the output.  Obviously that should stop all sound from the box.  This was just a test of technique.
Go back one stage & short that stage output.  If the bad stuff stops, you've just passed over the bad stage; test everything in that stage: trust no-one.
Another good general troubleshooting technique.  The idea is older than I am-It's from the vacuum tube ages.
Drawback:You need some kind of information about the circuit. The full schematic would be best but if you know the pin-outs of all the ICs you may be able to stumble about enuff to get by. (If you have to do that, why not just draw yourself the schematic from the device.  Then you'll always have in case you want to build one for your new girlfriend.
Another problem is your test cap.  Ir may cause instability or not completely short the signal.

Troubleshooting is good for the brain---until it causes burnout!!!

Good Luck !

[Barcode80]

i'll try the freeze spray technique. i did notice some lightly lifted (though still solidly soldered) traces in the diode clipping section. i have the schem and i also have a pnp transfer of the board waiting. worse comes to worst, i'll etch a new board, duplicate part values and just mount the new board into the enclosure.

i'll post results.

[MartyMart]

Boss PCB pads can lift quite easily ( buggered one of mine a while ago ) so I'm not
surprized at the problems it may be causing.
You can repair it with a very small drill bit and some component leads, cut from
resistors etc.
I did that on a vintage P90 which was coming to pieces, done carefully that may help !

MM

[Barcode80]

i dunno, i tried that with the sd-1, but obviously got much better results with re-etching