Advice for troubleshooting a BD-2 circuit?

Started by mg.audio, September 18, 2014, 12:32:45 AM

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mg.audio

Alright, so a friend has asked me to build a clone of a blues driver with a pre/post boost stage. I studied the schematic and tried to determine which parts of the circuit are not needed since I will not be using FET switching. I drew a new schematic in my pcb design program,
(which, by the way, doesn't seem to have a FET transistor option - so I used some npn transistors in the drawing and labeled the drain, source, and gate on each transistor that should be a FET.)
So now I have the circuit on a breadboard, and of course, it doesn't work. Almost no sound at all, just a faint clean signal when all the knobs are cranked. Bear in mind I'm only testing the blues driver section right now. I need advice on how to go about troubleshooting this beast. First thing that comes to mind is open up an actual BD-2 and compare multimeter readings at various points within the circut. Is that a good way to start? Schematics:

Boss schematic:


My schematic:

duck_arse

find a fet/jfet symbol. if you have to use the bjt, most of us would have the gate terminal equivalent to the base, the drain as the collector, and the source to the emitter. most of us, but there are some strange types around.

does your R7 = 220R or 220k, as a squint at the boss shows? that'll put a crimp on your day.

comparing voltage to a working unit is an excellent way to find what the voltages should be. then you'd look to:

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

and you would have all your own answers.
don't make me draw another line.