HELP troubleshooting modded BD2 Blues Driver?

matt239 · Post by **matt239** » 22 Nov 2010, 03:30

HELP troubleshooting modded BD2 Blues Driver?
OK. I was trying one more mod, & now I can't get the pedal to work. There is a little sound if drive & volume are maxed, below that, silence.
I changed C24 to 0.1uF (R34 has already been made 10k)
Changed R9 to 10k (from 6.8k)
I believe R9 is the feedback resistor on the IC op amp. (not R8, as some schems here have it..)
I have checked my joints, & re-done them. I've tried three caps @ C24, & now have original cap back in.

Can R9 not be 10k? Am I confused about what it is?
Have I cooked the IC?
Where should I start? -Any advice will be much appreciated.
Thanks.

jimbob_400 · Post by **jimbob_400** » 25 Nov 2010, 20:57

post some pictures if you can.

Check all the wires and beep them out to test for breakages. Take the opamp out and put a socket in place, try a new one.

matt239 · Post by **matt239** » 26 Nov 2010, 19:56

Thanks for your reply. I'll try to get some pics up soon. I don't have a great camera.
I'll check wire for continuity, but I don't think that's the issue. I'm pretty sure I've either overheated or shorted out either Q13 or the IC.
- I did work on it with the battery still in it...

I'll have to wait a bit for a new IC & socket. Will a J201 work for Q13 if I reverse pins 2&3? - How careful do I have to be with a JFET?
I don't have a wrist strap yet. I tried just working on it barefoot with feet on floor. I don't know if I've damaged that J201 now? - It didn't help..
What do you guys do when handling various FETs?
I've read some of the suggested general troubleshooting guidelines, I understand some of what to do, but not all of it, so I'm sorry if I'm asking dumb questions.
I need to make up an audio probe, & maybe a transistor test rig? I'm going to get a scope soon, but right now I just have a basic multimeter.
I've put the values back on the last set of mods (R9 & C24) I've done lots of other mods to it but it was still working well until this last step.

On a happier note, in the meantime I picked up DS-1 for cheap, & made some minor changes, & it sounds great!

I'm sure with a little help I'll get the BD2 back up & running..

jimbob_400 · Post by **jimbob_400** » 26 Nov 2010, 22:54

My bet would be that you've killed one or more of the FETs. Just use rubber gloves to stop any static from destroying them, you shouldn't really need to do anything else. You can also get insulating finger cots which also work. What I'd do is find a load of jfets with the same pinout as the ones currently in your bd2 and replace each one taking proper static precautions. Thing is you could have broken a few without realizing, they just may not have given up yet. I'd also use sockets on a diy fet project done at home. Just makes things easier if something does go wrong. I guess you could bend pins of the j201s and use them as a replacement, they would definitely do the job, take extra care to make sure that they can't short out if you do this!

If you're touching anything conductive with bare hands you could potentially be putting a spike of a couple of thousand volts on it. FETs dont like this...

matt239 · Post by **matt239** » 27 Nov 2010, 01:39

Rubber gloves. I like that. OK!
Sockets - definitely!
Just asked about J201s 'cause I already have some.
I probably zapped the one I tried to use.. hopefully I just need to replace Q13 with a working FET, & probably the IC. I'll begin there.
Thanks!

I'll keep you posted.

jimbob_400 · Post by **jimbob_400** » 28 Nov 2010, 01:53

good luck, hope it works out for you

matt239 · Post by **matt239** » 05 Dec 2010, 20:26

I've got the parts in & I'm going to try to repair my BD2 today, starting with Q13, then the IC. I'll report the results. Wish me luck!

Also, does anyone see any problem with these mod values?
R34 10k
C24 0.1uF
R9 10k

matt239 · Post by **matt239** » 06 Dec 2010, 07:26

Fixed it!

Thanks so much for your help jimbob_400 !

Still used J201 with pins bent (but into a socket..) A little inelegant but got it running & sounds good.
- Seems like none of the popular & widely available JFets have the same pin-out as the stock ones..
Used an LM833 for opamp, seems to work well.
I'll continue to report on my progress modding the BD2 here:
viewtopic.php?f=11&t=1062&p=124240#p124240

bobbyp · Post by **bobbyp** » 11 May 2011, 02:16

New tot he board, so If I'm chiming in the wrong place, please forgive me... I want to mod a bd-2 so I purchased one which was burnt due to someone plugging in a wrong polarity power supply. This killed the D2 and burnt the upper corner of the board so bad, I can't figure out which trances need to be repaired...
if anyone has a picture of the trace-side of a bd-2 board that woudl be great.. I just need the upper section of the board near the external power connector, and only the trace side, so just removing the back and snapping a pic is sufficient..
Thanks to all!.. killer forum.. I'm glad I joined and hope to make lots of cool things .. and therefore contribute.
-b

matt239 · Post by **matt239** » 12 May 2011, 16:17

-

viewtopic.php?f=11&t=1062&start=100

http://www.indyguitarist.com/temp1/bd2- ... on-mod.pdf

matt239 · Post by **matt239** » 12 May 2011, 17:27

Sorry they're so blurry, best I can do @ the moment..