Questions about the SD1 mod I just performed. Please help.

[wannabweiland]

I just finished modding a Boss SD-1 to the indyguitarist SD-1 to Fulldrive specs. Here is what I did:

"Alright mod idea, here are the mouser part numbers I gleaned from other Boss mod orders:

Indyguitarist SD1 to Fulldrive 2 mod

Location --------Mod value [mouser.com part numbers]
C2 ---------------.022 uf [5989-250V.022-F]
C3--------------- .1 uf Metal Film [5989-250V.1-F]
R6---------------- 2.2K resistor [271-2.2K-RC]
C6 ----------------.022 uf [5989-250V.022-F]
C10 --------------1 uf Metal Film [5989-250V1.0-F]

D4 ------------1n34a And 1n4001 in series
D5 ------------1n4001
D6 ------------1n34a And 1n4001 in series

1n34a = germanium diode = [526-1N34A]
1n4001 = [621-1N4001]"

I also had previously done a true bypass mod with a 3PDT switch.

Here's my problem: I plugged it in and immediately, even with my amp on standby, this horrendous sound was present. Like, if you've ever been to a bar where the DJ pulled out a cord or something and it sounds like a loud buzzy hum. This was with the pedal in bypass. Turning it on intensified the sound greatly.

Any ideas on why this would happen?

Also, above it states to run the 1n34a and 1n4001 in series in D4 and D6. My understanding is that I'm supposed to solder a 1n34a to a 1n4001. Is that correct?

My sincere apologies for these possibly dumb questions. I'm new to this and I have no background with electronics. I'm decent at soldering and thought I would give this a go.

[R.G.]

Mostly likely is you broke a wire. The likeliest wire is the input jack ground wire to the circuilt board.

If not that, one of your mods is not what you think you did.

[wannabweiland]

Ok. 2 questions then:

1. What should the orientation be of the 1n34a and 1n4001 in D4 and D6? And the 1n4001 in D5? These are the only components I had any doubt about.
2. Would this noise happen if the input and output jacks were accidentally reversed? I haven't looked, I just happened to think of it this morning.

[R.G.]

1. What should the orientation be of the 1n34a and 1n4001 in D4 and D6? And the 1n4001 in D5? These are the only components I had any doubt about.
2. Would this noise happen if the input and output jacks were accidentally reversed? I haven't looked, I just happened to think of it this morning.

1. Don't know. Probably the same direction as the original diodes were. You can just refer to the digital picture you so thoughtfully took of the board before you did your mods for just such an eventuality.
2. Look.

[wannabweiland]

1. What should the orientation be of the 1n34a and 1n4001 in D4 and D6? And the 1n4001 in D5? These are the only components I had any doubt about.
2. Would this noise happen if the input and output jacks were accidentally reversed? I haven't looked, I just happened to think of it this morning.

1. Don't know. Probably the same direction as the original diodes were. You can just refer to the digital picture you so thoughtfully took of the board before you did your mods for just such an eventuality.
2. Look.

Lol I will refer to the several pictures I did in fact take. And I will indeed check the jacks. I just figured with all the experience and wisdom here somebody might actually provide some insight.

[armdnrdy]

I just figured with all the experience and wisdom here somebody might actually provide some insight.

Might actually provide some insight?

I believe with the minimal information that you provided, R.G. actually did!

The problem that you described can be one of a myriad of things.

Now let's get a bit more info:

Did this effect ever work correctly after you did the true bypass mod?

It's very strange that you are getting a hum while your amp is on standby. Something is very wrong!

[PBE6]

I modded several SD-1 and DS-1 units when I first started out. Most of them worked fine, but one SD-1 in particular broke in the strangest way and drove me absolutely bonkers trying to track down the source if the problem. Eventually out of frustration I ended up reheating all the solder joints on the board that were attached to the wires - and voila! It worked perfectly after that.

If you can't find anything obviously wrong elsewhere, try re-doing those joints. All the flipping of the board back and forth seems to do a number on those wires. And based on the buzzing sound, it's probably one of the ground wire joints that's faulty.

Good luck!

[wannabweiland]

The pedal worked flawlessly after the true bypass mod. To be honest, I haven't opened it up since my last post due to frustration.

My gut tells me it has something to do with the orientation of the germanium diodes.

[samhay]

^My gut tells me it has something to do with the orientation of the germanium diodes.

A link to a schmatic, like this would be helpful: http://www.hobby-hour.com/electronics/s/sd1-super-overdrive.php
If you put some/all of D4-D6 in backwards it will still pass signal, but the clipping will be different. If you short them, it will still 'work' but have a gain of <1.

Your description of the problem tells yout most likely what is wrong - there is a break in the ground and/or signal path.