BOSS SD-1 Mystery

[newfish]

Hi All,

I recently changed a couple of components on my SD-1.

Using the schematic below 

http://www.hobby-hour.com/electronics/s/sd1-super-overdrive.php

I changed C2 to 0.047uF (for more 'punch'), and D4 to a Ge diode to see what the difference would be.

The pedal works in bypass.

With the pedal engaged, the LED comes on, but the signal remains the same as the bypassed signal.

I've had a probe across the Op-Amp, and there is (loud!) signal on pins 5, 6 and 7 - regardless of bypass / engaged status.

The signal drops (to the point of near-silence) just after R7 (10K).
I have replaced R7, and this haas made no difference.

My initial suspicion is that something has failed with the ouptput switching (signal is always coming from Q5 (input buffer)), but accept that I may have damaged something else, despite being careful when changing components.

Any opinions would be wecome as to how to check BOSS's bypass switching.

(I shall be on GEOFX very shortly, btw...)

Cheers,

Ian.
 

[HOTTUBES]

Check all the wires from the board to the pots for an open .
Check the traces on the board where you removed the cap & diode for an open or poor solder .
What type and make of cap did you use in C2 ?

[pinkjimiphoton]

just a shot in the dark, but did ya put the diode in backwards? i did that recently, killed all the signal completely. reversing the one diode cured it.

[newfish]

Thanks Guys,

I've checked the diode, and it's in exactly the same way as the marking on the PCB.

The cap I've used for the new C2 is a poly box.
I know ther's signal going to the Op-Amp, so am fairly sure it's not this component / joint at fault.

I've also re-flowed all of the joints I've made, just in case.

No dice.

Am suspecting a duff Diode, or that I may have damaged something when de-gooping Caps C1, C2 and C3.
I reckon, if C4 had worked loose / been damaged, this would explain the lack of signal at the 'Pin 3' end of R7.

Will see what happens later this evening.

Thanks for you suggestions.

[grrrunge]

Am suspecting a duff Diode, or that I may have damaged something when de-gooping Caps C1, C2 and C3.

I recently modded my SD-1 as well. When i removed C1, C2 and C3, they were glued so hard to the board, that they broke, when i pulled them off. It may be worth it to check for broken caps here.
With the input buffer working, C1 sounds like it's non-defective, but i don't know about C2 and C3.
C2 is the coupling cap between the buffer and the drive section. Have you checked that one?

Have you checked for solder bridges around the switching FET's?

I reckon, if C4 had worked loose / been damaged, this would explain the lack of signal at the 'Pin 3' end of R7.

C4 is part of a RC network, which rolls of high frequencies after the drive section. I know from experimentation that removing C4 will just give you insane amounts of highs. If it's broken or loose in any way, my guess is that your pedal should only be very harsh sounding, not dead quiet

[newfish]

I recently modded my SD-1 as well. When i removed C1, C2 and C3, they were glued so hard to the board, that they broke, when i pulled them off. It may be worth it to check for broken caps here.
With the input buffer working, C1 sounds like it's non-defective, but i don't know about C2 and C3.
C2 is the coupling cap between the buffer and the drive section. Have you checked that one?

I replaced C3, and all is back and working.

The overall amount of gain has increased (R5 is now 100K), and I'm much happier with the overall tone of the pedal (less 'toppy' - even with the tone control adjusted).

Goop, we do not like...

Thanks for your replies, guys.