HELP! with Boss pedal problem (RG, Ansil?)

[phillip]

Hi Guys, and Merry Christmas to everyone!  

I got a used SD-1 off Ebay, and it worked fine last night, but now that I've modified it to the 5-Star Ge. specs (like my other SD-1) it doesn't work in either effect mode or bypass mode, but the LED does work and the two BJTs in the switching section do flip-flop back and forth, so that means that the switch is also working.

I've checked all the wire connections, which are all good and I also looked for solder bridges and the such, but there are none.  I've checked the regular BJTs to make sure that they're all good, and all 4 tested to be.  I've also checked my solder connections on the new capacitors and they're all soldered in securely.  The JFET Q1 has infinite resistance between it Drain-Gate and Gate-Source junctions.

Now, here's the thing...the JFET Q2 has a resistance of 2M7 between the Gate-Source junction.  I know that the resistance there is supposed to be infinite.  Has this JFET gone belly up?

TIA!
Phillip

[phillip]

Nope, scratch that.  The resistance of the Gate-Source junction of Q2 on my other SD-1 measures the same...what else should I look for?

Phillip

[phillip]

Okay I think I found the problem...the 0.047uF input capacitor was measuring a resistance of 1.3 ohms...definitely needs to be replaced!

Phillip

[Joep]

Hi Phillip,

A friend on mine had some intermitted problems with his SD-1, I had a look at it and the were a lot of bad solder joints. I resoldered the whole pedal and the problem was gone.

Happy holidays,

Joep

[phillip]

Thanks Joep.  I replaced the capacitor, but it still wasn't working in either mode...in effect mode you could hear some hissing as the volume of the pedal was turned up.  I took the back plate and plastic insulating piece back off and poked around inside for a while, measuring resistors and diodes and transistors, and when I gave up after not finding anything wrong, I plugged it back in and....it was working again.  Very strange indeed.

Phillip

[mattv]

Okay I think I found the problem...the 0.047uF input capacitor was measuring a resistance of 1.3 ohms...definitely needs to be replaced!

Phillip

1.3 ohms means pretty solid continuity with my meter. That is, if I measure a plain wire's resistance, it usually says 1.2 or so ohms. I don't think that's the problem.
So it doesn't work in bypass or effect mode? Try using an audio probe to see how for the guitar signal gets. Since it was just working last night, it's probably something right under your nose.
Good luck!

[Joep]

Hi Phillip,

That looks like the same problem my friend's SD-1 had. I couldn't find the problem in the first place. It also mysteriously went from working to non-working. But after I had a better look at the solder joints, I figured out that might be the problem. If you have a real close look you might notice some tiny cracks around the part leads. Some of the are hardly visable.

Regards,

Joep