Newb...R&D Compressor problems...

[parkerboy]

Anybody build the Ross Compressor from JD Sleep's site? I am having a problem that I have yet to solve. I've narrowed it down to the actual board because signal goes through with the effect off and on...only it is heavily distorted when the effect is on... :x.. I did change a few things, like using a 3PDT instead of the DPDT that is on the parts diagram.. I also added a power adapter..both of which I carefully laid out (using the diagrams on his site) and triple checked before wiring for real. Anyone have any ideas?

[R.G.]

Anyone have any ideas?

Lots of them. I typed them down in the "Guitar Effect Debugging Page" at GEOFEX. The section on new effects that have never worked is kind of aimed at this.

The usual thing to do is to measure all the DC voltages at all the active device pins and then from that figure out what's getting the right voltages and what's not. From there, the fix usually leaps out.

[parkerboy]

I actually found your debugging page just last night and started working on solving the mystery...I have found everything to be in order so far as DC voltage is concerned. Every componenet that is supposed to be getting power is, and is grounded properly. I'm hoping something will "leap out" at me soon. Will let you know when it is complete (if). Thanks a lot

[parkerboy]

I think I just figured out (using your audio probe) that the IC is shot on my compressor..I used my little brother as a signal generator..haha (he strummed the strings for me) and probed everything from the input of the board to the input of the IC with good results. Then I probed the output and all hell broke loose; it was heavily distorted and so was everything after that. So I guess I found it? By the way, this confused me: A couple of capacitors (C2, C5) and the collector of the first transistor (Q1) generated no signal when probed, but everything else in the input chain did. I dunno...the file i used is from the General Guitar Gadgets website.

[parkerboy]

I knew tyhat I had gone through all of the parts on the list included in with this build file, but the 2K TRIMPOT is listed in the description, so I missed it. Lo and behold the one I had in there was a 500K for some reason :roll: ...that   was my problem. So if anyone else builds this make sure you use a 2K trimpot and nothing else.

[Mark Hammer]

Heh....

Heh, heh, heh....

Oh yeah.....

Un-huh.......

Yep.......

NEVER, EVER happened to me.

heh, heh, heh......or anyone else here.  No sirreee.

Nope.

Heh, heh, heh...

I think you just received your club membership card in the mail. :wink:

[David]

That sounds like what happened when I breadboarded a Flatline a little while ago.  On that one, a resistor bridges a LDR to control gain on an op-amp.  The resistor wasn't hooked up correctly, so the gain was VERY high and the poor op-amp overloaded terribly.  Mark got the assist for helping with that one.  His comment was that this was a case of WTHIIDT, otherwise known as "What The Hell Is It Doing THERE?!"

Have fun with your "squeeze box", and don't be under "pressure"!

[parkerboy]

Haha. I'll have plently of fun now that I got it working...you could say my pedal was FUBAR before the incredibly simple mistake in value dawned on me.