Crybaby Schematics

[RDub]

I've got a Crybaby gcb-95. It's the Revision E board. When you activate the wah, the volume drops to almost nothing. I'm thinking it's got a bad cap,but the schematics I've found don't seem to jive with what I'm seeing on the board, and a couple of the caps don't have any writing on them. Anybody got any info??? The correct component values??? Maybe a good schematic for the Rev. E???

[Tim37]

its not what your looking for but it might help theres a lot of pics of the board so you might be able to figure it out.

http://www.stinkfoot.se/andreas/diy/mods/dunlop.htm

if that fails you can buy a upgrade board off ebay. but they are kinda pricey because you can get a complete crybaby on there for about the same price.

http://cgi.ebay.com/CryBaby-PARTS-GCB-95-F...A1%7C240%3A1318

[Paul Marossy]

I have the basic GCB-95 schematic shown here: http://www.diyguitarist.com/DIYStompboxes/WahMod1.htm

The only thing on that schematic might differ from yours is the resistor value on the emitter of second transistor.

To figure this one out, I would send it a continuous tone from an audio oscillator or similar device and then use an audio probe to follow the signal path to see where the signal is dying. Where it dies is going to be where your problem area is. It's very easy to build one, you can see how to do that here: http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf

I suggest the audio probe because it could be any number of reasons why it is behaving like that - it could be an input/output jack, the bypass switch, a bad cap, a bad transistor, a crack in the PCB somewhere (like at the input/output jacks, seen that before), something shorting to ground somehow, the wiring harness, etc., etc.

Edited April 15, 2009 by Paul Marossy

[RDub]

Thanks for the replies guys. Paul, I like the idea of that audio tester, and think I'll make one up for this job. Thanks to one of the guys at the stinkfoot site, I've found that the orange caps, labeled 224 are .22uf. Still not sure about the blue caps on my board though. He suggests they are probably.01uf. On my board, the big electrolytic cap, that seems to me to be a filter cap says 100uf@16V. All the schematics I've seen don't have this value anywhere. Think I'll pick up a couple .22 and .01, as these seem common on most schematics I've seen, and try out Paul's audio probe, and see what I get. Thanks for the help.

[Paul Marossy]

Yeah, there are (2) 0.22uF caps and (2) 0.01uF caps in the signal path, one of which is the "sweep cap". The 0.1uF cap and the 100uF caps are for power filtering when being operated on a DC wall wart power supply.

I wouldn't worry about the small differences in the power filter cap on your circuitboard vs. the schematics - they seem to always be making minor changes to some of the components. The basic wah circuit essentially remains unchanged from the original for the most part, though. They only changed what they had to in order to use more modern transistors and they added the input buffer to avoid "tone sucking" when in bypass mode.

Edited April 15, 2009 by Paul Marossy

[RDub]

Thanks Paul. I'm learning about amps and circuits and such, and figured the electrolytics were for filtering after looking at the schematic. My Rev. E board doesn't have the buffering circuit, so I'm gonna do the true bypass mod on it, if I can get it up and running. Just wasn't sure what the cap values were, so thanks for the help.

[Paul Marossy]

Thanks Paul. I'm learning about amps and circuits and such, and figured the electrolytics were for filtering after looking at the schematic. My Rev. E board doesn't have the buffering circuit, so I'm gonna do the true bypass mod on it, if I can get it up and running. Just wasn't sure what the cap values were, so thanks for the help.

It doesn't have a buffer circuit on it?

[RDub]

Nope the rev. E was the first to put the jacks on the board. I believe rev F is the first with the buffer.

[Paul Marossy]

Nope the rev. E was the first to put the jacks on the board. I believe rev F is the first with the buffer.

Huh, I didn't know that. I will file that for future reference.