Dunlop - Cry Baby GCB-95: how to improve it for cheap

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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby rasta_maleek » 26 Oct 2011, 22:41

Thanks a lot for sharing this info, especially bajaman.
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby ppaul » 03 Jan 2012, 08:35

Hey all, new to the forum, I did the mods to my Dunlop gcb 95 wah, BUT, it wont take one of the 0.22 caps, (the one closest to the 16v 220uF on the circuit board) it howls and feedsback (in a bad way) I put the original blue cap back problem went away. I thought I had a faulty cap so I got another 1/2 dozen different ones and tried them all only to have the same problem. I ended up putting the original blue one back, problem goes away again :hmmm: :scratch: :o
Anybody else have this problem?
FWIW: I did the true bypass, changed 3 of the caps, Input resistor decreased to 47k, paralled a 3.3uf with a .068 and the 100k resistor that goes with that mod, increased the 390R to 503R (the closest I could get with the resistors I had) and backed the range of the pedal back 1 notch.
Great thread too !!!
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby B3ar » 20 Feb 2012, 16:46

I've got a stock Rev E (90-91) Crybaby that has an odd quirk compared to other versions I've seen: there is a series resistor after the inductor between it and the feedback resistor to Q1. (That's in addition to the "q" resistor in parallel to this inductor-resistor chain.) Any ideas of what this is about?
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby B3ar » 23 Feb 2012, 05:54

B3ar wrote:I've got a stock Rev E (90-91) Crybaby that has an odd quirk compared to other versions I've seen: there is a series resistor after the inductor between it and the feedback resistor to Q1. (That's in addition to the "q" resistor in parallel to this inductor-resistor chain.) Any ideas of what this is about?


Well, having gotten the board under strong light and confirming the odd values with a meter, the answer to my guestion is that the zero ohm resistor doesn't do much other than bridging two traces. :slap:
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby dragco05 » 20 Jul 2012, 16:53

Hi guys. I made some of the most typical mods to my Cry Baby, it sounds pretty good, hope you like it. Here the notes. Regards. Image
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 27 Jul 2012, 20:55

Hello everyone...
I am seeking help modding my rev c/d crybaby, and I am confused about where alot of the components on the board are located. I seem to be able to find schematics and PCB layouts for every crybaby made after mine. I have limited electronics experience but I am old hand at soldering... Im just seeking some guidance.
I have read this thread several times all the way through, and it seems the first several pages apply to me, and that Bajaman has already done to his wah what I need to do to mine... I guess Im saying is I need visual guidance.
I appreciate any help that can be provided.

Jason
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby CHEEZOR » 27 Jul 2012, 21:04

customguitars wrote:Hello everyone...
I am seeking help modding my rev c/d crybaby, and I am confused about where alot of the components on the board are located. I seem to be able to find schematics and PCB layouts for every crybaby made after mine. I have limited electronics experience but I am old hand at soldering... Im just seeking some guidance.
I have read this thread several times all the way through, and it seems the first several pages apply to me, and that Bajaman has already done to his wah what I need to do to mine... I guess Im saying is I need visual guidance.
I appreciate any help that can be provided.

Jason

Post a pic of your circuit board and let us know exactly which mods you would like to perform and we can let you know which changes need to be made.
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby B3ar » 27 Jul 2012, 22:14

customguitars wrote:Hello everyone...
I am seeking help modding my rev c/d crybaby, and I am confused about where alot of the components on the board are located. I seem to be able to find schematics and PCB layouts for every crybaby made after mine. I have limited electronics experience but I am old hand at soldering... Im just seeking some guidance.
I have read this thread several times all the way through, and it seems the first several pages apply to me, and that Bajaman has already done to his wah what I need to do to mine... I guess Im saying is I need visual guidance.
I appreciate any help that can be provided.

Jason


A rev c/d should match up well to R.G. Keen's "Technology of" Geofex schematic or to Justin Philpott's "Original Crybaby" schematic. As Cheezor said, post pics and we'll help you out in locating what's what.
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 27 Jul 2012, 22:37

I took a pic of the front and back (just in case)

Thank you very much
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 27 Jul 2012, 22:43

Sorry, and which type mod..... I just want the thing to sound.... well better if that makes sense. Not so..... woh woh sounding. Something I will enjoy putting my foot on.
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby B3ar » 28 Jul 2012, 20:28

customguitars wrote:I took a pic of the front and back (just in case)


This is an extremely lazy go -- I didn't do a full trace but just tried to sort the few spots with identical values.
Component side, with circuit part designation per the Geofex "Technology of" article at http://geofex.com/Article_Folders/wahpedl/wahped.htm

Left column:
Guessing this cap is a 4.7 uF polarized electrolytic Cbp
470 ohm Re1
22k ohm Rc1
.22 uF Cout
1k ohm Rc2
470k ohm Rb3
10k ohm Re2

Second column:
Q1 top, Q2 bottom. Can't see the transistor markings. Might be a Dunlop house labeled component. My F has 2N3904's.

Third column:
82k ohm Rb2
.01 uF Cin
470k ohm Rb1
1.5k ohm Rfb
68k ohm Input resistor / Rin
.22 uF Cef
.01 uF Cf

Fourth column:
Inductor. 500-660 milihenry range is typical.

Fifth column:
33k ohm Rq
1.5k ohm [Not on Geofex -- power component]
Electro Cap [Not on Geofex -- power component] (100uF if like my F)
Diode [Not on Geofex -- power component]
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby Bside2234 » 29 Jul 2012, 00:06

You can save yourself a lot of time by looking at the Vox V847 layout!!!!

Edit: Here. Save you even more time:
Rev C Labeledsm.jpg
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 29 Jul 2012, 07:32

B3ar & Bside2234.... I very much appreciate the help you have given me. I waited for days before I posted this question for fear of sounding like an idiot.

I hope one day I can be as helpful as to this board as you two have been for me.

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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 01 Aug 2012, 17:57

Another quick question, What is the difference between an ICAR pot and a Non-ICAR pot??
I am trying to decide which on to use and the benifits of said pot.
AND I am starting my mods today... I'll post more as it goes.

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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby CHEEZOR » 01 Aug 2012, 18:28

Standard Wah Pot vs ICAR demo:

Link


Here is a tip from diystompboxes:
Geoffrey Teese said, that you can replace the 0,22uF capacitor feeding the middle lug (I think) of the potentiometer with a 0,33uF cap and get almost the same feel as with a ICAR-taper. Just a tip!
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby customguitars » 01 Aug 2012, 22:12

Hello again...
First off.... Cheezor... THANK YOU!!!! That video link was HUGE help :thumbsup

Here is what I have done and plan to do on my GCB-95 Rev. C...
I swapped:
Rin from 68K to 47K
Rfb from 1.5K to 2.2K
Cf from .01uf to .022uf (but plan to play with this to get my sweeping sound right
Cef/Cuf/Cin - Upgraded from ceramic to poly film caps

The Rfb & Cf mods were something I saw that Rich Morey did in his mod on the 22frets.com site...
http://www.22frets.com/tag/diwah/
And I liked the sound so I figured why not try it.

Whats next for me....
I plan on changing Cbp 4.7uf and Rq 33K to Bajaman's recomendation
AND I have an ICAR pot, 3pdt switch, and Whipple Inductor in the mail heading this way now.

If anyone has any feedback I would love to hear it, and once again, thank you all for helping me with this project!

Jason
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby biliousfrog » 31 Aug 2012, 14:44

Hi clever folks,

I've been scratching my head about this for ages and finally got the courage to sign up and ask.

I modded my GCB-95 (bought for this purpose) with the step-by-step guide that Stinkfoot created here: http://stinkfoot.se/archives/557

I've got true bypass, LED and internal trimpots for Q and gain. It sounds great but it has a major flaw...when I first press it 'ON' I get a very loud POP!

I've read that this is caused by electrical build-up and can be easily rectified by using a 1M pull-down resistor on the input, great!...My question is, "how?" Would anyone be kind enough to provide me with details on where I put the resistor? I've contacted Stinkfoot a couple of times but with no response.

I believe that my PCB is rev. I

I've built a few pedals from kits, changed my amps FX loop from parallel to serial and managed all the wah mods but, despite being great at following instructions, I'm not too clever with electronics :oops:

Any help is greatly appreciated :)
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby biliousfrog » 31 Aug 2012, 18:55

I've found a post on these boards regarding the same issue, different pedal - The solution was to put a 1M resistor from the circuit input lug of the switch to ground. It was also suggested to put another resistor from the circuit output to ground too...does this sound correct? I'll pick it up from the rehearsal room tomorrow and give it a try.
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby B3ar » 31 Aug 2012, 22:46

biliousfrog wrote:I've found a post on these boards regarding the same issue, different pedal - The solution was to put a 1M resistor from the circuit input lug of the switch to ground. It was also suggested to put another resistor from the circuit output to ground too...does this sound correct? I'll pick it up from the rehearsal room tomorrow and give it a try.


Pull-down resistors are usually enough to kill popping problems with bypassing. R.G. Keen has a more in depth explanation here: http://geofex.com/Article_Folders/box_pop.htm
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Re: Dunlop - Cry Baby GCB-95: how to improve it for cheap

Postby biliousfrog » 02 Sep 2012, 09:19

OK, done :)

It seems like it's worked but it's difficult to tell without sticking it through my rig and letting the 'pop' build up. I'll report back if there's any problems. :thumbsup
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