Just finished modding my crybaby wah pedal

[moody07747]

I just finished, i got all the parts in and tested it....but it didnt work.

i would be able to play but as soon as the pedal was turned on everything went silent.

I went thought the mods and swapped out parts untill I got to the amp resistor swap mod found here

http://www.diyguitarist.com/DIYStompboxes/WahMod.htm

It just wont work with my pedal

other than that everything else works great...im still looking for that amp though as I don't like that 50% volume drop when its switched on.

Anyone have any ideas on why that would not work?

All the other mods are done and working fine and although I do hear a little difference in the pedal its not as much as I thought it would be but im still happy with it.

[tcobretti]

Do you mean specifically the 470 ohm resistor when you say "amp resistor"?  All those mods all classic crybaby mods that should work like a champ on every crybaby that I've heard of.  It sounds to me like maybe you put the wrong value reisistor in or possibly replaced the wrong one in the first place.  I'd use a multimeter to measure the resistor in the pedal and the one you wanted to replace it with and make sure you have apples and apples.

If you don't have a multimeter they are easily and cheaply had at walmart, and you will need one for this pastime.

Edited to correct my freakishly bad grammar and spelling.

[jonathan perez]

from the words of mr wampler himself, TEST THE PEDAL AFTER EVERY MOD. 

[Paul Marossy]

Are you sure that you didn't mangle one of the tracks on the PCB?

[moody07747]

Are you sure that you didn't mangle one of the tracks on the PCB?

the board is fine...ill get my meter to it now, yes i ment i am talking about that 470 Ohm resistor

" Finally, I replaced the stock 470 ohm resistor at the emitter of Q1 with a 270 ohm resistor."

meter time

[moody07747]

OK I set my meter which I got last week to 2K ohm and tested a brand new 270 ohm 1/4" resistor (Red, Black, Brown, Gold) with it.  I got a reading of .265 ohms.

I tried testing the leads of the stock resist on the board (printed in its place is "R3")
this resistor is placed between the middle lead of Q1 (marked "MPS A 18 534") and the neg. lead of C3 (a 63V 4.7uF  capacitor)
But i cant get any reading on the meter for some reason.

I'm sure i didn't burn it up...i set my soldering station to 330C when i work on boards like this one.

I'm not sure why I'm not getting a reading on it but if i have to ill get another transistor for it.....but i should not have to...this is the one that should be replace with a 270Ohm to boost the signal output.

i plugged the colors of the original resistor (R3) into this site
http://www.ealnet.com/m-eal/resistor/resistor.htm
the colors on it are Brown, Orange, Red, Silver

That's a "1300ohm" 10% Tolerance resistor from what the site says. but that cant be right as the mod site says its a 470 ohm resistor

" Finally, I replaced the stock 470 ohm resistor at the emitter of Q1 with a 270 ohm resistor. This gives the circuit a little more gain, and it also helps to increase bass response some, too. Now my volume doesn't drop off the way it did before I made these modifications."

my brains fried from lack of cheese fries from outback, ill be back later...

at this point I'm thinking of putting all the components back to stock...i didn't really notice much difference in the sound at all...i still want to swap out that 470 to amp. the circuit though

[moody07747]

I know what i dod...i put some resistors that were net to eachother in the wrong place.

does anyone here have a few close shots of their original Rev.g board that i can have to look at...i just want to put everyone back in place and start over again on it.

[tcobretti]

I don't know if this'll work or not.





You could always just compare what you have to a schematic.

[Seljer]

OK I set my meter which I got last week to 2K ohm and tested a brand new 270 ohm 1/4" resistor (Red, Black, Brown, Gold) with it.  I got a reading of .265 ohms.

err, you have it set at 2kohms, that means it gives you the results back in kohms too, so .265kohms would be 265ohms which is close enough

[moody07747]

second thoughts....the plans on this page are messing me up

I'm not sure if hes going by B, C , or E by the top of the board or following the electrical path underneath it for the placement of the new 270 ohm resistor.

Thing that's messing me up is this is the only thing that's not labeled.

another thing is he says resistor 15 (according to my board) is a 68K resistor but on my board its a 68000 ohm (Blue, Grey Orange Silver)

now i swapped the one to the right of this resistor, (the original Brown orange red silver is in there now...that's R3) but i didn't even touch resistor 15

im so mixed up right now...

to amp the output should the new 270 resistor be in the R25 or R3 spot...thats what i really need to know.

this is the current layout of the board
http://s2.photobucket.com/albums/y22/moody07747/Musical%20Instruments/Electric%20guitar/WAH%20pedal/?action=view&current=Layout.jpg&refPage=&imgAnch=imgAnch1

I swapped out resistor 1
http://s2.photobucket.com/albums/y22/moody07747/Musical%20Instruments/Electric%20guitar/WAH%20pedal/?action=view&current=R1_Changed2.jpg&refPage=&imgAnch=imgAnch2

then swapped out resistor 3 which didnt work so i put the original back in and now i cant get a reisistance reading on it for some reason
http://s2.photobucket.com/albums/y22/moody07747/Musical%20Instruments/Electric%20guitar/WAH%20pedal/?action=view&current=R1_Changed2.jpg&refPage=&imgAnch=imgAnch2

the first mod i did was swapped out resistor 5 and it worked great
http://s2.photobucket.com/albums/y22/moody07747/Musical%20Instruments/Electric%20guitar/WAH%20pedal/?action=view&current=R5_Changed2.jpg&refPage=&imgAnch=imgAnch4

2nd mod i did today was the sweep capacitor swap
http://s2.photobucket.com/albums/y22/moody07747/Musical%20Instruments/Electric%20guitar/WAH%20pedal/?action=view&current=Sweep_Cap_Changed2.jpg&refPage=&imgAnch=imgAnch5

thats a ".022MFD/ 100V RADIAL MYLAR CAPACITOR"
(allelectronics.com item# RMC-223)

So whats my next step?

[moody07747]

just giving this a small bump to the top

I have all the mods on this chip done except that amp mod with the 470 ohm to 270 ohm resistor swap amd at least its working...

putting it in the place where R3 didnt work so im going to try putting it in the spot of R15, following the wiring on the board this is inbetween the lead for Cap. 9 and the collector lead on Q1

ill report back in a minute or two with my findings.

[moody07747]

it needs a little more bass in my opinion and does not sound as good as it used to with the distortion pedal but i never really use them togeather too much...the phaser on the micro cube does good with that.

anyways i put the 270 ohm, 1/4W resistor in the R15 spot...to the left of where i had it originally and its working, i have allot more gain and no more 50% volume drop at all which is really nice.

now i feel like putting an LED to let me know if the pedal is on, like the boss DS1

anyone know of plans or have ideas for that?

i always forget to turn it off but i have the power adapter for it so batterys dont go dead.

my parts for the power supply are getting here around monday so ill update you all on that


so the outcome, on a Original Dunlop Crybaby wah pedal marked Model GCB-95 on the bottom plate and REV H on the PCB the amp mod is to replace R15 with a 270 ohm, 1/4W resistor

got that?  lol

Thanks for the help everone, im happy its working again

[tcobretti]

For future reference: 68k means 68000.  "k" is an abbreviation for kilo which is a prefix meaning 1000.  The abbreviations get far more confusing when you get into capacitors so yo may want to brush up on decimal notation. 

The most common way to put an LED in a circuit is a 3pdt switch available in the forum store.  I don't know for certain that will work in a wah pedal because the size of the switch is crucial, and I've never bought a 3pdt to know if they are the exact same size.

Good job getting it working!  Keep at it, it only gets easier.

[waldo041]

it needs a little more bass in my opinion and does not sound as good as it used to with the distortion pedal

i see you are using the original mpsa18 transistor's. try some lower gain transistor's. i used a 2n3904 in Q1 and a bc109 for q2. the 2n3904 had a hfe of 220 and the bc109 was around 320. from my efforts i found on a search in this forum that anything under 200 is no good and anything over 500 is no good. they will work, but some people can hear the difference and some cannot. try it and let us know what your ear hears. this gave me a better bass response and kept me out of radio interference with the same mods you have done. i also eliminated the input buffer circuit. if you need a buffer the output buffer circuit is a better way to go.

peace,
waldo

[moody07747]

it needs a little more bass in my opinion and does not sound as good as it used to with the distortion pedal

i see you are using the original mpsa18 transistor's. try some lower gain transistor's. i used a 2n3904 in Q1 and a bc109 for q2. the 2n3904 had a hfe of 220 and the bc109 was around 320. from my efforts i found on a search in this forum that anything under 200 is no good and anything over 500 is no good. they will work, but some people can hear the difference and some cannot. try it and let us know what your ear hears. this gave me a better bass response and kept me out of radio interference with the same mods you have done. i also eliminated the input buffer circuit. if you need a buffer the output buffer circuit is a better way to go.

peace,
waldo

Thanks for the info, i think i will mod the pedal some more.

do you have a site or any wiring sheets showing what do did??

if not, dont worry about it...i think i got this wah modding down now.

[moody07747]

looked up those parts.

mouser.com part numbers
511-2N3904
and
526-NTE123A

will work, right?

just makin sure...i hate to order then find i have a part that wont do then have to reorder...

[waldo041]

looked up those parts.

mouser.com part numbers
511-2N3904
and
526-NTE123A

will work, right?

just makin sure...i hate to order then find i have a part that wont do then have to reorder...

yes those will work. i got mine from the cave.

Bc109 work a like
http://www.smallbearelec.com/Detail.bok?no=272

2n3904
http://www.smallbearelec.com/Detail.bok?no=283


if you have the $, buy several of each. there is no telling what hfe ranges you will get. the bc109 may not fall under the 500 hfe range so maybe a bc108 may be better. i got lucky with one bc109 in the batch of 6 i got.

what you are ultimately trying to do is get the hfe in the range i stated earlier. try and find some NPN transistors that fall within the range and try different combo's. with the lower hfe going into Q1.  also buy some sockets so you can swap them out without reheating those delicate pads.
http://www.smallbearelec.com/Detail.bok?no=101

let me know how it works out.

peace,
waldo

[moody07747]

thanks for that info, i got another site here

http://www.futurlec.com/index.shtml

ill order 20 of item BC108 and 20 of 2N3904

I have a meter with a setting for HFE so i can just plug a transistotr in and see its "gain"/HFE

[moody07747]

I just recorded a sample with the DS1 and wah in line. link here

http://www.tindeck.com/audio/my/185l6

Again, this is an unmodded boss and modded crybaby

This is just to let you know how it sounds

Song order: Clean > Distortion > Clean Wah > Distorted Wah > Wah on and off > distorted/Clean wah

To me its starting to sound like its playing through a cheap set of computer speakers on the clean setting....I'm hoping swapping out those transistors will fix this some.

I should get my cousin to put up a recording with is wah so i can compare the modded and unmodded original crybaby pedals.

[moody07747]

I got my 2 transistors in today, a BC108 and a 2N3904

As I was told, I'm putting the BC108 in place of Q2 and the 2N3904 in place of Q1

In Q1 is a transistor marked:

"MPS
A 18
534"

I looked up at the data sheet page I have but could not find any info on it.
http://users.otenet.gr/~athsam/database.htm

The Q2 transistor is marked the same.

I need the data sheet to tell me the B, C, and E of these old transistors so i know how to install the new ones.



also, the 2N3904 has an hFE of 150 and the
BC108s are about 307 according to my meter.

it was also suggested that i stay between 200 and 500 was also told to try it out and so i will.

I have 20 of each transistor so ill get to testing them all and see if i cant get a higher gain one for the 2N3904

i see you are using the original mpsa18 transistor's. try some lower gain transistor's. i used a 2n3904 in Q1 and a bc109 for q2. the 2n3904 had a hfe of 220 and the bc109 was around 320. from my efforts i found on a search in this forum that anything under 200 is no good and anything over 500 is no good. they will work, but some people can hear the difference and some cannot. try it and let us know what your ear hears. this gave me a better bass response and kept me out of radio interference with the same mods you have done. i also eliminated the input buffer circuit. if you need a buffer the output buffer circuit is a better way to go.

peace,
waldo