Crybaby mods (Catmandue's requested)

[ivan H]

Ok, as the title indicates, this thread came about as a result of Catmandue's request for recommended mods for his JH-1 crybaby. I figure others might also like to know so here goes. I'll put up a couple of pics of my much modified ZW-45 (Zakk Wylde) that started life having the exact same circuit as the JH-1. (marketing, sheesh).
A quick note to Catmandue, notice the two transistors are oriented at an angle to the outline shown on the board. This is because the MPS-A18 transistors have a EBC pinout while the 2N2924 & 2N2925 have a ECB pinout, so must be rotated to put the pins in the right holes.
Ok, the original wah's had no buffer on the input (it'd be better placed on the output anyway) & we all know about wahs tone sucking when in the signal chain but not in use, so to fix both these things I remove the buffer & true bypass it to start with. An instruction for this is at
http://stinkfoot.se/archive/546
Edit: I just noticed that the link takes you to a German page. Under "tags" at the bottom of the page, click on CRYBABY & it will take you to all pages mentioned. You need "True bypassing the GCB-95 Wah".
Catmandue will need to follow Step 2: Mods to the pcb (rev F, G, H & I) for the buffer removal. True bypassing is covered further down the page.
Ok, after this, the "best" mod I've done is to replace the MPS-A18 transistors, which are much higher gain than those originally used, with the types called for in the original Vox patent. This calls for Q1 to be a 2N3900A or 2N2925 & Q2 to be a 2N2924 or 2N2925. Shoot for a minimum hfe of 200 for Q1 & around 400 for Q2. Doing this really brought at the best in mine, far better than other mods. Speaking of which, most stompbox forums have various threads recommending changes to 3 resistors. I think the best approach is to replace them with trimpots so they can be dialled in to your personal preference, as outlined at (The Stinkfoot Wah Mod at "Crybaby" page).
http://stinkfoot.se/archive/557
The values he recommends as a starting point aren't too far from what I ended up using.
Ok, the 2nd best mod I've done was to place a 1k trimpot in series with the inductor to make the Q of the wah adjustable, (lets you dial the actual "waah" in). Looking at the above pic inside mine, it is the trimpot to the upper right that has a "Q" written under it with a sharpie on the board. To fit the trimpot you need to remove a "link" from that position on the board. It looks like a resistor with a tan body & one black band around its center. Here is a pic with the trimpot pointed out
The trimpot's leg, or pin at the lower right in the pic has been removed (cut off) to leave only the two pins needed so that as the trimpot is turned "up" its resistance value increases (use multimeter to determine). The two remaining legs are soldered into place where the link was removed. You could use a 1k linear pot through the sidewall of the wah housing, like is done on the Multi Wah, but I don't see the need. Dial it in once & leave it. That should cover it I think. For troubleshooting, should you need to (FAQ at "Crybaby" page)
http://stinkfoot.se/archive/1358
A good read on how a wah works is at
Geo-F/X
At the upper left of the page click on "FX Technology, the technology of", then "The Technology of the Wah". R G Keen has done a lot for FX diy'ers & really knows his stuff.
While I think of it, I don't know how Dunlop came up with the Hendrix wah, but from the horses mouth, tech Dave Weyer (west coast organ & amp), who I think did more modding of Hendrix' gear than Roger Mayer ever did, tells us what mods he did to Jimi's wahs. He tells us he used a 2N3900A for Q1 (stock part) & a 2N3391A for Q2 & would sometimes increase the inductance of the inductor. If anyone has anything to add, feel free. Happy modding. Sorry for the Stinkfoot link screw ups. Cheers

 

[eSGEe]

is all that even in English????? ---er how the.....what the........where? I uhm.........

you da man

 

[JohnnyGoo]

Was gonna say i dont have a clue on about most of that but i enjoy reading it lol.

 

[syscokid]

Bummer... my trusty semi-old digital multimetter, which about 10years ago I paid about $50, doesn't have the capabilities to test transistors and the hFE's.

 

[Catmandue]

Thanks Ivan I've been busy as all get go! You know I love ya! You the man! You helped me to cherry out my Crybaby GCB-95. I will further study the Stinkfoot links you have mentioned also. I'll try copying what you wrote and taking notes of the pictures and such. This one will entail a bit more it appears to do but, I'm sure I'll have a blast as I'm doing it. Thanks again Ivan. I may have a few questions along the way. This summer I got the blessing of some work coming at me. I was able to do a trade show job this last week which I put in 62.5 hours in. It was a pretty high pace event. I have a load out for next Wednesday and Thursday. I was told by one of the top honchos at another company that I do shows for also, that he has a big show for me coming up. The bigger the show the more chance I have of getting on board. He told me I'm getting in on this one. It has been somewhat of a crazy year for me so far. Playing music, reading and modding pedals helps my mind to stay focused and satisfied. I was wondering if they sell the plastic gear deal with the teeth. This one seems like it does not go up as high as my GCB-95 or my CAE MC404 wah.

 

[ivan H]

Make sure that the pot isn't running out of rotation & thus limiting the treadle's travel. It can destroy the pot. Its easy to lift the rack away from the pinion gear & rotate it a little to remedy if it is, just loosen the screw holding the nylon loop that tensions the rack & move the loop to one side. Both the rack & the pinion gear (to suit both plain & knurled pot shafts) are available from smallbear electronics. Cheers

 

[Catmandue]

I plan on using the resistors Dave Weyer suggests. I will also do the Q adjust mod, by putting a 1 K ohm trimpot on the tan resistor looking component with the stripe. ( Worked great on the first mod you helped me with ). How do I measure the inductance on the inductor? Does it need a load on it with a battery or with a class two transformer ( power supply )? How do I measure hfe and what does is hfe?

 

[Catmandue]

Make sure that the pot isn't running out of rotation & thus limiting the treadle's travel. It can destroy the pot. Its easy to lift the rack away from the pinion gear & rotate it a little to remedy if it is, just loosen the screw holding the nylon loop that tensions the rack & move the loop to one side. Both the rack & the pinion gear (to suit both plain & knurled pot shafts) are available from smallbear electronics. Cheers

I did the loosen the screw and move the loop since I first got it. I want to get the resistors and trannys from smallbear ( are they here in the states?) I still need some more reading from the links you posted. Does it get crazy adjusting all four trimpots? I would not mind just adjusting to the settings you said were not far off from your settings? Also how crazy would it be to put in a yellow Fasel instead of a red? I like them both. I have the JH-1 ( First model ) I put a yellow Fasel also in the first mod you helped me with. The red sounds really good with certain pedals like for example the Velvet Fuzz sounds real strong, clean and with character. By the way, my circuit board is a "G" version. How do I increase the inductance of the inductor? Is it done by changing a component or by using another trimpot? I want to have all my parts and info down before I jump on doing this project. I got a feeling this pedal might turn out pretty cherry when I get grip on what I'm doing with it. I did locate some of the 1 K trimpots. I think I would prefer to use those over the precision 28 trim pot I used on the GCB-95.

 

[ivan H]

Hi Catmandue, yes, smallbear electronics is in the US & still has the transistors. There is no reason you cant use a yellow fasel. Adjusting the trimpots isn't too bad, but 2 of them are kind of interactive. It tells you on the stinkfoot site which ones. Ok, to read the inductance of the inductor it must be removed from the board & measured with a multimeter that has an inductance scale, denoted by an "L or Lx". I wouldn't try increasing the inductance of a fasel type inductor, probably destroy it. Dave Weyer had a very good relationship with Vox so could ask them for inductors of a higher value. This type inductor though, you could
Here is what one looks like un assembled & unwound minus the nylon nut & bolt of course.
Smallbear sells these parts as a kit, also a spool of #38 enamelled wire so that you can wind your own inductor. The instruction to do so are linked to the ferrite pot core & bobbin on his site, under wah parts, inductors. The kit is the last item on the inductor page. Click on "description" & the instructions are linked there. Basically, you wind 550 turns of #38 enamelled wire onto the bobbin which results in a higher inductance than needed & adjust it down by (A) removing turns of wire & (B) removing a very small amount of ferrite material from the center post of one of the pot core halves (the two center post's have an "air gap" between them.) I've wound small transformers on these type pot cores, its not too hard if care is taken. Ok, I need another coffee. Cheers
Edit; smallbear also sells these type inductors already wound. The inductance could be increased by getting a small ferrite "slug" that screws down into the hole in the center to decrease the air gap, thus it can be adjusted, though I'm not sure where to get. Cheers

 

[Catmandue]

Way cool Ivan! I'm up in the air about using a red or yellow Fasel. I do want to get the waa-h tone dialed in like "White Room" or "Tales of Brave Ulylsses" type tone. The Hendrix tone is grand by me also but, I find even with the decent stock Crybaby, along with a good OD or Fuzz it comes somewhat closer. I still need to do some reading, ordering and I seem to have more work pouring in this month on me. I could use the dough with some expenses I've had in the home and other domestic type stuff. I want to do this project right. One of the first things I plan on doing is getting the trannys, inductor and then reading over the links several times. I also want to make some notes. I tend to remember better and have more confidence when I do it this way. Like I posted earlier this one entails a bit more work and coordination. I enjoy soldering and desoldering and doing this is a heck of a lot easier than say working on cars. ( Less expensive also ). I may not want to increase the inductance it seems like it might go south on me. Maybe on the next mod I'll get brave enough to increase inductance.

 

[Catmandue]

Ivan, I try only to do two cups of coffee in the morning. ( Sometimes I grab a third on the road on the way to work ) It makes me come back to life. When I get to work I then have to hit the John to go pee after I sign in.

 

[ivan H]

Ha, yeah I have the same problem. I only drink coffee in the mornings though. The yellow fasel is more to the original wah tone I believe, the red more modern. R G Keen did research into why the old ferrite pot core inductors sound the way they do, its in the "technology of the wah" article on the GEOFX site. IIRC, its got something to do with the grade of ferrite used. DC current flowing through the inductor over the years results in a slight magnetism of the (low grade) ferrite material. Good bit of research. The effect of increasing the inductance can be simulated by adjusting the value of the 4.7uf cap. I think Analogman posted the formula for working out the value on a stompbox forum but I'll have to search for it. Ok, better have this 2nd coffee. Cheers

 

[Catmandue]

Ivan I have some questions and a comment. I'll make the comment first.

Ironically enough, I have a four digital multimeters. One Klein auto ranging, one old school Ideal and two cheapie Centecs. The ironic part is the Centecs have built in hfe checking capabilities. They show on them E NPN and E PNP. The E NPN side shows C B E and the PNP shows E B C.

This is for checking henrys? or hfe?
I want 2N3900A for Q 1 is this NPN or PNP?
I want 2N3391A for Q 2 is this NPN or PNP?
What are the transistors in the JH-1 now I notice they are MPS-A18 NPN or PNP? One looks like a MPS-A13 also?

On the one with the sharpie I was going to put a 1 K ohm trimpot.

Do you want me to post a photo of my circuit board on the JH-1? It is one of the tan boards with more stuff on it than the green one you posted. I have the green one on my GCB-95 you helped me cherry out.

Later on tonight I want to test some old transistors I have to solder suck out first from an old apprentice project I still have. I already have cannibalized a socket from it for my Rat2 over a year ago. I appreciate the assistance. Let me know if it appears I'm mistaken with my judgement here. Sorry if I'm driving you crazy with all these questions.

 

[ivan H]

Hi C man, your cool, not driving me crazy at all. Ok, the meters transistor tester (NPN, PNP) measures hfe. Both the 2N3900A & 2N3391A are NPN types (as is the MPSA18's). The 2N3900A is a "low noise" transistor. The MPSA13 is part of the input buffer circuit. The MPSA13 is an NPN Darlington transistor (actually two transistor's arranged as a Darlington pair). I removed the buffer from mine (shown in earlier pics) as part of the true bypass mod (stinkfoot true bypass mod). 6 components including the MPSA13 have been removed, though the instruction also shows how to true bypass without removing the buffer by cutting circuit board trace's. You can see on mine the twisted yellow & white wires that jumper the guitars signal from the circuit board to the footswitch & back. I imagine the buffers components make up the parts on your board that aren't on mine (adjacent to input jack), but post a pic of your board if you like. Here's a schematic showing the values for the Hendrix, Wylde & Dime wahs
Note the Dime wah (DB-1) has a higher inductance value (slightly). Cheers

 

[Catmandue]

The Centec hfe tester don't work worth a squat. It also might be that these are bogus ( bad ) transistors. I'll have to try it with some other transistors. My project never worked very well and I believe it might be bad transistors. I'm going to try them with other transistors when I get some. I know I can use the leads to test also. I saw a video on youtube showing me. They got a demo for everything on youtube. LOL. These trannies I have are 2N3904.

 

[ivan H]

The 2N3904 is an NPN type, here is the pinout
It will need to be tested in the NPN socket (PNP's have opposite polarity). The pins need to be in the correct sockets (E B C) & can sometimes need a bit of a jiggle so that all pins make proper contact. But yes, if you cant get a reading they may be fried or something. Hope this helps. Cheers

 

[Catmandue]

The 2N3904 is an NPN type, here is the pinoutView attachment 5809
It will need to be tested in the NPN socket (PNP's have opposite polarity). The pins need to be in the correct sockets (E B C) & can sometimes need a bit of a jiggle so that all pins make proper contact. But yes, if you cant get a reading they may be fried or something. Hope this helps. Cheers

Ivan, I just picked up today some other fresh transistors I don't know if these are of value to modding in general but, I got them for a decent price. I can try to post pictures if you like to see them along with shots of my JH-1 wah board. The new trannies I got are 2N3906 ( five of these in a pack ) and some metal ones that say audio UHF on the pack they are 2N2223A ( two of these in a pack ). Do these have potential for modding projects? I also picked up some pots. I need to clean or replace the volume on my 78 P Bass. It has a crackle when I turn it now and cuts out some at times or, drops in volume. By the way are all all NPN transistors have the EBC pattern and PNP have CBE?

 

[Catmandue]

By the way, Small Bear carries the 2N3391A tranny but, I did not see the 2N3900A on their site. I do see the 2N3900A from a few vendors on ebay. Is that a good option?

 

[ivan H]

Hi C man, pinouts can vary from device to device whether they be PNP or NPN. The 2N3906 is a PNP type that you might find use for in stompboxes, eg, the original Roger Mayer/Hendrix Octovio was a positive ground circuit that these can be used in. The 2N2223A I'm not familiar with but appears its a dual transistor. I don't know any more on. For the 2N3900A, if you want the low noise part, yes. Cheers

 

[Catmandue]

Ivan, I just tracked down and ordered 2n3900a and 2n33911a trannys, like the ones that Dave Weyer used on Hendrixs' wahs. I also plan on put a 1 K ohm trimpot on the spot where you got the ball point pen pointed in the top photo. I'll probably adjust by ear close to the way I adjust the GCB-95 you helped me to cherry out before. I got a feeling the ohm settings on this one will vary a bit from the GCB-95. I'm going hold off on replacing the inductor on it. The pot is still working great on this wah. I don't believe it was greatly used when I picked it up. I may go with an inductor like the one you show in the photo above. I'll play that one by ear. Maybe I'll be able to dial in the OEM one just dandy and not have to change it.