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Need a verification on a JH-1 wah

Started by Govmnt_Lacky, August 16, 2011, 12:36:41 PM

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Govmnt_Lacky

August 16, 2011, 12:36:41 PM Last Edit: August 16, 2011, 01:10:09 PM by Govmnt_Lacky
I am in the middle of modding a Guitar Research wah to Dunlop JH-1 reissue specs. I have the .01uF sweep cap, the .01uF cap in parallel with the 500mH inductor. All other resistors (metal film), and caps are to schematic.

I am using a special pot (200K) for it but I really do not think it should matter (original called for 470K... reissue uses 100K HotPotz II)

My problem occurs when I install the .022uF cap between the pot's wiper and ground (also connected to pot Lug 1.)  As soon as I make contact with the cap, the circuit stops resonating and I just get that dull treble control  :icon_frown:

ALL of the schemos I have seen of the old models AND reissues show this .022uF cap as part of the JH-1 circuit. I would like a confirmation from someone who has the reissue JH-1 to look at this part of the circuit and see if Dunlop does indeed include this cap. It might be SMD and attached to a daughter board which is soldered directly to the pot.

Appreciate the help  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Exactopposite

#1
August 17, 2011, 12:16:57 AM
http://www.geofex.com/article_folders/wahpedl/wahped.htm

All the info you need is right there

Govmnt_Lacky

#2
August 17, 2011, 06:47:27 AM
Quote from: Exactopposite on August 17, 2011, 12:16:57 AM
http://www.geofex.com/article_folders/wahpedl/wahped.htm

All the info you need is right there

Actually, no it isn't. Although RG does touch on almost every component in the wah circuit.... he DOES NOT address the JH-1 specifically nor does he address the component that I am referring to in my original post.

He also does not provide whether or not the reissue JH-1 wahs have the .022uF cap on the pot.  ::)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Ronan

#3
August 17, 2011, 06:54:24 AM
A cap between the wiper and ground? Can you point to a schem that shows that....just doesn't sound right therefore asking.

Govmnt_Lacky

#4
August 17, 2011, 07:09:04 AM
Quote from: Ronan on August 17, 2011, 06:54:24 AM
A cap between the wiper and ground? Can you point to a schem that shows that....just doesn't sound right therefore asking.

This shows the 470K pot in this schemo:

http://www.aronnelson.com/gallery/main.php/v/WAH-ARCHIVE_/WAH-SCHEMATICS/jh1.gif.html

The reissues use the exact same circuit with a 100K HotPotz II. As shown here:

http://www.aronnelson.com/gallery/main.php/v/WAH-ARCHIVE_/WAH-SCHEMATICS/jh1wah.gif.html
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Brymus

#5
August 17, 2011, 05:24:18 PM
Since thats the only schemo that shows it,I wouldnt add it.
IMO the Clyde McCoy circuit with a .015/.02 sweep cap ,and single coil PU's = Jimi sound YMMV

FWIW I tried bypassing Q1's emitter with a cap for more gain and it killed the wah effect too.
But that looks more like some sort of treble bleed bypassing the wah pot like that.

Edit: try a .001 instead ,and see if some of the wah effect comes back.
I'm no EE or even a tech,just a monkey with a soldering iron that can read,and follow instructions. ;D
My now defunct band http://www.facebook.com/TheZedLeppelinExperience

joegagan

#6
August 17, 2011, 10:19:11 PM
i have seen a few jh1s of different eras, but did not dissect them.

my guess is that dunlop added the .022 to ground at end of circuit to kill some high end and make the modern ( high treble due to buffer ) dunlop circuit sound more 'vintage', 'warm'.

i can't imagine this killing the wah effect, tho. i just did a similar mod to a keeley wah for a customer a few weeks back. only difference was a 100k resistor with the .02 cap to ground. the guy wanted it to have less highs and be less hissy. it worked.
my life is a tribute to the the great men and women who held this country together when the world was in trouble. my debt cannot be repaid, but i will do my best.

Govmnt_Lacky

#7
August 18, 2011, 08:14:07 AM
I would just like someone to crack one open to verify that the cap is even there.

The wah does sound pretty good without this cap but, I told someone that I would re-create the JH-1 for them and this cap is the only thing missing. I don't want to send it off to them saying "It's an exact replica of the JH-1 circuit!" only to hear about it later  :icon_wink:
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

ayayay!

#8
August 18, 2011, 05:03:09 PM
Something tells me you do in fact need that 470k pot. 
The people who work for a living are now outnumbered by those who vote for a living.

Govmnt_Lacky

#9
August 18, 2011, 06:06:32 PM
Quote from: ayayay! on August 18, 2011, 05:03:09 PM
Something tells me you do in fact need that 470k pot. 

That may be.

This is why I am hoping someone with the reissue that uses the 100K pot will open it up and verify.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

ayayay!

#10
August 18, 2011, 08:28:29 PM Last Edit: August 18, 2011, 08:30:16 PM by ayayay!
Maybe.  The other thing is, a .022 to ground seems kinda big, but if it's on more than one schem that way that's probably what it is.  Just seems that would put an awful lot of frequencies to ground.  I could see a .002 being more feasible.  

You've definitely got me watching...

...you double sure you didn't accidentally put a .22 on there instead?  I dunno, just trying to help you thing out loud...
The people who work for a living are now outnumbered by those who vote for a living.

joegagan

#11
August 19, 2011, 12:06:15 AM
(100k )
one of the problems will be making sure that the pot hasn't been replaced. i've seen many late model dunlop wahs, i could possibly help in identifying if the pot date code generally matches the era the wah was made.
my life is a tribute to the the great men and women who held this country together when the world was in trouble. my debt cannot be repaid, but i will do my best.

phaseman

#12
May 22, 2012, 03:11:03 PM
Quote from: Govmnt_Lacky on August 18, 2011, 06:06:32 PM
Quote from: ayayay! on August 18, 2011, 05:03:09 PM
Something tells me you do in fact need that 470k pot. 

That may be.

This is why I am hoping someone with the reissue that uses the 100K pot will open it up and verify.

Hi all!
I'm facing the same issue now  ??? but actually have a 470k pot installed....
Did anyone come to a "solution"?

joegagan

#13
May 22, 2012, 04:19:35 PM
same issue, do you mean you have the .022 cap to ground and it kills the wah effect?
my life is a tribute to the the great men and women who held this country together when the world was in trouble. my debt cannot be repaid, but i will do my best.

phaseman

#14
May 23, 2012, 04:59:36 AM
Quote from: joegagan on May 22, 2012, 04:19:35 PM
same issue, do you mean you have the .022 cap to ground and it kills the wah effect?


Yes, I can confirm that.

During last night, I found the schematic of JH1 on the other forum (pm me for link), and I saw that the cap should be 330p  :D :D :D.
I did this change, the wha effect was back, but I am not sure about the overall difference to the gcb95 (I played with a very low volume, it was 2am...)....
So, these days (if I get the chance), I shall install a switch and make some audio recording (w/ and w/o caps) to post ....

p.s. I do not actually have a gcb95. I bought the pot (hot potzII - 470k) recently, and I did the pcb (using TPs layout) several years a go...but did many many mods.
So basically, I use heavily modified gcb95 (w/ TP's input buffer)  ;)

Best regards,
Marko






joegagan

#15
May 23, 2012, 11:41:23 AM
looking forward to the results.
my life is a tribute to the the great men and women who held this country together when the world was in trouble. my debt cannot be repaid, but i will do my best.

phaseman

#16
June 07, 2012, 08:56:24 AM
Finally, I made a short sample that can fairly illustrate the difference between gcb95 and jh1. I played two phrases, both through gcb95, and than jh1. Actually, by playing through jh1 I mean I engaged those two capacitors (10nF in parallel with inductor, and 330pF between pot lugs). I use 470k hot potzII.
Here is the link for the audio : https://www.dropbox.com/s/9zkzee1ogwnod8t/GCB95_VS_JH1.mp3

Also, the schematic I mentioned in previous post calls for 22nF sweep cap.... The recerding is made with the 10nF cap.

I'd say that there IS a difference, in behalf of JH1   :), in my opinion... The lowend has smoother character and it does not sound as "honky" as gcb95...
(although, this kind of "side effect" can be avoided by some other mods... )

Best regads,
Marko
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