Need help with Hendrix JHF1 fuzz face input trimpot mod

[dwrockdoctor]

Hi everyone, my first post here and my first question!

Basically, I want to add an internal trimpot to the input of my Dunlop Hendrix JHF1 fuzz face. I usually find that the most usable tone I get out of this pedal is when my guitar volume is lowered to about 8 on the dial and want to get that tone with my guitar volume on full. I have basic soldering skills but am a complete beginner at reading a schematic and I am having trouble finding out which of the colored wires connecting the circuit board is the one running from the input jack to circuit board so I can wire in a trimpot...

Here is a schematic I found online of the Hendrix fuzz face:



My guess is the that the pink line in the diagram going from the top lug of the input jack to the circuit board is the wire that you would solder an internal trimpot onto between the input jack and circuit? Here is a photo of the fuzz face circuit board and an arrow that I added pointing to the brown wire that I think is indicated by the diagram I added earlier...



This brown wire is going to a terminal on the circuit board labelled TP2. Is it as simple as unsoldering this brown wire from the circuit board and adding a mini input trimpot between the brown wire and the circuit board at TP2?

Sorry if my terminology and knowledge is primitive, I am basically a complete beginner but am willing to learn and would appreciate any help

Cheers everyone!

[Govmnt_Lacky]

Here is a schematic I found online of the Hendrix fuzz face:



My guess is the that the pink line in the diagram going from the top lug of the input jack to the circuit board is the wire that you would solder an internal trimpot onto between the input jack and circuit?

You would install the trimmer between the BLUE wire on the lower right corner of the switch and the switch itself. That way the "reduced volume" input would feed both the effect and the bypassed signal.

[dwrockdoctor]

Thanks for that mate. Not sure if I want the trimpot to effect bypassed signal too though... I want to click the fuzz face on and have the sound of what it sounds like at the moment with the guitar volume on 8 (basically removes excess farting out and cleans it up a bit) but when bypassed it goes back to the sound of guitar volume on 10. Which wire on the diagram would this be?

[Govmnt_Lacky]

Thanks for that mate. Not sure if I want the trimpot to effect bypassed signal too though... I want to click the fuzz face on and have the sound of what it sounds like at the moment with the guitar volume on 8 (basically removes excess farting out and cleans it up a bit) but when bypassed it goes back to the sound of guitar volume on 10. Which wire on the diagram would this be?

What you are not taking into account is that your guitar volume in BYPASS will be on 10 but.... the guitar volume coming out of the JHF1 will essentially be on 8. So, when you click over the footswitch between the fuzz and the bypass, you will have a difference in volume from 10 to 8 -OR- 8 to 10.

If you do not mind this volume difference, then install the trimmer at the signal input of the circuit board. If you DO NOT want the volume difference, then install the trimmer where I mention above.

Good Luck 

[dwrockdoctor]

Okay, thank you very much, that is what I am going for.... Getting my bypassed sound the same as the guitar on 10 and then the fuzz face signal is equal to guitar on 8. With the volume and fuzz on the fuzz face up near full I don't think there will be too much of a problem with volume drops etc anyway, I just want that beautiful cleaned up fuzz face overdrive without having to lower my guitar volume every time I engage it.

One more question and please bear with me... Looking at a few basic silicon fuzz face diagrams floating around and looking at the circuit board on my fuzz face, I suspect that the yellow wire is actually the signal input of the circuit as it is the one connecting to the C1 transistor (which all basic silicon fuzz face circuit diagrams I have seen seem to be where the input first hits the circuit board). Here is a picture:



The yellow wire at the right bottom hand of circuit board in the picture is connected to the C1 transistor (2.2uf), would this be the signal input and where I would solder in a trimpot?

Again, thank you for your patience in helping out a complete noob, I am starting to read around and understand more but it's a bit like reading chinese still and could use a helping hand

[dwrockdoctor]

Sorry, I just realised I meant to say capacitor, not transistor, in relation to the C1 spot on the Hendrix fuzz face circuit... I've got a lot to learn, ha ha 

[Govmnt_Lacky]

The yellow wire at the right bottom hand of circuit board in the picture is connected to the C1 transistor (2.2uf), would this be the signal input and where I would solder in a trimpot?

YES.... however, keep in mind that you WILL have a volume difference between your clean guitar and fuzz guitar if you solder the trimmer here. In simpler terms, if you solder the trimmer at the fuzz input, with your guitar set to 10 and the trimmer set to 8..... when you switch from clean to fuzz you WILL experience a volume drop 

And vice-versa. When you switch from fuzz to clean, you will get a volume increase. If that is what you want... go forth and install the trimmer at the circuit input.

If not, install the trimmer at the footswitch but, you will be getting an 8 at the output with clean AND fuzz even when your guitar is set to 10.

[dwrockdoctor]

Okay, I will keep this in mind and thank you very much for all your help

[dwrockdoctor]

I forgot to mention also that I am using the fuzz face on an already overdriven amp sound. I haven't noticed any difference in volume when I switch in the fuzz face and quickly roll my guitar volume down to 8 compared to when I switch back to the amp sound with guitar on 10 so I'm guessing that putting the trimpot on the yellow wire before the C1 capacitor would yield similar results to this... Time will tell, ha ha, thanks for the help.

[wavley]

The yellow wire at the right bottom hand of circuit board in the picture is connected to the C1 transistor (2.2uf), would this be the signal input and where I would solder in a trimpot?

YES.... however, keep in mind that you WILL have a volume difference between your clean guitar and fuzz guitar if you solder the trimmer here. In simpler terms, if you solder the trimmer at the fuzz input, with your guitar set to 10 and the trimmer set to 8..... when you switch from clean to fuzz you WILL experience a volume drop 

And vice-versa. When you switch from fuzz to clean, you will get a volume increase. If that is what you want... go forth and install the trimmer at the circuit input.

If not, install the trimmer at the footswitch but, you will be getting an 8 at the output with clean AND fuzz even when your guitar is set to 10.

Unless he uses the volume knob on the fuzz face to make up the gain lost.  My fuzz face has a pre-gain control and I just turn the output up when I turn the pre-gain down, I still have pretty much unity output either way.

[Govmnt_Lacky]

Unless he uses the volume knob on the fuzz face to make up the gain lost.  My fuzz face has a pre-gain control and I just turn the output up when I turn the pre-gain down, I still have pretty much unity output either way.

Agreed 

[dwrockdoctor]

Hi again. I just dropped into my local electronics store today and picked up a couple of 50k mini trimpots that are the same as these ones pictured:



My question is about how to solder this before the C1 position on the circuit board. Can I just desolder the yellow wire connected to the C1 capacitor and solder the middle pin of the trimpot (the one that is sitting all by itself on the opposite side of the two outside pins) directly into that signal input point at the TP1 to C1 position that I pulled the yellow wire from?

Then is it just a matter of soldering the yellow wire to either of the two other pins grouped on the opposite side of the single pin?

Any advice would be greatly appreciated, thanks!

[Govmnt_Lacky]

Why not solder it on to your footswitch so it wont be floating around?

According to your diagram above, Wiper (the leg thats all by itself) goes to Left/Middle lug and one of the other legs goes to Left/Upper lug.

[dwrockdoctor]

I think you might have misunderstood. What I meant is can I solder the wiper pin of the trimpot (the leg that is by itself) directly into the circuit board hole that would be left when I desolder the yellow wire connecting to the C1 capacitor?

This would mean the trimpot is directly soldered to the circuit board and is not floating around and then I could just solder the yellow wire to one of the left or right pins/legs, is this do-able?

Hopefully that makes sense, ha ha

[Govmnt_Lacky]

I think you might have misunderstood. What I meant is can I solder the wiper pin of the trimpot (the leg that is by itself) directly into the circuit board hole that would be left when I desolder the yellow wire connecting to the C1 capacitor?

This would mean the trimpot is directly soldered to the circuit board and is not floating around and then I could just solder the yellow wire to one of the left or right pins/legs, is this do-able?

Hopefully that makes sense, ha ha

Yes you could! 

[joegagan]

use caution mounting these dainty trimmers. the legs can easily snap off if there isn't solid support of all three legs.
if the pedal were mine, and i did not care about the originality of the pcb, i would drill three holes for the legs, and possibly use a dab of duco cement or hot glue to assist in supporting it.

[dwrockdoctor]

Okay guys, thanks for the advice

[dwrockdoctor]

Hi again, just an update, I went ahead with the mod and added a 50K trimpot to the input of the JHF1 circuit. It helped clean it up a bit but not enough to how I wanted it so I went back down to my local electronics store and got a 250K trimpot. After replacing the 50K pot with this I must say I am pretty happy with the results.

I pretty much dial the trimpot down to about 30% of it's rotation (I'm guessing at what would equate to about 3 out 10 in it's rotation). It cleans up the coughing and farting out nicely so it is operating like a nice fuzzy overdrive whilst still having that beautiful fuzz face flavour. It works great in my two main active bands, one of them which is a psychedelic stoner rock band (think Pink Floyd cross with Kyuss/The Sword), I have my two amps, which are an Orange Rocker 30 and Peavey 5150, set to a hot rodded AC/DC style grind and when I kick in the fuzz face I get a nice increase in low end girth and sustain with that great fuzz face fuzziness on top 

For my new blues rock power trio it works wonderfully to push my blues rock set up (Orange Rocker/Ibanez TSA combo) into more Creamy/Hendrixy style tones in conjunction with my Maxon OD808.

One unexpected bonus... my Dunlop Hendrix Wah now plays nice with my newly modded fuzz face I am very stoked about this as I was always having to switch the fuzz off when I wanted to use my wah but now I don't have that problem.

I want to say a big thank you to everyone that helped me to figure out how exactly to do this mod, I am now keen to move onto my first fuzz face build (looking at the GGG 60's boutique fuzz face kit). Yay!!!

[joegagan]

appreciate the report! glad you got a good result.

i also prefer 250k for input gain control on FFs. ( wired like a guitar vol control, last lug grounded)

you might like my easyface, it gets many rave reviews. try the one with input cap blend.

here is another happy review that just showed up this week:
http://www.mylespaul.com/forums/pedals/205438-joe-gagan-easy-face-fuzz.html

[dwrockdoctor]

Out of curiousity Joe, apart from the obvious grounding you get from grounding the last lug, is there any tonal differences from attaching a ground to that lug?

The easyface was one I was considering for my first build too... The great thing is that the kits are generally pretty inexpensive and I love the fuzz face tonality so much (some of my favourite tones are David Gilmour on Pink Floyd's Live at Pompeii and Hendrix BOG and Live at Woodstock) that I'd be happy to end up building a couple different one's over time