Modifying a Fuzz Face Circuit to Include LED/Power

[roncg41677]

Will do!

[roncg41677]

Here's what I got today:



...and...



Looks like he sent an extra pair of PNP IT3085's as well. I'm assuming from the "HFE" markings that he has measured the gain, and that these should be a more suitable replacement for the original MP38s? The MP's were marked "38" and "39" in pen on top.

Since they are PNP I guess there'll be a little extra work involved... (from diystompboxes, "Reverse the polarity of the Electrolytic capacitors, diodes and the power supply.")?

And the pots are small - very small and have no lugs.

[limbe]

On the link I showed you before http://fuzzcentral.ssguitar.com/fuzzface.php
the very first fuzz,the Arbiter Fuzz Face is identical to the fuzz you are building including polarity so you can compare them.(The only difference is the 470 ohm resistor which is 330 ohm in yours).tjk3052 seems to know what he is talking about and obviously has had experience of the pots that are in the package.Judging from what you both have written it seems that you should invest in better pots.(Smaller than pots in a Japanese Fender?)Till next time .Good luck!

[roncg41677]

Thanks Limbe! Just got the rest of the stuff from PedalParts today, including better pots. I'll post some pics when I get a chance.

The only thing I'm still not clear on is whether I need to change the orientation of some of the parts to accomodate a PNP transistor. How do I tell which way they are oriented in the first place (the caps, diodes and power supply mentioned in my previous post)?

[tjk3052]

I guess we need to know what schem you're going to use. If it is this:



Then only the 20uf and 2.2uf electrolytic caps are polarized. There will be a stripe with "-" labeled on the negative lead. On the battery clip, BLACK is connected to the 33k and 470R resistors. If you are including a reverse polarity protection diode, then the side without the stripe is connected to the BLACK side of the battery.

If you are using a DC jack, make sure you do not share the adapter with other pedals unless they are also positive ground polarity.

[roncg41677]

That is the schematic I'm using

Didn't anticipate this, but there is a pretty steep learning curve for me in figuring out how to read schematics. Working on that one. Are connections usually indicated with a dot on pedal schematics? All of the lines are just blurring together.

Reading the schematic and connecting what I'm seeing on the board is a challenge.

[roncg41677]

Okay, I found this schematic that looks similar, but shows the connections a little more clearly:


The only difference is that it shows +9v to ground instead of -9v in the original arbiter schematic. Since I'm using PNP transistors, is that correct?

Here's what I've got so far. Any help is appreciated!

[roncg41677]

Started drilling the enclosure! It wasn't nearly as hard as I thought it would be. The enclosure was much smaller than I expected. It will be a tight fit, but I think I'll be able to get everything in there.

I'm not sure how I'm supposed to put the trim pot on. It has 3 pins and the board is only drilled for 2 at the 8.2k resistor?

[roncg41677]

Looking again it looks like the +9v does get grounded. I've looked at so many different schematics I was a little lost.

Can't work on it anymore tonight. Hoping I can finish it up tomorrow and plug it in!

Thanks so much for all the help!

[limbe]

A trim pot is of course a miniature potentiometer.A pot can be used as a pot or a variable resistor.When you use it as a variable resistor you use the middle pin.(That is the wiper) and one of the outer ones.When you rotate the wiper with a small screwdriver the resistance between the middle pin and the outer ones will change.(I bet you have figured out all of this already).
Good night.

[roncg41677]

I hadn't figured that out. Would I just ground the third wire then?

[roncg41677]

Well, I finished putting it together tonight, plugged it in, and no sound, even in bypass.

I think I may have wired the switch wrong ? I ended up going without an LED or power supply, and every schematic I could find for the switch had one or the other.

The other thing I'm not sure about is the transistors. I checked them with my DMM in the diode setting, with the negative lead on the base I got a very low readout on one leg and no readout on the other, on both transistors. Didn't have this problem when I checked the other 2 NPN transistors that came with the kit. I tried checking them in the hfe sockets as well and got a very low reading on both (001 I think). If the transistors were bad wouldn't I still get a bypass signal at least?