first fuzz face build questions

[gdmart]

hello I finally got fuzz major fuzz infact.When the 1k fuzz pot is at 10 i here am radio and therimin type sounds.how do I fix this?
     My fuzz seems compressed, loud but compressed, like it needs to be opened up some what .any one got any advice?Im going to try the famed hendrix mods on this one,  when i can find a 2k audio pot .could i use a 5k pot with a 2 k resistor?.I dont know the exact method to check bias.could some one explain it one more time thanks.

[b_rogers]

use a dvm to set to d.c. volts. touch the black probe to circuit ground, and the red probe to Q2 collector. it should read 4.5 - 5.5 volts.   which version did you build? silicon or germ?   give us some more info and im sure some of the nice folks here can get it running correctly.  FWIW, it sounds misbiased to me.

[petemoore]

I've used 5k's for FF gainpots.
 Just trim it down by finding the value you like, solder a resistor across the pots outside lug. Starting with a 5k resistor, which should bring the pot circuits resistance to 2k5, but use a 4k7, and work your way down depending on pickup output, till the gain knob acts the way you like it to, I like leaving it so it goes 'over the top' of the sweet spot for gain, that way I can use the knob to set gain high enough if I swap trannies.
 2k2 seems to be enough for my tastes^.
 All the PNP Ge's Ive used, their leads form an arrow pointing toward output, I use grab bag 3906's for initial testing, to avoid bad's like reverse polarity happening to the Ge's.
 I'm Using a board mount trimpot for Q2 collector, unless I know the proper bias resistor value for the matched pair. Makes biasing the FF a breeze, in the absence of a pot, I've used a socket for that R.

[gdmart]

Thanks for the info I found that Im close to the benchmark voltages as far as biasing .c was 4.7 b was .2 and e was 4.5.
I found a 5k pot and added a 2k resistor,then did the  hendrix mod including a 100k volume pot ,what a difference this mod makes everything seems opened up not compressed at all.tried it with my strat and it sounded good ,tried it with a 175 gibson and it was darker but my lp with dimarzios really was over the top.the radio interference is minimal unless the gain is on ten. please explain again what value resistor to add to the tranisistor and where? why does this work??.Ive now tested the bias reading with the mod and  c is7.9 b is now .4 and e is now 8.0 would that be right for this mod,I dont know?  thanks

[petemoore]

1rst thing to look at in biasing a FF is Q2's voltages, Q2's collector.
 Easiest way to bias an otherwise properly wired FF is with a trimpot replaceing Q2's collector resistor. If you hook your voltmeter to it [and black to ground] the voltage reading should go up when turning the pot one way and down when turning it the other. Set it so you can get above or below  around 1/2 supply voltage, [or 4.5v of 9v], then leave it or set it by ear for certain sound.
 When stating Q pin voltages, specify which transistor and pin.
 Also is this a PNP? [too lazy to read through for myself].
 Perhaps I'm not reading the voltages properly, but the voltages look off.

[Fret Wire]

Once it's biased correctly, you should see these approximate voltages:

Q1  C -  .5
     B -  .1
     E -   0

Q2 C -  4.5 (1/2 of your supply voltage, ie. 9v)
    B -    .5
    E -    .4

The voltages will show as + or - depending on if it's NPN or PNP, and which way you hook up your DMM leads. As long as the values are in this ballpark, you'll be good to go. After it sounds good, you can experiment with Q2's biasing, going up or down 1/2 volt to see how it sounds. And double check your transistor pinout.

[petemoore]

I just hook black to ground and figure anything it reads gets a + or - sign.
 Emitter should be the smallest Voltage, the collector the largest V, and the base in the middle.
 Geo has biasing info for transistors and in FF's.

[Alpha579]

Which version are these biasing figures from? because i was under the inpression the pnp ge collecters were going to be closer to ~7v... :?

[Fret Wire]

You're probably thinking of the Rangemaster, or some of the Tonebender variations.

[gdmart]

I went back and retested all voltages after the hendrix mods were in place.I found Q1  c-4.3  b- .2 e-4.3       Q2  c- 4.5  b-.1  e- 4.4.
Im not sure where I came up with the higer values earlier.
Oh Q1 has an oc-44 germ  at 85 and Q2 has a no name germ  at  130.
After installing a 5k fuzz pot with a 3.9k resistor the pot (if Im reading right) is seeing 2.1k this seems to work well and the radio waves dont seem to be coming thru.At this point Id say the Roger M mods have worked ,the sound isnt muddy or as compressed and there is more output.
I got this fuzz pcb from Guitar Gadgets and used the pnp neg ground schematic with 3pdt layout next on my list is a  boutique fuzz also from Guitar Gadgets  thanks guys for all the help

[petemoore]

Q1's emitter should be connected to, and read like ground:  0.0 Volts.

[gdmart]

pete I have 0.02 on the emitter,  if that isnt correct where should I look for the problem?

[petemoore]

Q1 emitter will be at 0 volts when connected to circuit ground which is Always at 0v.
 I don't know what mods exactly you have, but unless theres a small resistor between anything [q1 E...for instance] and ground, ground will read 0v.
 whenever you measure the voltage from ground to ground you'll get 0v.

[gdmart]

thanks pete I have it correct now must have had a bad reading or the transistor was not in the socket fully seated    thanks for the help

[petemoore]

N/P...thanks for the thanks...
 Just good to hear about a FF success..

[gdmart]

i installed a buffer in my vox wah so It would work infront or in back of a fuzz face and it has  worked fine for months with a big muff or stock fuzz face.I finished my gg fuzz face a week ago and in the stock layout everything worked well with the vox wah.Now Ive done the( Hendrix )meyer mods, and with the same wah I get fuzz cancelation in the back posistion. something is very wrong.Is there some reason that the (Hendrix) mod should cause this? where should I start to look?