Help with SI Fuzz Face kit from bigtonemusic.com

[superhombre2k]

I'll follow Fret Wire's instructions too, for the purpose of thoroughness (is that a word?)

[superhombre2k]

Here you go:

E1 = 0v
B1 = .4v
C1 = 2.25v

E2 = 1.25v
B2 = 2.35v
C2 = 5.5v

[Fret Wire]

Just measure right on each of the transistor's three leads. Looking at the bottom of the transistor, the base is in the middle, the emiter is the side with the little tab, and the collector is the other side. The seller shows you on this diagram in the instructions. All three measurements on each transistor is important.

http://www.bigtonemusic.com/fuzzclonetransistors.html

[Fret Wire]

Gettin' there. Here's some baseline voltages you should be shooting for:

Q1 E-0
    B-.1
    C-.5

Q2 E-.4
    B-.5
    C-4.5 (or half supply voltage)

What was your battery voltage? C2 should be 4.5-4.7v. You'll have to adjust the 8k2 resistor.

[superhombre2k]

From the battery to ground, it's reading like 16.5v... what the hell?

[Fret Wire]

What's the actual voltage your battery is putting out measured directly?

[superhombre2k]

I have the precision set to 50v DC and it's putting out 16.5v when measure directly from the terminals.  I took another new battery I had and it read the same.  Maybe I should get a new multimeter.  Did any of my other values seem off too?

[Fret Wire]

New 9v's usually run around 9.4 volts. Tomorrow, if you can borrow a DMM that you know works, remeasure and post your transistor voltages.

[superhombre2k]

I'm just using an analog one right now and I don't know anyone with a digital one.  How much do they run?  I might as well get one.

[Fret Wire]

Something like this will get you by relatively cheap. Does all the usual checks. Anologs aren't bad, but can be hard to read for some.

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=22-813

[superhombre2k]

I'd feel bad if I ruined my Dad's by having it on the wrong precision initially... I'll try to swing in tomorrow to Radio Shack and pick a DMM up.  Maybe he won't notice if I swap'em!

Just out of curiosity, I set it for 250vAC and stuck the probes into the outlet on my wall and it said 225v.  I think this thing is pretty @#$%ed up considering it should read 120v.

[ErikMiller]

There are many better places than Radio Shack to obtain a good, inexpensive DMM.

http://www.circuitspecialists.com/
http://www.techbuys.net/
http://www.harborfreight.com/
http://www.futurlec.com/

At most of these sites, for under $10, you can get a DMM that will measure transistor hfe, which is pretty handy for Fuzz Face tuning. As far as I know, none of Radio Shack's meters do this. Maybe they are afraid that people would find out how far out of spec their crappy parts are.

BTW, I'm sorry I worded my measurement instructions poorly. You want to measure the voltage between the collector of the 2nd transistor and ground. Make this measurement with the Fuzz control all the way up.

[petemoore]

Kwik try a new battery in the meter.
 The internal battery is used as a comparator, when it gets low, the V readings will read high.
 I still use hafff dead battery, but don't use the actual V readings, when all I need is a percentage reading...say if I'm trying to find 1.2v...if it says 16 on the meter, try getting 8v at Q2 collector...haw, try replacing the MM;s battery...

[superhombre2k]

Gettin' there. Here's some baseline voltages you should be shooting for:

Q1 E-0
    B-.1
    C-.5

Q2 E-.4
    B-.5
    C-4.5 (or half supply voltage)

What was your battery voltage? C2 should be 4.5-4.7v. You'll have to adjust the 8k2 resistor.

OK, I got a DMM today and here's what I measured from ground to each of the transistor legs, as well as the battery's voltage.

battery = 8.26v

Q1
E1 = 0
B1 = .58
C1 = 1.32

Q2
E2 = .7
B2 = 1.31
C2 = 2.3

I checked the indicated resistance to the actual measured resistance on all my resistors to make sure everything was ok and all of them checked out within reasonable parameters, except for the 330ohm one.  It was out of the range of the DMM on every setting (screen read OL).

Well, I'm one step closer to getting this circuit working right!

[ErikMiller]

OK, I got a DMM today and here's what I measured from ground to each of the transistor legs, as well as the battery's voltage.

battery = 8.26v

Q1
E1 = 0
B1 = .58
C1 = 1.32

Q2
E2 = .7
B2 = 1.31
C2 = 2.3

I checked the indicated resistance to the actual measured resistance on all my resistors to make sure everything was ok and all of them checked out within reasonable parameters, except for the 330ohm one.  It was out of the range of the DMM on every setting (screen read OL).

Well, I'm one step closer to getting this circuit working right!

Okay. Yeah, I thought you'd see a low reading on the collector of Q2. 330 ohm resistor? I guess that differs from the diagram on the www site. Not uncommon for Si 'Faces to have that value.

If you want more oomph from it, bump that resistor to 470 (it sounds like it may be suspect anyway), and drop in a 6.8K or 6.2K or even 5.6K in place of the 8.2K. The important thing is to adjust that 8.2K resistor down until you get about 4.5V at that collector. Some people put in a 10K adjustable resistor, but I don't like trimpots.

I predict you will be stunned at how good it sounds!

[petemoore]

...suggest socket Q2 resistor...if possible, then you can plug in resistors there...[unless you can 'wangle' a trimpot in there]
 or hook a 20k er so pot up with wires [or another socket] dial it to the resistance you want [using DMM] plug that in the R socket, dial in the bias, then without moving the pot's shaft, remove and measure the resistance of the pot, and place a close to that value resistor or build a resistor of the value you want and plug that in there, good sockets don't need this but I've heated the socket wiper from the resistor lead, and soldered resistors and other items right into the socket on one side so they don't fall out.

[Paul Perry (Frostwave)]

you can get a DMM that will measure transistor hfe, which is pretty handy for Fuzz Face tuning. As far as I know, none of Radio Shack's meters do this.

Certainly RadioShack (or Tandy as it was here in Australia) is crap now, but ironically, bacck in the Good Old Days, Paul Schreiber (who designed the Moog Concertmate for them) designed and patented a DMM with a transistor checker function that actually showed which pins were what!!
Well times have changed..

[Fret Wire]

http://www.anatekcorp.com/testequipment/atlas.htm

It's a beauty. The first time I saw it, I thought about it for a minute, and bought a capacitance meter instead.

[superhombre2k]

OK, I got a DMM today and here's what I measured from ground to each of the transistor legs, as well as the battery's voltage.

battery = 8.26v

Q1
E1 = 0
B1 = .58
C1 = 1.32

Q2
E2 = .7
B2 = 1.31
C2 = 2.3

I checked the indicated resistance to the actual measured resistance on all my resistors to make sure everything was ok and all of them checked out within reasonable parameters, except for the 330ohm one.  It was out of the range of the DMM on every setting (screen read OL).

Well, I'm one step closer to getting this circuit working right!

Okay. Yeah, I thought you'd see a low reading on the collector of Q2. 330 ohm resistor? I guess that differs from the diagram on the www site. Not uncommon for Si 'Faces to have that value.

If you want more oomph from it, bump that resistor to 470 (it sounds like it may be suspect anyway), and drop in a 6.8K or 6.2K or even 5.6K in place of the 8.2K. The important thing is to adjust that 8.2K resistor down until you get about 4.5V at that collector. Some people put in a 10K adjustable resistor, but I don't like trimpots.

I predict you will be stunned at how good it sounds!

I replaced the bad 330 with a 470 today and I'm going to try a 5.6k instead of the 8.2k (I ran out of time this afternoon before work, and now I'm home again!)  I'll post more as I do more...

[superhombre2k]

As per ErikMiller's advice, I replaced the 330ohm resistor with a 470ohm resistor "for more oomph" and the resister after Q2's collector with a 5.6k instead of the 8.2k which it came with (and which measured right around 9.4k when I checked after removal it out of curiosity!!  yikes!!) again for more output.  The point of me modding it this way is because I found unity gain to be too high.  I wanted unity to be around 50% or lower on the volume pot instead of almost all the way up.

Alright!!  Here are the final values!  (At least until I go under the hood again!

battery = 8.73 (newer battery)

Q1
E1 = 0
B1 = .58
C1 = 1.25

Q2
E2 = .65
B2 = 1.25
C2 = 4.8


Thanks to everyone who stuck around and helped be figure this @#$%ing thing out!  I have successfully completed my very first pedal!