Fuzz Face Boutique problem...

[ZeRoTrE]

Hi to all.
I made the boutique late 60 FF PNP positive ground from GGG. I've used two ac128 and a pair of ac122, germanium transistors.

http://www.generalguitargadgets.com/diagrams/fuzzface_b_lo_pp3.gif

I've made no changes with components or wiring..

When i first use it, it worked great (ac122) no problems, i could turn the 10k trim on one side to the other with no problems.
Then i've put the ac128, but this time when i power on the battery there was a lot of noise, when i turn the trim-pot the noise becomes to much...
Then i changed the transistor, but now also the 122 make noise....(??)

Some value...


Battery -> 9.00v
power on -> 8.05v

ac128 (trim turned on right)

Q1
C 0.64
B 0.1
E 0

Q2
C 1.60 - 1.67 (the voltage isn't stable....)
B 0.64
E 0.52

Ac128 (trimmer turned on left)

Q1
C 0.74 - 1.30 (voltage not stable)
B 1.27 - 1.42 (voltaqe not stable)
E 1.07 - 1.24 (voltage not stable)

TIA
Best regards..
Zerotre.

[ZeRoTrE]

I'm trying to adjust the 10k trim so it doesn't make noise, it seems quite ok, i've read about a ge diode that i can put to the transistor, i've some OA91 could i use them? Any suggestion?
Hi,
Zerotre.

[ZeRoTrE]

Hi
i'm going mad

Sometimes it works very well, then i shutdown the ampli, after one hour i power on and i get the scratch....it seems like an old disc.
Please help me...

q1 122 hfe 160
E 0
B 0.124
C 0.87

q2 122 hfe 110
E 0.74
B 0.86
C 2.90

Regards.
Zerotre.

[petemoore]

Those pesky 2Q Feedback R amps!!!
 They can be tricky to debug, somethings wrong there with the Q2 bias...
 Way I try doing it after general looking at's is...looking at the schematic and checking on the board with the DMM.
 Check resistor values...for resistors with alternate current path through the circuit [besides throughthe R] disregard, 'calculate' [tricky math there] or pull one end...disregard is recommended.
 Run through every path in the circuit with whatever test you can think of DMMing it...
 Check for continuity between resistor leads and say transistor socket lug or lead. Check for continuity ... theres lots of places to check this, between Q1C and Q2B is an example.
 It's not like debugging a 1Q gain stage...everything has to be 'right' for it to work.
 Finding the problem was easy, finding solution is the tricky part...all I can do is tell you what I know how to do ^ ...maybe someone else can calculate a solution from those numbers..

[ZeRoTrE]

I don't know if i make it right, however i take some voltage values about q2 and q1, i also test the connection, i've remelted all the solder point... (it's strange, when the solder point are hot there is no noise.....)

dmm black to the Q2E

red on:
R11(pos line) 0.51 0.61(voltage not stable) <--- lead of R1 that is connected with the positive line
R11 (pot volume) 0.31 0.43
R1 (pot bias) 0.48 0.61
C1+ 0.48 0.58
C1- 0.25 0.45
R2 (negative line) 8.21 8.31
R2 (Q2B) 0.10 0.12
R9 Trim pot (R5) 6.21 6.74
R9 trim pot (Q2C) -2.17 -2.21
R5 (R4 C3) 6.93 7.21
R4 (pot contour) -7.14 -7.48
C3 (pot volume) 0.38 0.45
C2- 0

Black dmm on Q2B

red on:
R11 (pos line) 0.63 0.75
R11 (pot Volume) 0.41 0.50
R1 (pot Bias) 0.63 0.72
C1+ 0.70 0.78
C1- 0.53 0.61
R3 (Q1B) 0.53 0.58
R2 (neg line) -8.03 -8.08
R5 (trim pot) -5.85 -5.96
Trim pot (Q2C) -2.94 -3.30
R5 (R4 C3) -6.58 -6.62
R4 (pot contour) -6.71 -6.81
C3 (pot volume) 0.64
C2- 0.13

Black dmm on Q2C

red on:
R11 (R1 Pos line) 2.92 3.03
R11 (pot volume) 2.24 2.30
R1 (pot Bias) 2.90 3.01
C1+ 2.89 3.03
C1- 2.98 3.10
R3 (Q2E) 2.26 2.35
R3 (Q2B) 1.78 1.84
R2 (neg line) -5.94 -6.00
R5 (trim pot) -3.29 -3.38
R5 (R4 C3) -4.45 -4.61
R4 (Pot contour) -4.75 -4.81
C3 (pot volume) 2.05 2.09
C2- 1.94 2.06
 
Black dmm on Q1C

red on:
R11 R1 (pos line) 0.83
R11 (pot volume) 0.61
R1 (pot Bias) 0.82
C1- 0.67
c1+ 0.83
R3 (Q2E) 0.12
R3 (Q1B) 0.67
R2 (neg Line) -7.90
Trim Pot (Q2C) -1.66 -1.75
R5 (trim pot) -5.17
R5 (R4 C3) -6.36
R4 (pot contour) -0.62
C3 (pot vol) 0.62
C2- 0.13

Black dmm on Q1B

red on:
R11 R1 (pos line) 0.12
R11 (pot volume) 0.09
R1 (pot Bias) 0.12
c1+ 0.12
R3 (Q2E) -0.55
R2 (Q2B) -0.67
R2 (neg Line) -8.60
Trim Pot (Q2C) -2.44 -2.49
R5 (trim pot) -5.88
R5 (R4 C3) -7.07
R4 (pot contour) -7.34
C3 (pot vol) 0.09
C2- -0.56

Black dmm on Q1E

red on:
R11 R1 (pos line) 0
R11 (pot volume) 0
R1 (pot Bias) 0
C1- -0.13
C1+ 0
R3 (Q2E) -0.70
R3 (Q1B) -0.13
R2 (Q2B) -0.83
R2 (neg Line) -8.72
Trim Pot (Q2C) -2.38
R5 (trim pot) -5.90
R5 (R4 C3) -7.13
R4 (pot contour) -7.40
C3 (pot vol) 0
C2- -0.72

If there is some strange value please tell me and i retest them.
TIA
Best regards.
Zerotre.

[Giaime]

You surely have oscillation. In fact, you say that when the solders are hot, there isn't noise: that's because your iron's tip is making a ground connection for the circuit. Try small value caps to ground at the input, output or between the two transistors.

[stm]

I can tell you about my latest experience with an Axis Silicon FF with positive supply.

1) I used hfe 70 for Q1 and 125 for Q2 (within the usual recommended range). It sounds OK, relatively low noise, etc. I decided to try 2N3904 and 2N2222 transistors (hfe over 180 on all of them), and the thing went mad, with lots of hiss and noise.

2) Your transistors are high gain, and also you mention using the hfe 160 on Q1 and hfe 110 on Q2. Usually the low gain goes first, so this may be playing against proper biasing.

3) You say when placing the soldering iron it works. Ge trannies are very sensitive to heat and their leakage and hfe characteristics change a lot. Seems like when you apply heat the parameters drift to a more stable biasing point. It is well known that Ge FF are very picky about temperature, and their sound can go from great to crap depending if you are playing under the sun or on a cold day.

4) How did you measure the hfe's? A leaky Ge transistor may show a falsely high hfe, so your 160 hfe transistor could be in fact way less. This is greatly explained in http://www.geofex.com/Article_Folders/ffselect.htm

5) Try to see if some silicon PNPs like 2N3906 do work there (just to discard other problems). Do you have sockets for exchanging transistors?

Good luck!

[ZeRoTrE]

thanks a lot for the help...

I've read about ge and temperature but this thing is really strange.
I've also read about to use a ge diode to the Q2...
About the caps where must i put them? I'm not really an expert...

I've ac128 40-50 hFE, ac128 60-70 hFE, ac122 100-110 hFE, ac122 150-160 hFE, (hFe value from the shop where i bought them).
I try different combinations, but i get always the same thing.

Bye
Zerotre.

[petemoore]

I'd use sockets first, heating these transistors with a soldering iron is not recommended, That way they can be easily swapped without damaging them.
 I'd use 2n3906, just to see if the thing'll show 'ballpark' voltages, and also half way fire up [sound may be gatey, but you'll probably be able to tell.,..like an engine that 'Pops' after cranking cranking cranking...you know when the thing  'acts like it wants to'...then probably can be tuned from there into operating conditions [bias voltages] that provide good FF function.
 Once the circuit acts like it 'wants to' and no really wierd voltages are seen, I'd put in the AC128 60-70 for Q1 and one of the last two [higher hfe than Q1] for the Q2 position.
 When a FF board IS right, and Q's of reasonable applicability [leakage and Hfe]...or even close...should be able to be dropped in and Q2 trimpot adjustment should cause the Cct to show reasonable bias voltages and FF tone...if not...well somethings not right...
 You've done extensive work here documenting the readings you've taken...
 In there somewhere is probably a clue....I'll read through it more if you do also...generally those readings are probably best analyzed 1 by 1 as they're taken, referring to the schematic ... and the voltage readings ... and the resistance readings ... somewhere in that 'pile of hay' is a clue to exactly where the 'needle' is, the one that is causeing the problems....
 I just verify what I can using the DMM for EX: that 33k exists actually between Q1C and The top power rail looking at schematic....or 100k between Q1B and Q2E...
 Somethings keeping Q2C at a low voltage...should be 1/2v or so....

[ZeRoTrE]

Thanks for the answer.
First of all, if it's possible try to explain it more simple  :lol: , i must translate the words before in italian then i must understand the words about electronic.... :lol: it is not very simple for me because i don't know the two arguments well.
Then if i've understood well, now i must take some resistance value from the trannies and the other components?

I'm not using a box (yet), could be some emc?
I've only some 2n2222, could i try with these? Must i use all SI or Q1 GE and Q2 si?
Thanks a lot.
Best regards.
Zerotre.

[stm]

The 2N2222 are NPN transistors, while your circuit is intended for PNP, so you can't use them in your circuit.

The transistor usage suggested by petemoore should work fine. Maybe your problem is either an error in the wiring, or some component with a wrong value, like placing a 330k resistor intead of a 33k resistor, etc.  

Also, you must be absolutely sure you are connecting the transistors correctly, meaning "base goes here", "emitter here", "and collector there". Get a datasheet for the transistors and check carefully.

[petemoore]

ICR...but lotsa times, I put in a 470k where the 470 goes...don't work that way...I tried it at least a few times...lol.

[ZeRoTrE]

Some pics of the circuits, i've download all the datasheet and checked the resistor (although i can make it wrong anyway )

remains strange the fact that sometimes works and some doesn't.

ps. i've always used the socket for transistor, but in the last option i've soldered them to check if the sockets could have problems.

Thanks to all, i'm happy to have someone that helps me.
Ciao/regards
Zerotre.






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[Giaime]

Wow! Another italian! Where are you from? I'm from Venice...

[ZeRoTrE]

hi Giaime,


I'm from Cosenza, south italy...


What about if i change the circuit to the pnp negative ground?


Bye.
Zerotre.

[petemoore]

First decide what transitors your'e going to work with..
1  For NPN, use Neg Ground Schematic
2  For NPN, use POS Gnd. Schematic.
 I was of no help with PNP POS GND... many changed their board from this supply setup to one of the first two mentioned.
 To invert polartiy function of a FF [like if you wanted to switch from PNP Pos Gnd to NPN Neg Gnd..or starting from the opposite PS scheme..going PG to NG...]
 Just change all polarized components, for FF that means at least the V+ and V_ [red and black battery clip leads], and the polarized 22uf cap.
 If any other caps are polarized, the polarity symbol on the cap that matches the sign of the schematic [neg or pos] must connect to the circuit side ...
  example for input cap, on a neg ground circuit, the - would go to Base/100k node  connections. Output cap on same circuit, if polarized goes - to circuit/the 470ohm/trimpot connection.
 After changing the power supply rails, I'd recommend referring to the applicable schematic and check that all the parts on the board with + or - are correctly polarized.

[ZeRoTrE]

Hi,
i tried to make the pnp neg version that is at GGG, but there is always the same noise... :cry:  :cry:
Remains the hammer...
Bye.
Zerotre.

[ZeRoTrE]

This is reaaly fun, i've finished now the phase 90 that works great (i hope it will work in the future...), really amazing sound, but also really difficult project specially with a breadboard, the matching fet and a simple circuit like the ff doesn't work.....
Bye
Zerotre.

[petemoore]

Gotta love that 90...seems to like various inputs just fine, has that ph90 tone...great phaser !