Unicord Superfuzz

[petemoore]

http://www.montagar.com/~patj/uvspfuzz.gif
 I'm perfing one of these, and losing signal across the 47k [goes to cap to diodes. I measured 47k at the resistor and changed the cap.
 Q2 emitter is 6.73v, seems strange because that socket lug measures 9.87k from ground...late...I started at 10:30, it's 4:30...I've been building an debugging 6 hours straight.
 Maybe it wont look so 'right' so I can change something to get it going tomorrow !!!
 Faint glarby fuzz signal... :evil:

[petemoore]

Actually it's a Univox SuperFuzz [schematics link for Unicord...]
 There's something I can't figure out, since I have no idea what the voltages should be, I'll post them.
 I've been putting the 'X10' checks on it, after building up the board, testing continuity of all the little hard to get contact stuff, including underboard DMM touches, resistance calculations, capacitor changes...
 The transistors that look to have non operative voltages have been mega chekked, to the point of pulling resistor leads and measuring stuff like actual resistance of emitter to ground resistors.
 Here's the voltages readings I took...battery is at 13.9v
 Q1
C 7.24
B1.11
E.24  [looks OK?]
 Q2
C 13.9
B 7.59
E 6.74 [this one's resistances to connections all check OK  :?: ] It's emitter measures 9.87k from ground???]
 Q3
C 8.51
B 6.55
E 6.11  [this ones 'hooked up funny' ... I dunno....]
 Q4
C 2.70
B 3.50
E 2.66  [This ones also hooked up as part of the FWR or... ?]
 Q5
C 2.66
B 3.48
E 2.62
 Q6
C 6.54  
B 1.57
E  .74  [This ones working I think]
 When I pull Q4, I get Fuzz Sound, Sustains then gates. All transistors installed = no sound.
 Trikki Wicket...many of the resistors are above board, as are the ground and V+ lines...so I can see/test what's going on pretty easily, found some stuff wrong early in the debugging, not in the last few hours though...
 I'ts a fairly complex wanker, I'm usually pretty good at getting these things going, figured I'd take a break and type about it a while, hoping in the off chance someone might see something I'm not seeing.
 This ones loopin' me... :roll:

[Dan N]

Pete,

Here are the voltages from a Companion black box SF:

battery 9.47v
Q1
C 5.85
B 0.72
E 0.15
Q2
C 9.3
B 5.86
E 5.2  [2K18 to ground when unpowered]
Q3
C 6.61
B 3.53
E 2.96
Q4
C 1.7
B 2.18
E 1.55
Q5
C 1.7
B 2.08
E 1.55
Q6
C 3.05
B 1.21
E 0.61

Hope this helps!

[petemoore]

Thanks Dan N. for posting those voltages, that pretty much puts the limelight off of Q's 4 and 5...they don't look to have 'normal' bias operations in this circuit.
 I've got a practice, then I'll take another look...

[R.G.]

Q1
C 7.24
B1.11
E.24 [looks OK?]

That one's OK, probably, but your meter is showing 0.9V across the base-emitter. That's probably a meter problem.

Q2
C 13.9
B 7.59
E 6.74

OK.

Q3
C 8.51
B 6.55
E 6.11 [this ones 'hooked up funny' ... I dunno....]

Look at the voltages and think of the criteria for working: (1) about0.6 to 0.7 across the b-e: check! (2) Collector highest, base next, emitter lowest (for NPN) : check! (3) some voltage range to move around between collector and emitter - check! This one's OK.

Q4
C 2.70
B 3.50
E 2.66 [This ones also hooked up as part of the FWR or... ?]

Yes, it's part of the FWR. Hm... Nope, there's 0.9V across the BE - way to high, and the collector is below the base. This one is saturated, no signal comes through.

Q5
C 2.66
B 3.48
E 2.62

Ditto. You are somehow saturating the two FWR transistors. Let's think...
1.8K in the emitters at 2.62V to ground. That's 2.62/1800=1.4ma. That has to come through the collectors, so you have 10K*0.014 = 14.5V which is more than your power supply. So they are both doing what they're told - saturating.

The question is - what is telling them to do so?

It's almost gotta be the bases, and a quick glance at the schematic shows that they bias resistors on one side are 22K/22K, and 100K/100K. I happen to know ('cause I drew that schematic about ten years ago and posted it) that those values are erroneous. The problem with people just copying my stuff is that the errors get copied, too. Those bias networks should have 100K on BOTH bases to + and 22K to ground. That will help you a lot.

Q6
C 6.54
B 1.57
E .74 [This ones working I think]

So do I.

So change those bias resistors and have fun.

[petemoore]

Great Rundown RG !!! Glad you caught something I can try !
 ...brb

[petemoore]

Hey O, WoW, That makes a difference.
 Choke/Splatt/Fuzzstain/Ring/Octave.
 Snarowl, Gnash, THirD NoTe
 Even does attack attenuations a 'la trem sound on 12th fret spattering leads. Very NastyFuzz.
 Thanks for posting all the help Guys !!! Catching that R error...chances of me figureing that one out are slim, that area had me puzzled...Nasty !
 I added one capacitor across the Q1 Emitter R. [.1uf,
 Also it was Q3 sensative. I tried Ge Diodes...Si's.