Fuzz Face question

[rasco22862]

Hi i finshed building the Dallas arbiter from ggg. I used some AC188k, works pretty good. But i have some weir voltages, i mean i bias correctly the collector of q2 replacing the 8k2 resistor with a 50k trimmer, but the others voltages don´t reach the "normal" value. Hear they are:

Q1

E:0
B:-0.08
C:-0.19

Q2

E:-0.12
B:-0.19
C:-4.55

Can i do simething, or is just the transistors?

Thanks

[mountainking]

If it sounds good why worry about whether the voltages are "normal"?

[rasco22862]

Maybe it can sounds better, i dont know.

[mac]

Q1 collector is a little low, maybe near 0.3v to 0.5v
Q2 emiter should be near 0.5v.
But without the data of the Ge and the value of the pot it is hard to say.

mac

[mountainking]

Maybe it can sounds better, i dont know.

Good answer.

[rasco22862]

This is the only information i could find:

[rasco22862]

how should i normalize m voltages?

Thanks

[petemoore]

  ROG has Homewrecker, one of those has many FF type voltage readings..various transistors etc.
  It's reaally just a matter of this and that...bias resistors, transistor gains etc.
E:0 This one is perfect.
B:-0.08 something like that I guess, probably a little higher
C:-0.19  I would like this one better if it was about 1.14v
Q2
E:-0.12
B:-0.19 This one is connected to Q1C as schematic shows.
C:-4.55 What Q2CResistor value made this V reading be what it is?
  I would venture to guess there may be a problem in it, I'd go through and verify w/DMM that everything shown on the schematic is there...resistances and connections/non-connections etc.
  If measureing a resistance from a 'distant' point, some information about path connections can be had at the same time. Ie...example: measure from
Ground, through the wire connection to ground, the wire, the connection of the wire to the gain pot, the value of the gainpot, the connections between the other side of the gainpot, also the transistors connections...socket etc. all with an R reading between two points.

[rasco22862]

The 50k trimmer reads 18k to get the collector of Q2 to -4,5v.

I´m a little confused because when i measure the extremes of the 100 k resistor, i dont get 100k, i get 11k, and in the 33k resistor i get 18k. With 470 ohm its ok, i get 460ohm. I think maybe the caps are affecting, i dont know. Should i change it, or its normal

[petemoore]

I´m a little confused because when i measure the extremes of the 100 k resistor, i dont get 100k, i get 11k,
  Close in intense light and mag glass [if you have] inspection around that R maybe, or lift one end from the board and measure it. 11k is small for a feedback loop there.
  and in the 33k resistor i get 18k.
  I'm beginning to think possibly the DMM is reading funny, test the battery before working with it.
  With 470 ohm its ok, i get 460ohm.
  Probably within the rated tolerance of your resistor, well within the general  +/_10% value, and may very very  slightly reduce output...fine @460ohm, even 330ohm is shown IIRC on a FF type schematic.
  I think maybe the caps are affecting, i dont know. Should i change it, or its normal
  I did find a bad cap the other week, very rare, possible. caps are hard to test, sometimes I guess they show DC across them, I've never gotten a DMM to beep when connected to a cap though. If you are using new caps with voltage ratings above the applied voltage, they're certainly good, I don't remember ever hearing about a new cap, bad, I would debug around them, audio probe through them.
  [the way I test caps is compare them to good caps].
  Something's funny with the 100k or your DMM, I *think 11k as feedback resistor though, would tend to pull Q1 base V toward ground.

[mac]

Have you tesed your transistors using RG method? Datasheet means nothing, in particular with Ge.
My guess is that your ACs gain is near 90-100 and leaks 200uA. In that case the values you got are within the normal ones.
Maybe you need to compare a good sample with yours:
http://www.mikepiera.com/samples/GregV_SunFace_Jam1.mp3

mac

[rasco22862]

Yes, my ac´s are matched with the R.G. way.

[petemoore]

  Bill's DMM was actin' so funny yesterday it made me look stupid almost till I had him pull the battery..about flat..
  We were trying to figure out polarity on charging his drill with a random 12v WW.
  I tasted the battery..flat..stuck the DC jack across it's poles...tasted it again..brighter..left it on there a while, smacked the battery around and hand heated it...DMM started working good.
  I told him get a good battery and how he can extend the lives of his batteries.
  The moral of the story is..if it's 'in there' you can find it and measure it...more than one way.
  To see what your dmm looks like set at 200k range [or >100k whatever], with a 100k resistor, take a 100k resistor and put it across the DMM leads, does it read 11k? 100k? take it off and do it again. That reading should look alot like the reading you'll get on a wired right Fuzz Face with the DMM leads across the 100k. er..I'm pretty sure, I can go check, or you can pull one end of it and test it's actual value [out of circuit].
 

[rasco22862]

I took of the 100k resistor and the DMM reads 100k perfectly, but when i put it back it reads 010k. I dont know what to think, i checked all the pads and there ok.

[petemoore]

  Well while you're waiting for a determinated opinions on the 11k anomolous reading on 100k...
  See, IIRC, I used to measure that 100k as 100k in circuit, ie there isn't an easy enough path around the 100k  when in correctly wired circuit to throw the reading off to a lower value..as a parallel resistance will. There is no path shown on the schematic [that I can find] for a parallel resistance [on the 100k] through circuit.
  Clip that DMM lead to the circuit at the 100k...poke around in 'beep' mode...it's a small circuit so start poking next to the 100k and than just poke everywhere.
  Try the other side of the 100k, same procedure, looking for shorts 'to' [somewhere?].
  While you're clipped to the input side of the 100k/Q1B, test for DC across the input cap
  been a while...maybe I was pulling the Q's out for the 100k R measurement in circuit.
  You have different transistors to put in? like grab bag Si's? or test the B/E diodes on the 128's.