PEACH FUZZ! [NO BIAS???]

[brian wenz]

Hello fingers--
  Yeah, same one.  I'm not using all the switching stuff and I'm wondering if this is affecting something with my bias readings.  Check the earlier posts in this thread for the "modded" schematic and then go to Casey's site [also  posted in this thread]  to compare with the original schematic.
Brian.

[brian wenz]

Hello Casey--
    I can't find that other schematic [the "Peachy Fuzz-type circuit with a 5088 or something in Q2] at your site!    I thought I saw it posted there a couple of days ago......was it removed or am I nutz???
Thanks--
Brian.

[brian wenz]

Hello Hello-
   Anybody out there ?
Brian.

[brett]

Hi Brian

The bias voltage from Q2's collector still stays the same [around 3.5 v - 4v] no matter WHAT VALUE resistor I stick in there, though! WHY IS THIS HAPPENING???

So, even if there's NO resistor, the voltage stays somewhere around 4V?  That would imply that Q2 is turned on enough to "pull down" the power supply voltage.  Do you think that's happening?
Have a look at the schematic and see how much DC bias current might be delivered to the base of Q2.  If it's a mA or more, Q2 *might* be drawing a big current.
Can you measure the base and collector currents of Q2 (both with the "normal" resistor and no resistor) and report back?
cheers

[brian wenz]

Hello Brett--
    O.K. , here's the official readings for Q2 :
   
     With 5.6 res. --    E- 3.70
                               B- 4.28
                               C- 4.70
           
     Without 5.6 res. -- E-3.60
                                B- 4.16
                                C- 3.60

Have you seen the schematic?  [pretty strange values...]
Brian.

[brett]

Hi Brian
I used the schematic here:http://www.geocities.com/munkydiy/peachfuzz.jpg
I'm guessing here, but it seems that WITH the resistor, the transistor is biased normally - there's 0.6B between the base and collector, and the collector is positive wrt the base.  Maybe not perfect, but normal.

When there's no resistor, the collector and emitter are sitting on the same voltage, and the transistor is saturated.  It's bad news whenever the base-collector junction becomes forward-conducting, as in the no-resistor case.  There's a technical term for BJTs operating this way, but it's bascially outside my experience.  (I presume that the reason for the low voltage is that the transistor is drawing heaps of current, loading your power supply).

To make sure that Q2 is indeed working ok, and you aren't just getting output from Q1, you'd need to audio probe on the collector of Q2 (with the connection to the fuzz control broken).  A pain in the butt, really.

cheers

[brian wenz]

Hello Brett--
   Any other way to do this besides the audio probe?
Thanks-
Brian.

[casey]

Hello Casey--
    I can't find that other schematic [the "Peachy Fuzz-type circuit with a 5088 or something in Q2] at your site!    I thought I saw it posted there a couple of days ago......was it removed or am I nutz???
Thanks--
Brian.

i put everything in sub categories.....go to "fuzz and overdrives"

click on that link and you should see it there....somewhere...

[casey]

here it is....

http://photobucket.com/albums/v324/caseyseffectpage/Fuzz%20and%20Overdrives/

[brian wenz]

Hello Casey--
   Nope....it's not there, I must be nutZ!    Maybe I saw it at some other site......dunno...     The circuit was pretty much the same as the "Peachy" but instead of a 2N3565 for Q2 it had a 2N5088  [or something close to that.]   I think I'll try putting  some higher-gain tranny in Q2 of my Peachy and see if that changes anything.
By the way, thanks for your site!!  It has some great schematics on it.
Brian.

[brett]

Any other way to do this besides the audio probe?

Oscilloscope?
Brian, if you don't have an audio probe yet, now is the time to make one.  Just a 0.1uF cap, an alligator clip and an old guitar lead - too easy!
cheers

[brian wenz]

Hello Brett--
     O.k., audio probe it is........an oscilloscope might take longer to make....
Yeah, you're right, I keep putting off making the bloody thing.
 In the meantime, I  put a 2N5089 in Q2 and all the readings are the same, so something about this circuit is treating every tranny the same.
I wish someone would chime in with a "Technology of the Peachy Fuzz" session to explain how this circuit works .........I'm still really concerned that there may be something wrong with the schematic  or that by building it without the switching system I botched it.
Thanks-
Brian.

[casey]

Hello Casey--
   Nope....it's not there, I must be nutZ!    Maybe I saw it at some other site......dunno...     The circuit was pretty much the same as the "Peachy" but instead of a 2N3565 for Q2 it had a 2N5088  [or something close to that.]   I think I'll try putting  some higher-gain tranny in Q2 of my Peachy and see if that changes anything.
By the way, thanks for your site!!  It has some great schematics on it.
Brian.

thanks for the compliment.....yeah, im trying to get a lot of old school
type stuff going....

here is the direct link to the peachy fuzz on my site....

http://photobucket.com/albums/v324/caseyseffectpage/Fuzz%20and%20Overdrives/?action=view¤t=peachyfuzz.jpg

im wondering if it's not some kind of refresh thing on your browser.

so, how does it sound by the way?

[brian wenz]

Hello Hello Casey--
       I've been wondering about those resistor values on the Peachy  [680K and 4.7 Meg]  and lately  someone who knows much more about these older RCA circuits swears that those values are incorrect, so I'm going to substitute some obvious values [680 ohm and 47K, etc....] to see what happens. As it sits now the Peachy doesn't sound bad, but it's more of a "one tranny" booster-type sound then a two-tranny circuit.
Here we go again....!
Brian.

[casey]

good luck to you....as far as i know, that schem. is the original one
that appeared in the Feb. 1968 popular electronics....

i hope your endeavor goes well.

keep us posted....

[brian wenz]

Hello Hello--
   Yeah, The schematic looks original to me, too, that's why I wish someone would tear this circuit apart and explain the theory in back of it.
Brian.

[casey]

Hello Hello--
   Yeah, The schematic looks original to me, too, that's why I wish someone would tear this circuit apart and explain the theory in back of it.
Brian.

mark hammer?  r.g. keen?  jack orman?

[brian wenz]

Hello Casey--
  I think alot of people are "done" with this thread!!
Brian