Officially Lost

[duffrey]

I am still working on this rangemaster of mine.  I finally have the tranny biased properly, and everything appears to be working great, until I turn it on.  Even with the pot all the way up, my volume gets cut drastically.  The tranny I have is a Smallbear tested one, could I have blown it?  How would I know?  
I have built infinitly more complicated circuits than this, and this is really getting to me.  
What else could it be?

Lost and confused.

Jeff

[Jered]

Post the voltages you have at the B, C, & E of your transistor and we can probably get  an idea of your problem.
 Jered

[duffrey]

Hey Jered
Here are the voltages as measured from the power supply to:

E  -6.43
C  -7.2
B  -6.57

I'm also using trim pots to bias it.  So to get different resistor values is easy, but no matter where I place them hasn't seemed to help.
Thanks for your help

Jeff

[Jered]

Hey Jeff,
     Go to    http://www.geofex.com     click on the "schematics and more" link, scroll down a bit and you will see the Dallas Arbiter Rangemaster write up that RG did. RG goes over every part in detail and troubleshooting. Its a wealth of Rangemaster/treble booster  info.
  Good luck, let us know how it turns out.
  Jered

[smoguzbenjamin]

The tranny voltages look kinda wierd though... :?

[duffrey]

Hey guys thanks for the replies.
I am now convinced that the tranny is ok, and biased well.  
Voltages as measured from ground to:

E  3.22
B  3.03
C  1.88

In R.G's debugging page it says that the greatest difference in voltage should be between the C and E of at least 1V which it is, and then the B should fall in the middle with in 0.0-0.3V which it is.  
So I gues it has to be something else.  
Can you short poly film cap?  and if so, could you still get signal through it if you did?  

Jeff

[smoguzbenjamin]

Short it? I guess the signal would just bypass the cap completely then... Nothing can really go wrong with the cap. :?

[Paul Perry (Frostwave)]

My money is on a wrong resistor value.

[duffrey]

If that is the case there is really only one resistor iit could be.
I have pull down resistors (1M each) which shouldn't be doing anything out of the ordinary.
The the resistors for biasing the tranny are trim pots, so those I can set and leave according to the voltages on the tranny, so if the tranny is coming up right, then it shouldn't be those.  Am I right?
So the only other resistor in the cicuit would be the one from the B of the tranny to the other side of the pot.  The schematic I am using calls for a 220K, which is different than every other rangemaster schematic that I have come across, but this version is also a negative ground one.
What should that value be then?  Higher or lower?
I'm just about willing to try anything at this point.  I'd rather spend my time basking in rangemaster tone, than contemplating about rangemaster cicuits.  
Thanks guys

Jeff

[petemoore]

with a 9v battery I think the collector is supposed to be biased at around 7v for the R sound'.
 These readings look like the E/C got inverted.
 The emitter is higher than the collector...needs looked at.
 I use 3906 for R prelim testing and debugs, then once I get it to where it looks like I can control bias, and get things sorta within range, I get the Transistor I want to use out. That's just me...it's too easy to not get the pinout right...well these days...but you never know when you're going to hook up a NEg ground out of habit or something...
 My guess is with a pinout problem or a miswired R.

[duffrey]

Thanks for the reply
I have tried reversing the C and E on the tranny, and get similar results.  Still very low out put.  
I have even replaced the output cap just to make sure.  
I wish I had bins of parts here, but to get parts for me is a pain.  I live in a small town and to get to a decent parts store is a 45m drive one way.  Well I might have to bite the bullet and get another tranny to try.  

Jeff

[Lonehdrider]

Is it on a PC board? Just curious, another post mentioned (and I do it too now just because it was a good idea) TINY pieces of copper shorting out a trace seen only under a magnifying glass. Course if its on a strip like the original or perf boarded then I'll pull the starwars mind trick on you and 'you didn't read this'.

Regards,

Lone

[Gearbuilder]

Hi ,
What is the Hfe of your trannys ?Germ are not consistent so it's mossible that a low gain reduces the output ,no?

Bruno

[duffrey]

It is on a PCB, and I have looked very carefully, though maybe not under high enough magnification, for little traces.
The Hfe of the tranny was between 85 and 90, don't remember right off, but I don't think that is the case.  
Thanks for all the help guys.  I'll get this thing going yet.  

Jeff

[duffrey]

Ok, so now here's what I have just done.  
I tried switching the E and C of the tranny, like Peter suggested, then rebiased, and the thing actually started amplifying less than before.  So that's not it.  
It is built on a PCB so I found a really high powered magnifying lens, and then scratched around every trace on the PCB (after all it is a small board), to no avail.
I have replaced the only fixed resistor with a fresh one, and made sure that the variavble ones I am using work, and are wired right.  
I have noticed something strange though.  For every pin out that I have found for the tranny I have, the C and E are reversed from the one I have (indicated by the tab on the case)  But switching them around didn't help either.
Maybe I should just start over from scratch.   :cry:

Jeff

[brian wenz]

Hello Hello Duffrey--
   What schematic are you using??   Any germ Rangemaster-type circuit should  have 470K and 68K  [or close to it] in there.   The values need to be tweaked a bit for each tranny.  Also, the 4.7K or 3.9K  [off the emitter ] might need some adjusting.
Brian.

[duffrey]

Hey Brian
I am using Robert Keeley's design which he calls the Java Boost.  It is a negative ground version.  So he has adjusted a few values.
The 68k and the 3k9 values in the normal positive ground version are still there, but are replaced with trimmer pots so that once you have biased your tranny you don't have to go to the "closest" fixed value resistor thowing out your bias slightly.  
The 470K resistor has been replaced with a 220K.
Then it looks like the only other thing he has done is added a diode on the power supply, which should be there anyway I think, and he has switched the tranny around so that the emmiter is on the 10K pot side of things, vs. the 3K9 side.  
He still uses the Mullard OC44, which is a pnp, and I am trying to use the tested pnp from smallbear, so there should be no real difference right?  As far as functionality I mean.
In either case the base should be connected to the input from the guitar right?  
Sorry I'm still faily new to this pedal building scene, so I'm still ignorant of some basic things.  

Jeff

[brian wenz]

Hello Hello--
   I've had to adjust the bias differently on every Rangemaster-type pedal......changing the resistor values to match the tranny used.  
Yeah, the input goes to the input cap, [.005 or .0068] and then to the base.
I've only built pos. ground versions.....keeps it simple!
One thing I've never had to do is drop the 470K to 220K.
I've used lots of different germ trannys and with some res. value changes they all came out great.....I'm curious as to what  will solve your problem!
Brian.

[Marcos - Munky]

Now I remember. Some time ago, when the Java Boost schematic was posted, some guys said that the schematic need some work, because it won't work if you build it like in the schematic.

[duffrey]

Hey Marcos.
So I'm not crazy then?  
Do you remember what needed changing?
Thanks.  

Jeff