Wah complete debug sheet..hlp plz?

[philbinator1]

Hi guys,

I got told it's better to do an official debug than ask a million questions (well that was the subtext, and fair enough too)
so here it is..i've followed the layout of the debug page, so my info relates directly to the debug page's:

1/ Dunlop wah (no revision letter, maybe C or earlier, i read they didn't print the letters on those boards)

2/ http://www.freeinfosociety.com/electronics/schemview.php?id=350  is the schematic i've been working on, it
    seems as close to my wah as i can tell.

3/ I tried (with my noob eyes) to follow the schematic using an audio probe i built to see if all was in order; i had trouble
    with the probe cos i didn't know that all of the points didn't use audio and hence didn't make the noise i had going.
    I gave up on that and started with my tinkering...

4/ This is kinda embarrasing!  But...i recieved the wah and it needed the treadle tightened (done) and a power outage
    problem fixed.  I couldn't figure out what the hell was wrong so I replaced the switch and dc jack, re-soldered all the
    points, replaced all but one resistor (the old ones were 5% carbon film i think?) with 1% metal film resistors, replaced all
    caps (inc. the polarised ones, which I put with +v end towards higher voltage), replaced both transistors (man they
    gave me hell..I replaced the old 5117's with 2N4401's) and replaced the diode (the old one has 1N4739A 550 on it, put a
    1N4148 in it's place). 

    I should mention i did have two 2N4401's in the wrong pinout, I replaced them and put new ones in with the base and
    collector legs crossed over (but not touching).  AND I had one of the polarised caps  around the wrong way...but i tested
    them and they seemed ok.  maybe replace them anyway?  All replacements had the same value apart from the
    transistors.

5/ I'm pretty sure it's a negative ground circuit, the adaptor plug is the standard boss 2.1 mm -ve centre.

6/ When i try to wah with it, it sounds weak when compared to my red fasel GCB-535.  the actual wah effect is only about
    1/4 there.  And, when I hit the strings in heel-down position, it make a HORRIBLE crackling sound, not nice dist at all!
    And this is after all my 'upgrades'.  In fact it seemed to sound better before i started! 
    Also, i noticed halfway through replacing stuff that there was a severed trace at the loom pins, not liking that I
    soldered a resistor leg to the originating points (and yes, i did disconnect it and try the wah...no difference).

Here are my voltage readings (my batterie read 9.10 volts before i started):

Q1
C = 1.151 V
B = 0.743 V
E = 154.7 mV

Q2
C = 142.3 mV
B = 0.593 V
E = 94.8 mV
       
Diode (i don't know if it's a zener or not...?): 

K = 8.58 V
A = 0.0 V   


Phew!  Thats everything, i think...hope i've done everything right.  any help is so appreciated guys.     
If someone can advise me how to insert images, I have 3 gutshot photos ready to go as well!


cheers
phil

[petemoore]

Q1
C = 1.151 V
B = 0.743 V
E = 154.7 mV
  basic booster, should be biased with the collector having room to swing -/+.
  That would be around 1/2v. 
  Could be something with the orientation pinout [turned around?] or could be something is pulling the C toward Gnd. [that shouldn't be there] or something [that should] isn't pulling it toward V+

[philbinator1]

Hmm i did have the transistor pinouts wrong but thought i had them right.  how do i bias it differently?
i'm pretty new to this,if you could dumb the language down a bit that'd be great   

[jkokura]

I had a transistor problem this weekend also, and I found two datasheets with different pinouts. I'd double check the datasheets, and then consider every other option for what could be wrong.

I had another project with a backwards diode that was connecting my power to ground creating a power short. Turning the diode around sort of fixed the problem, but now the diode was blown. When I replaced the diode everything was fine.

Sometimes it's a really simple problem, and you just have to take your time and discover it. I've debugged almost every one of my 6 or 7 complete projects, and it's always something you wouldn't have thought of first. It's also the last thing you think of also, but that's just cause there's no need to think of more.

With everything you replaced, then I would guess that either something didn't get connected right, or that the trannies/diodes are orientated wrong. If it worked before, it can work again.

Jacob

[philbinator1]

I had a transistor problem this weekend also, and I found two datasheets with different pinouts. I'd double check the datasheets, and then consider every other option for what could be wrong.

I had another project with a backwards diode that was connecting my power to ground creating a power short. Turning the diode around sort of fixed the problem, but now the diode was blown. When I replaced the diode everything was fine.

Sometimes it's a really simple problem, and you just have to take your time and discover it. I've debugged almost every one of my 6 or 7 complete projects, and it's always something you wouldn't have thought of first. It's also the last thing you think of also, but that's just cause there's no need to think of more.

With everything you replaced, then I would guess that either something didn't get connected right, or that the trannies/diodes are orientated wrong. If it worked before, it can work again.

Jacob

thanks Jacob, i'll check the diode.  i'm gonna re-post this with pics, maybe that would help people to help me