Dunlop wah DEBUG re-post with images

Started by philbinator1, January 19, 2010, 04:34:04 PM

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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!  icon_redface
   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.    
Sorry for the re-post, thought I better provide some images..






cheers
phil
"Hows are we's?  We's in the f*cking middle of a dinners meal!  Dats hows we am!" - Skwisgaar Skwigelf