Dunlop sw-95 wah pedal issues
« on: August 20, 2012, 11:44:00 AM »
Hi guys,
Apologies for my first post being an ask for help !

I am currently attempting a repair on a Dunlop Crybaby wah pedal. Model is the SW-95.
It's been a while since i've had to troubleshoot a pcb to this extent, usually there are nice black marks that are fairly obvious :)

The overview is, i'm currently tracing out the signal path using an audio probe....it goes to a tl072 opamp, and then turns to static. Albeit..static that matches my guitar strumming patterns. 
The opamp doesnt have a +18v vcc+, or a -18v vcc-.  The supply voltage is from a variable shop dc supply, so no battery issues.

The dc jack supply goes 18v to what looks like two resisters in parallel, and two 220uF caps which are grounded.  I think this is the supply filter circuit?  The input of the caps reads 1.5v, and this is heading to the vcc+ for the opamps.

I've replaced these 2 caps and no difference. That may or may not be expected by those who know far more than I :)



I've kinda made fixing this my new project, so would like to put some more hours and internet research into it, and drink a rightfully earned cup of tea when I achieve the victory that is the correct operation of the blue and red led's that this pedal has on board.

Im happy to take some decent pictures of the board and afore mentioned circuits if anyone has the time or interest to help guide me along.

As for myself, electronics is both a hobby and work. Im an avionics engineer by trade, but have not had much cause to go to pcb level apart from home washing machine repair etc. I have built my own CNC router from internet plans...so am happy enough to take things apart and duct-tape them back together :) Am happy enough soldering at this size circuitry and have all the relevant workshop bits.

Anyone interested in the hassle of trying to help ? :) 


Re: Dunlop sw-95 wah pedal issues
« Reply #1 on: August 20, 2012, 11:59:57 AM »
This is a rudimentary drawing of the supply circuit from memory...the pedal is in work atm..will get a proper picture when possible.


Re: Dunlop sw-95 wah pedal issues
« Reply #2 on: August 20, 2012, 12:02:37 PM »
Apologies if this is in the wrong section...perhaps it should have went in "the Lab" ?

okgb

Re: Dunlop sw-95 wah pedal issues
« Reply #3 on: October 02, 2012, 11:53:12 AM »
I would say , also try freestompbox.com or one of the other gtr related grps
GKB Audio / Greg Boboski

abechap024

Re: Dunlop sw-95 wah pedal issues
« Reply #4 on: October 02, 2012, 12:07:15 PM »
Try switching chips to new ones.
AC Sound - some DIY circuitboards


 

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