Old CryBaby wah pedal nnot "wah-ing"

[Helmholtz]

My old Vox Wah has exactly the same board and inductor. Measuring across the 33k resistor I get 36R. Out of circuit the inductor would measure the same as
the parallel 33k resistor lowers total resistance by only 0.04R.

So if you measure 30k across the resistor, it's either not connected to the inductor at both ends or the inductor is open (broken magnet wire).

[Fred G.]

Yes, I've hopefully been following the guidelines you're providing carefully. I can't help but always keep drifting back to the inductor being faulty, based on the advice I've been getting. The pedal is "working" fine when switched in, except it just refuses to "wah". I feel like I have done every other means of due diligence (jeez, I cleaned and re-soldered EVERY dang contact under the board, fer Chrissake), other than to replace the inductor. Wouldn't a good inductor give a positive continuity reading, though (a beep)?

As always, thank you for sticking with me on my questions. BTW, I fixed that solid-state Fender Yale ;-)

[vintagekiki]

If you measure a 33k resistor and instead of a small resistance you get a value of the order of 30k, there is a high probability that something is wrong with the 0.5H coil.
Careful on the pins of the 0.5H coil check the resistance.

[Fred G.]

OK...I have the board loose. I reflowed all the solder joints - many looked cold, lifted traces, a mess. This pedal still just will not "wah". When I read across the 33k resistor, I got about 30k. No change, there. I'm reading continuity across the inductor, but - wouldn't this indicate that the coil is OK?

[g1]

The insulating (fiber) washer is there to prevent any traces from being shorted to ground via the nut/bolt. It should be put back in during re-assembly.

[vintagekiki]

Perfect. Now compare your PCB ...

https://images.reverb.com/image/upload/s--q6No-dwW--/f_auto,t_large/v1574631407/p7voxkmutupvctit35mk.jpg

1)

[Fred G.]

SUCCESS !!!!! I got the dang circuit card free !!

I held a hot soldering iron to the protruding bolt bottom while tugging with a pair of mini-pliers, and it came right off after a few seconds. I got a massive does of varnish smoke in the eyes, though, and boy did THAT burn for a couple of seconds...it turned out there was a fiber washer stuck to the bottom of the board, between the nut and board.

Now I can get to a serious testing and going-over of this thing. Already seeing a couple cold-looking solder joints and some trace lifting. Thanks for hanging with me fellas! Gotta knock this one out, there's a vintage Supro coming in from the local Mom n' Pop music store.

[Mick Bailey]

I question the need to dismantle the wah in order to establish the fault. You should be able to measure the DC voltages and intercept the signal path at any point from the component side - sometimes not on the component itself, but at the junction with another one. Those 'tropical fish' caps can go open and can be paralleled with a good cap to check - just hold it in position.

[Helmholtz]

As said earlier, first loosen the lower (battery side) nut before punching the axle out. Otherwise you might break one of the tensioning screws.

[Fred G.]

OK - would I just use a hammer and a punch and punch the axle out? Man, that makes me nervous about causing permanent damage! I'm going to look for the broken lead wire, and also try to free the front treadle bolt from the board by heating the bolt first. I'll need some direction if I have to knock out the treadle axle.

[vintagekiki]

To remove the treadle, you must break out axle that connects the treadle to the wah chassis.

[Helmholtz]

As the inductor pins the wire is attached to are accessible without removing the board: Inspect them with magnifying lens for a broken wire.

[Fred G.]

Fred G. please photo the bolt (screw) in close-up. To remove glue fom the bolt, try to carefully heat the bolt with a strong soldering iron to melt the glue.
The nut you see most likely holds a bolt attached to the wah chassis. White-ish adhesive on the nut, prevents the nut from loosening.

That is exactly what I have been describing for three pages now. The bolt cannot be accessed to unscrew it. The nut cannot be accessed to turn it. It is cemented to the bottom of the board. The access is so constrained that tools cannot be inserted to do anything. THAT is the problem, and, yes, as I have said repeatedly, the nut holds a bolt coming through the wah chassis (I've referred to it as the "front treadle strap bolt"), and it can't be accessed without removing the treadle, as far as I can tell. I'm trying to find a solution to that, I sure as hell can't visualize one. I can try super-heating the bolt and see if it melts the adhesive, otherwise, the treadle has to come off, or - this pedal will make a nice bookend. It's driving me mad with frustration!

Thanks!

[vintagekiki]

This inductor is definitely worth repairing.

This requires removing the PCB from the wah chassis, remove inductor, reparing inductor ...

And looking under the circuit board with a dental mirror, I see a nut that appears to be cemented to the board, looks like a thick pad of a white-ish adhesive between the nut and board.

Fred G. please photo the bolt (screw) in close-up. To remove glue fom the bolt, try to carefully heat the bolt with a strong soldering iron to melt the glue.
The nut you see most likely holds a bolt attached to the wah chassis. White-ish adhesive on the nut, prevents the nut from loosening.

[Helmholtz]

Measuring across the 33k resistor connected to the inductor yielded a value of 30k, within 10% tolerance. This would indicate the inductor is bad?

Looks like an open inductor. Should measure around 36R.
It might be possible to repair it by resoldering the coil wires connecting to the 2 pins accessible from the top.
That inductor is definitely worth repairing.