Wah cry baby Help! Off board wiring for a 60's Jen .

[seagurt]

I am working on a pedal for a friend, its a 60's wah (was all original) but the thing gave up. The solder pads, and tracks were lifting, and trying to reflow solder to the points/applying silver trace, only resulted in smoke and an awful smell.

He asked me to reboard the whole unit, so I bought a Tonepad wah PCB. I have not been able to find any info on how to wire the effect for the fly leads and offboard wiring. I also have not been able to find a schematic.

When I tested, there was no signal going through at all. The only mod I made, was to add a DC jack.

Here is a link to a few pictures (I am aware that the transistors aren't in the sockets, I tested with them in of course). I would have posted them here, but I cant figure out how to resize the image so that it isn't the size of 4 screens...

http://imgur.com/CvSt7QJ
http://imgur.com/CVpOU8X
http://imgur.com/gPTolB1
http://imgur.com/awXF20S
http://imgur.com/wuBJ70w

If anyone knows how I can get this baby back up and running, I would be eternally grateful!

Thanks again guys/gals!

[thermionix]

I think in its original form, the Jen would have been pretty much the same as the early Crybaby, or Vox wahs:



Looks like the 82K was changed to 68K, as you have two of those on your board and no 82K.  Also looks like the Tonepad board has some extra parts; a 1M pulldown, and a filter cap and protection diode for power jack use.

I'm not familiar with the layout of the Tonepad PCB.  Do they have a wiring guide on their site?  I *think* you have a redundancy at the output, but I can't tell you how it should be done with that PCB.

[thermionix]

Do you get sound in bypass?  That should work even with the transistors out of the sockets.

For further reference, here's an actual Vox schematic from an early "Clyde McCoy" wah.  It has a couple different resistor values, and an error (says 68 instead of 68K on the input resistor).  Might help figure out the switching though.

[seagurt]

Normally I would expect the effect output to come from the pot, to the switch, then to the output jack, but I'm also used to true bypass switching (which I would highly recommend in your case BTW - you would need a new DPDT foot switch).

Thanks for the reply. I do have DPDT switches, So it would be easier to just wire up a DPDT in true bypass? I'll give that a go.

I *think* you have a redundancy at the output, but I can't tell you how it should be done with that PCB.

I'm sure you are right. I tried both options individually as well, then tried both to see if that changed anything signal path wise (though I knew better and tried anyway...).

Do you get sound in bypass?  That should work even with the transistors out of the sockets.

I'm 99% positive signal passes through on bypass, but I will check in the morning again, as I cant recall 100%.

Thanks for all the info!

[thermionix]

Okay, I've looked at Tonepad's documentation, and I think I have this figured out.

-Remove the short wire you have running between the pot and switch.  That connection is handled at the board now.

-The white wire you have coming from the PCB "out" should be disconnected from the output jack, and either extended or replaced with a longer wire.  Now connect the free end to the switch lug that used to have the short wire hooked to it.

I think that should get you rockin', assuming everything else is right, but yeah in the long run true bypass would be a great improvement for this wah.

[Edit:  Sorry for all the edits!]

[thermionix]

I should add, I can't be sure of that switch and which lug is which, unless I had it here to beep out.  I'm guessing you're using it pretty much as it was originally.

Also, are you getting +9V at the board?

[seagurt]

-Remove the short wire you have running between the pot and switch.  That connection is handled at the board now.

-The white wire you have coming from the PCB "out" should be disconnected from the output jack, and either extended or replaced with a longer wire.  Now connect the free end to the switch lug that used to have the short wire hooked to it.

I think that should get you rockin', assuming everything else is right, but yeah in the long run true bypass would be a great improvement for this wah.

I followed your directions, and I am still not getting a signal through with the changes.

Here is a pic of the changes.

...Also, are you getting +9V at the board?

Yes I am getting +9.6V on the board.

Do you get sound in bypass?  That should work even with the transistors out of the sockets.

Yes I am getting a signal in bypass.

Perhaps I should try the DPDT switch? Is there any particlar wiring setup for the DPDT on a wah? Or do I just apply the usual true bypass wiring? Anything to note (for example, it seems that the switch would have signal from the INPUT Tip (which is bridged to the PCB IN) and a signal out to the PCB OUT, as well as a lead to the OUTPUT tip.) is this right?

Thanks again for all the suggestions and comments. She will live again!

[thermionix]

I thought about it more last night after posting, and I figured there would still be an issue.  Though the output wiring change you did is correct, it should have had sound before, just always on I think.

The foot switch you have in there is confusing to me. The job calls for a SPDT, which is a 3-lug switch usually.  That one has 4 lugs, but two of them are wired together.  Like I said before, I just can't tell without checking it out with a meter.  Switching to DPDT true bypass would clear that up, and also keep the pedal from being a tone sucker when in bypass.  You have a pulldown resistor already, so the simple, common TB wiring would be just fine.

But it should still get sound through as is.  You can try a jumper wire across switch lugs and see if that makes anything happen.  The fact that you get sound in bypass makes me inclined to think that you wired the switch correctly though.

But before all of that...what kind of transistors are you using?  Are you sure you have the pinout correct?

[duck_arse]

that type of switch is tricky to name, poles/throws wise. it has two contacts each end, and throws an internal shorting-bar from one end to the other when stomped. so it is two single pole single throws, but in opposition.

they are most often seen with one lug from each end connected together, and used as the common, thus making a SPDT.

[thermionix]

In that case seems it's wired correctly.

Waiting for transistor info.

[seagurt]

In that case seems it's wired correctly.

Waiting for transistor info.

I am using 2N532a transistors.
The circuit called for MPSA18's but apparently the 2N532a's are a substitute. The pinout appears to be correct from what I can see.

[thermionix]

Only info I could find with Google says 2N532 is a Ge PNP transistor. 

http://alltransistors.com/transistor.php?transistor=4742

PNPs will not work!  Almost any common Si NPN will work in a wah.

[seagurt]

Only info I could find with Google says 2N532 is a Ge PNP transistor. 

http://alltransistors.com/transistor.php?transistor=4742

PNPs will not work!  Almost any common Si NPN will work in a wah.

I placed an order for some MPSA18's.

I will try and see if I have any silicon NPN's lying around. Does the HFE gain make a difference? Should I avoid class A or B transistors (by class I mean the letter at the end that denotes HFE level)?

Thanks again!

[thermionix]

Some people probably prefer certain gain ranges, I've heard hFE ~400 mentioned here and there, but pretty much any NPN should let you know if your wah is working.  Nothing special about MPSA18s, but they'll do since you already ordered them.  In the meantime, if you find some NPNs lying around, plug 'em in and let us know what happens!

[seagurt]

Unfortunately I dont have any NPN transistors around. Seems like I will have to wait the month plus for it go get here. I will post again if they get here, and something is still amiss.

Thanks all for the info!

[thermionix]

Unfortunately I dont have any NPN transistors around. Seems like I will have to wait the month plus for it go get here. I will post again if they get here, and something is still amiss.

Thanks all for the info!

A month?  Ouch!  I'd be digging around for a broken radio or something to rob parts from.  NPNs are everywhere!

Well let us know even if it works.  Good luck!

[seagurt]

A month?  Ouch!  I'd be digging around for a broken radio or something to rob parts from.  NPNs are everywhere!

Well let us know even if it works.  Good luck!

I did indeed take apart a few radios, and even a few unused pedals, I couldn't find any transistors to fit the bill, but the MPSA18's came in the mail today (I ordered 10, and got 25...?). 

I have come to a new problem, everything is wired up, except for the out on the pcb. I cant figure out where I am supposed to attach the out from the board.

Here is the wiring diagram I have used



And here are pics of the build/repair so far.






I had to solder the MPSA's to the sockets, as they had way too much room, and I dont want them to move. Kinda defeats the purpose, but I did what I had to do to make it solid.

Almost there, I can feel it, and if for some reason it doesn't work, I will just come back here again, and ask those with superior knowledge.

Thanks again to all who replied, this is a special project for someone dear to me, and it will mean the world for him to have his tone back.

[thermionix]

The OUT from the board is the same as the short red one you now have between the pot and switch.  Remember you removed that one earlier?  To use both would be redundant.  Either way should work.  Fire it up, I think you're done!

[seagurt]

The OUT from the board is the same as the short red one you now have between the pot and switch.  Remember you removed that one earlier?  To use both would be redundant.  Either way should work.  Fire it up, I think you're done!

It worked. I was sure I had something missing.

Thanks again for your expertise. It is greatly appreciated, off to deliver this to my friend now, thanks from him as well!

Cheers!

[thermionix]

Awesome, glad you got it going!