need help fixing a Morley PWB

K-Funk · #1 02-19-2008, 09:49 AM

OK, so I just got this really old Morley PWB a few months ago for $40 in a pawn shop. It's in mint aesthetic condition, but it has a couple internal issues:

1)The boost doesn't work. I think the switch may be broken, because when I push it, it doesn't click or do anything.

2)More importantly, the wah is out of calibration. IE, it wahs both ways, and the "neutral" spot is about two or so inches before the heel hits the plate. This is a problem because it limits range and messes with the volume function when the wah is turned off.

Any ideas as to how I can fix these issues myself, before taking it in for repair? thanks!

bongomania · #2 02-19-2008, 09:55 AM

The switch should be easy enough, just get a replacement switch and bung it in. Just be sure you have the correct type of switch. The wah sweep is optical IIRC, it uses a lightbulb shining through a strip of plastic which has a gradient of trasparent to black opaque. You adjust the calibration by adjusting the position of the plastic strip and the position of the lightbulb.

niftydog · #3 02-19-2008, 03:03 PM

How old is "really old"? Is it chrome or black?

JanusZarate · #4 02-19-2008, 03:43 PM

Quote:

Originally Posted by niftydog

How old is "really old"? Is it chrome or black?

There is no black PWB. Only chrome.

I'm actually confused about the "calibration" comment... it's not supposed to be "neutral" when fully toe-up. A middle setting is as close as you'll get to "neutral" when it's on... but the use of that term is quite a stretch.

Toe-up, it's deep, rumbly, grunty. Toe-down, it's bright as heck.

niftydog · #5 02-19-2008, 05:28 PM

I read it more like the "neutral" point was just where the filter sweep starts over again - the OP said it wahs in both directions. That was a terrible description of what's in my head... but Boo might understand me!

To the OP - this wah mechanisim is mechanical and easy to understand - just pop it open and move the treadle and you'll soon see what's gone wrong. You'll see light bulb, a fabric flap connected to the treadle, and a small component called a light dependent resistor (LDR or photoresistor) underneath a cowling. When the treadle is fully heel down, the fabric flap should completely cover the cowling, leaving the LDR in complete darkness. When it's toe down, the flap should expose the LDR to the light from the bulb.

A bit of gaffa tape might be all you'll need to fix this.

K-Funk · #6 02-19-2008, 10:32 PM

sorry.... by neutral I meant the lowest, grumbly, cut-high sound possible. Where the heel is all the way down. The problem is that the wah "wahs" both backwards and forward. The low, grumbly sound is in the middle of the sweep. So instead of going:

"wwwwaaaahhhhh" from heel to toe,

it goes "hhhaawwwaaahhh" from heel to toe.

sorry if I explained it like a 6-year old

Sir Edward V · #7 02-19-2008, 11:02 PM

JanusZarate · #8 02-20-2008, 12:14 AM

Quote:

Originally Posted by niftydog

That was a terrible description of what's in my head... but Boo might understand me!

Yep. I speak canine. And feline, too.

Quote:

Originally Posted by K-Funk

sorry if I explained it like a 6-year old

It makes perfect sense, actually! Sounds like an issue with the photoresistor's alignment and/or the black covering over it. It's a really easy fix.

On a side note... the fact that it took explaining it to me like a 6-year-old for me to get it happens to perturb my previous perception of my own intellect.

Pushead · #9 02-20-2008, 02:41 PM

MysticBoo, could you share your knowlegde about the vintage Morley?
I also have a PWB and I'm not satisfied with the sound of the pedal and with the fact the is working backwards (Toe Up - Treble sound).

So do you have some advices to take advantage of all the capabilities of the pedal?

JanusZarate · #10 02-20-2008, 02:49 PM

If it's working in reverse, you need to make some adjustments inside. It's been a while since I last owned a vintage Morley, but it's not difficult to adjust the footpedal's hinges (there should be a nut holding it together), the covering over the photoresistor (easily fixed with tape), or the photoresistor itself (bend gently with your hands to make it face the lightbulb directly, or bend it away slightly for a less bright tone). Just open it up and take a look inside.

Just to make sure everything else works... it should function as a volume pedal when the wah mode is off, and the Boost mode should add a ton of volume and a bit of mild overdrive. Hiss is to be expected on the high end.

Those of us who love the PWB tend to love it most when used after distortion.

If you don't like the way it actually sounds, I'd recommend selling it instead of modifying it. There are plenty of people who like it as-is.

niftydog · #11 02-20-2008, 04:00 PM

Trust us guys, it's easy as, the moment you open it and move the treadle you'll know what needs to be done. Just keep in mind that the photoresistor has to be in complete darkness when the heel's down and you'll be sweet.

Just do me a favour and unplug it from the wall socket before you open it!