Mondo Morley Medicale: PWO Power Wah

What is it about these big, chrome, noise-making monstrosities of ’70s tech that I find so appealing? The answer is in the question, really. Just before Christmas, I couldn’t resist just getting the damn thing for myself: a Morley PWO Power Wah. eBay, you are a wicked temptress. 
Morley Power Wah Fuzz, but it was necessary to apply some salve. 
The first problem was the actual effect. It was doing something, but it was all wrong. The wah effected half way, then went silent, then effected opposite as the foot treadle was moved on its axis. I suspected immediately that it was the curtain that rolled over the light dependent resistor inside the pedal. These things were taped in place originally… thirty years ago. When I opened it up, it sure as shit was flapping about. I removed the flap.

You can see it’s just masking tape that’s supposed to be holding it all together. I marked where it was and simply taped the curtain back in place. Easy, peasy, nice and squeezy.
If you have everything in place, the foot pedal will roll the curtain over the LDR and block the light from the power indicator as it’s pressed towards the heel. You can adjust the LDR slightly to allow more light on it, carefully so as to not break the leads. The curtain can also be adjusted with the nut attaching it to the foot pedal. 

The wah was working well now. In fact, really well. I like the PWO wah sound a lot more than the already incredible wah sweep on the Power Wah Fuzz. It has a richer body to it, allowing a more full range of frequency to come through. I also like the fact that this is one of the rarer Morley pedals that doesn’t double as a volume pedal, like the Wah-Volume WVO. On the PWO, the treadle can be left at any angle and engaged into wah mode. On the WVO, you’re subject to where the treadle is set for volume when you want to engage the wah.

Next up, I tackled the aesthetics. Hey, if you’re gonna have a huge, chrome box taking up stage real estate, it better look sharp. This guy had a lot of dimpling in the chrome finish that led to big rust spots. The spots look worse than they are as oxidization spreads. The best thing to do is get rid of as much as you can with a fine 000 grade steel wool pad rub down.

Pretty soon, I had polish you could see your reflection in. If it ain’t chrome, it ain’t got the tone. The dimpling in the chrome is still there and will cause problems with rust in the future. Polishing is no longer for vanity, it’s to keep this thing from rotting. 

The bottom of the pedal was pretty fucked. The rubber feet were gone and it had velcro from being on someone’s pedal board. Nasty masking tape was also on there. It all had to go. This is where A.D.D. is a blessing and curse… does the bottom of the pedal really matter?

I had to get a little more aggressive on this part. The bottom is made of sheet metal and not chrome plated. It requires sandpaper to polish. I started with a 320 grit and moved up to 600 and ended with 1200 for as fine a polish as I could get. I replaced the feet with some generic sticky-backed rubber feet available at Radio Shack. They are really close to the originals.

For once, the 387 power indicator bulb was actually in-tact and working. This is usually blown and folks think their pedal is dead. As a matter of course, I like to tape in a spare bulb for future generations. I believe the children are our future. Hey, that’s got a nice ring to it. I should write that down, or something.

Something about these old guys made in the ’70s… sure they take a little more massaging, but they are able to keep on ticking and kickin’ ass. Oh, and the pedals from that era keep working, too.

Doktor Wahss Sewage

6 thoughts on “Mondo Morley Medicale: PWO Power Wah

  1. I have a Sumerian-era Morley WVO wah-volume pedal and the volume effect was no longer completely fading out like it should when the pedal was in the "up" position. As the pedal was "rolled back", the volume would fade out then fade back in when it should have been completely silent. (This is most annoying when using the pedal with a delay to get those classic David Gilmore/Steve Howe swells.) After seeing your post regarding the PWO, I cracked open my – I hate to brag – nearly mint WVO and sure enough the masking tape had worn out and torn thus causing the curtain to fall on "my show". I guess the life expectancy of Morley's masking tape is thirty years. Thank you for helping to restore what is an essential part of my rig with no out-of-pocket expense.

  2. Hi there!

    I have recently bought myself a PWB.

    There are 2 LDRs under the curtain. Which 1 does what?

    The middle 1 is the smallest and is black(ish). This 1 is laying down, but when i cut the light to this sensor, nothing happens.
    The 1 on he left side is the larger 1 (white). This 1 is facing towards the bulb. When i cut of the light on this one, the wah kicks in, or out. (anyway, it works).

    Can you please tell me what the differences between the 2 are? And should that little sensor be working as well as a LDR?


    Greetings Erik

    1. The smaller sensor should control the amount of volume boost when you engage the "BOOST" foot switch on the left. If you're not getting any boost, try (carefully) to readjust the LDR so it's in the same light path as the wah LDR. If it still doesn't work, well, something else is wrong.

  3. I’ve been given a PWO.
    the power cord insolation is coming apart. I opened the unit to try to replace the power cord, but found a plastic guard that protects it from pulling the cord out from the power supply. How do I replace the cord without breaking this?
    Also, the wah is very noisy on the treble side. Any suggestions?
    Many thanks in advance

    1. I think you’re talking about the cord “strain relief,” the round plastic circle the cord goes through from the outside into the chassis. Bad news is there’s no way to remove it… you have to cut it out. Good news is you can buy these in most hardware stores in the electronics section or order them online. Place a new one on your new cord, solder the cord in, snap the strain relief back into place. Done.

      As for the noise… are you talking about static? Or that it’s too trebly? It shouldn’t have static; the whole basis of the photoresistor and curtain is to remove that. If it’s got too much treble, you could try a few things, like messing with the resistor and capacitor values towards the output to create more of a low-pass filter.

Leave a Reply

Your email address will not be published. Required fields are marked *