70s Morley Power/Wah/Boost- What are the internal trimpots for?

sunbeast · #1 08-27-2008, 06:44 PM

Anybody know anything about the old Power Wah Boost pedals like Cliff Burton used to use?

There are 2 internal trim pots that I can't figure out for the life of me- any help would be greatly appreciated!

Thanks,
Karl

B.C. · #2 08-27-2008, 06:55 PM

Quote:

Originally Posted by sunbeast

Anybody know anything about the old Power Wah Boost pedals like Cliff Burton used to use?

There are 2 internal trim pots that I can't figure out for the life of me- any help would be greatly appreciated!

Thanks,
Karl

I'm not sure, but most likely one is for gain.

niftydog · #3 08-27-2008, 07:44 PM

FYI the circuit diagram is freely downloadable from the Morley site.

Looks to me like they are involved in trimming the bias for two transistors, one in the boost section and one in the wah section.

niftydog · #4 08-27-2008, 07:48 PM

Worth mentioning that there are several dangerous voltage sources inside these old Morleys.

Mains power is incredibly dangerous, and in old gear such as these the safety standards are lacking compared to modern equipment.

Also, there's a 55VDC source which is completely unprotected and could give you a very nasty boot if you get across it.

So basically, be bloody careful if you are tinkering!!

sunbeast · #5 08-30-2008, 02:40 AM

Any other Power/Wah/Boost owners out there that know the magic?

Thanks,
Karl

sunbeast · #6 03-19-2009, 08:24 PM

Still wondering about these internal trim knobs...anyone have any ideas?
There is a picture in this thread where one of the 2 wheel-knobs is visible (the wheel in the upper part of the picture):
Morley PWB Repair

I have very limited understanding of how a wah pedal works, so the schematic in itself just adds to my confusion (but thanks for the tip!). I should add that when moving them, each will cut sound completely at the extremes, and in between them I can't really tell what (if anything) is happening...

Thanks,
Karl

Basstovsky · #7 03-19-2009, 09:50 PM

When I fixed the flap in mine, I tried tweaking them, no really noticeable response, but I don't think I tried all 3 modes (wah, volume, boost) in all combinations so I can't be too sure. One seemed to adjust the sensitivity of the sweep a little, but it may have been altered movement of the flap, mine isn't in the best condition and could vary from other people's.

bovine mind · #8 03-20-2009, 12:30 PM

i have the power wah fuzz version, one terrifying, sweet pedal. i've wished i could tweak it to contain more of the bass note when using fuzz with it like some of the more modern wahs that leave the lower freq's alone. still, it's just such a great vintage aggressive wah sound that i won't get rid of it.