Morley - Power Wah Fuzz [schematic]
Posted: 04 Jul 2018, 20:49
I did purchase a non-working Morley PWF stompbox from the 70'.
The seller told me the Fuzz part wasn't working anymore.
This post is a work in progress of my attempt to revive it.
Power
First things first : This pedal is 110 VAC powered, I'm in Europe and we're using 220V.
At the same time, I don't like having 220V at my feet with high powered vintage cables on my pedalboard.
If we take a look at the schematics : http://doktorsewage.com/wp-content/uplo ... /pwfes.pdf (found on http://doktorsewage.com/mondo-morley-me ... -wah-fuzz/ ) we can see that from the 110VAC 4 tensions are generated from the converted 28VAC:
- +60VDC (Wah Q2 collector)
- +7VDC (Fuzz)
- +20VDC (Wah Q5 collector)
- +25VDC (bulb power)
I did purchase a 220VAc to 28VDC adapter and then:
- drop the original 110V transformer
- drop CR1, CR2, C4 and C5
- connect the 28VDC + to R5 and R7
- connect the 28VDC - to the ground
After power up, bingo ! The light bulb did properly turned on.
I then decided to check tensions and then realized my mistake: How this circuit is supposed to upgrade my 28 VDC to 60V ?
Open question : Actually from the original 28VAC there is no diode bridge to convert it to DC, so are CR1, CR2, C4 and C5 acting as some kind of charge pump ?
Anyway I found the following tensions after my circuit upgrade:
- 60VDC : 25VDC
- 7VDC : 2,6VDC
- 20VDC : 8,7VDC
- 25VDC : 20VDC
So .. I'm quite far from what is expected, nevertheless I checked the PWF and surprise : The Volume effect (Wah and Fuzz off) is working just perfectly fine, The Wah effect works quite well too and the Fuzz is extremely light depending if the wah effect is turned on or not (from light to extremely light).
I guess that the Fuzz has some dead transistor or capacitor and the general low tensions have some impact on the circuit "stability"..
I'm thinking about setting up a complete power section based on the 28VDC external power supply and a batch of LM317 to generate expected tensions (and let use 28V for the expected 60V, I'll see that later.).
To be continued... !
The seller told me the Fuzz part wasn't working anymore.
This post is a work in progress of my attempt to revive it.
Power
First things first : This pedal is 110 VAC powered, I'm in Europe and we're using 220V.
At the same time, I don't like having 220V at my feet with high powered vintage cables on my pedalboard.
If we take a look at the schematics : http://doktorsewage.com/wp-content/uplo ... /pwfes.pdf (found on http://doktorsewage.com/mondo-morley-me ... -wah-fuzz/ ) we can see that from the 110VAC 4 tensions are generated from the converted 28VAC:
- +60VDC (Wah Q2 collector)
- +7VDC (Fuzz)
- +20VDC (Wah Q5 collector)
- +25VDC (bulb power)
I did purchase a 220VAc to 28VDC adapter and then:
- drop the original 110V transformer
- drop CR1, CR2, C4 and C5
- connect the 28VDC + to R5 and R7
- connect the 28VDC - to the ground
After power up, bingo ! The light bulb did properly turned on.
I then decided to check tensions and then realized my mistake: How this circuit is supposed to upgrade my 28 VDC to 60V ?
Open question : Actually from the original 28VAC there is no diode bridge to convert it to DC, so are CR1, CR2, C4 and C5 acting as some kind of charge pump ?
Anyway I found the following tensions after my circuit upgrade:
- 60VDC : 25VDC
- 7VDC : 2,6VDC
- 20VDC : 8,7VDC
- 25VDC : 20VDC
So .. I'm quite far from what is expected, nevertheless I checked the PWF and surprise : The Volume effect (Wah and Fuzz off) is working just perfectly fine, The Wah effect works quite well too and the Fuzz is extremely light depending if the wah effect is turned on or not (from light to extremely light).
I guess that the Fuzz has some dead transistor or capacitor and the general low tensions have some impact on the circuit "stability"..
I'm thinking about setting up a complete power section based on the 28VDC external power supply and a batch of LM317 to generate expected tensions (and let use 28V for the expected 60V, I'll see that later.).
To be continued... !