Colorsound Fuzz Phazer issues (schem inside)

Started by disorder, December 14, 2019, 07:36:35 PM

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disorder

I got one of these bad boys in a trade, and I couldn't find a schematic for it online so I traced it myself. The unit has two issues, first is real weak phasing the second is bad radio interference and idle hiss/crackle especially when the fuzz is engaged.

Schematic: https://imgur.com/a/Wo5MLLi

It seems to be a manually controlled phaser (the dual gang pot that you control with your foot modulates two phaser circuit stages) with a fuzz circuit you can tack on with the push of a switch.

I have two questions about this circuit. First, when I took the pot out to test it, the two gangs are pretty mismatched. It's a 100k linear dual pot, I measured one gang max resistance as 180k and the other as 140k. So not only are the two gangs very mismatched but the are nearly 50-100% out of spec. Based on the schematic should the two pots be matched in a way that FETs would be matched for a Phase90 circuit?

Second, assuming I checked all ground connections, is it safe to assume the fuzz circuit in this is so high gain that radio station interference might be inevitable? Could I take on a cap to ground at the fuzz circuit input?

duck_arse

not terribly helpful, but from your dia, it looks like "a" fuzz face and a pair of magnavibe-type stages - really just phase splttters with the ldr/vdr replaced w/ pots. the mismatch between the stages shouldn't really be a problem if the pot is ok, but it looks very much like a not-for-wah type of pot from googoo photos.

is the base bias divider really 4k7 over 1M?
don't make me draw another line.

cushychicken

Heya - WAY late to the party here, but I'd be interested in the schematic trace of that Solasound Fuzz Phaser if you still have it. The imgur link no longer works.

bms19

Quote from: disorder on December 14, 2019, 07:36:35 PM
I got one of these bad boys in a trade, and I couldn't find a schematic for it online so I traced it myself. The unit has two issues, first is real weak phasing the second is bad radio interference and idle hiss/crackle especially when the fuzz is engaged.

Schematic: https://imgur.com/a/Wo5MLLi

It seems to be a manually controlled phaser (the dual gang pot that you control with your foot modulates two phaser circuit stages) with a fuzz circuit you can tack on with the push of a switch.

I have two questions about this circuit. First, when I took the pot out to test it, the two gangs are pretty mismatched. It's a 100k linear dual pot, I measured one gang max resistance as 180k and the other as 140k. So not only are the two gangs very mismatched but the are nearly 50-100% out of spec. Based on the schematic should the two pots be matched in a way that FETs would be matched for a Phase90 circuit?

Second, assuming I checked all ground connections, is it safe to assume the fuzz circuit in this is so high gain that radio station interference might be inevitable? Could I take on a cap to ground at the fuzz circuit input?
can you repost schematic?
Cheers
Ben