SparkleDrive Clone problem

[alderbody]

I built a SparkleDrive Clone and it worked fine in the beginning...

suddenly it started developing crackling background noises, and i assumed it must have been the filter electros (33uF) in the supply/reference voltage section.

I replaced them and after that there is no sound at all...
There's only some huge crackles when i turn the Volume pot near its lowest setting...

I measured the reference voltage which should be around 4.5V with a 9V supply, and it was around 7.57V!

Does this ring any bells to anyone?

I will try replacing the input transistor (a CV7112) and the chips (JRC4558D and NE5532P) and see what happens...

Any help would be much appreciated...

[MadMac]

Sounds like a dirty pot.  Change the pot first.

[alderbody]

Sounds like a dirty pot.  Change the pot first.

...the pot is brand new!

i thought about it being faulty, but it worked fine yesterday when i first tried the pedal.

it's rather unlikely, but i'll give it a try anyway...

[mojo_hand]

I measured the reference voltage which should be around 4.5V with a 9V supply, and it was around 7.57V!

Have you tried re-setting the trim pot to 4.5v to see what happens?  Because it's not going to be making any desirable sounds when it's at 7.6 volts, regardless of what else may or may not be wrong with it...

[alderbody]

Have you tried re-setting the trim pot to 4.5v to see what happens?  Because it's not going to be making any desirable sounds when it's at 7.6 volts, regardless of what else may or may not be wrong with it...

trimpot?  ...what trimpot? 

there's no trimpot in the schematic i used.

btw, last night i replaced the transistor and both chips, but still the same. No output!

I think i'll re-build the voltage divider circuit, but then again it's quite unlikely that a resistor (1% metal film) has gone bad in ..two days.
The caps have already been replaced twice. Could it be the reverse polarity protection diode?  I don't think so.

Maybe there's some unwanted contact somewhere (it's a perfboard build).

I guess there's still a lot to be done...