Electric Mistress with asymmetrical sweep (Puretube?)

[Arno van der Heijden]

Some time ago I picked up a broken Electric Mistress from Ebay and fixed it. It sounds great on some settings, but the LFO has a weird asymmetrical sweep.
It can be heard on this sample:

www.student.tue.nl/T/A.C.v.d.Heijden/Mistress.wav

How can I fix this? It's this version of the Mistress (schematic contains some errors):
http://www.fortunecity.com/tinpan/humperdinck/223/ehmist.gif

I was suggested that this could be caused by the string of transistors on the base of the 2n5087, but these seems to have the right values. I had to replace the SAD1024 and some opamps because they were fried, but I didn't replace the 4014 or the 339 so maybe it has something to do with that?

BTW, does anybody know how I can get a slight increase in volume?

[Lonestarjohnny]

Hey Arno, The Tube's on Vacation.
Johnny

[Arno van der Heijden]

bump

[Paul Perry (Frostwave)]

Maybe the electros around the LFO??

[puretube]

Guess this is Howard Davis territory - I`m absolutely not familiar with this topology - now on with vacation - sorry -  

[Arno van der Heijden]

Maybe the electros around the LFO??

Is there a way to test them in-circuit?

[moosapotamus]

http://howard.davis2.home.att.net/  

~ Charlie

[Paul Perry (Frostwave)]

Is there a way to test them in-circuit?

Not really, you casn test if an electrolytic is dried out by just putting a new one in parallel across it, but if the electrolytic has gone leaky then all you can do is desolder one end & put another across in place. I'm hoping that the bipolar has gone bad, if it leaks in one direction that is a source of asymmetry, possibly. I've had "weird LFO" probs from leaky caps in other circuits, anyhow.

[ErikMiller]

I'm fixing one of these for a client right now, and its LFO isn't oscillating.

I checked the caps in that section and they look good, so later this evening I'm going to swap out the 4013 and 339.

For a while I thought that since the delay chip is getting its clock, the 4013 must be good, but apparently they use half of the 4013 in the LFO, and half of the 4013 may be dead.

In the US, the 4013 and 339 are Radio Shack (easiest possible to obtain) stocked chips, so it's easy to shotgun those out; don't know about where you are.