Ibanez PT9 phaser - the phasing doesn't work

[yeeshkul]

The sound goes through, however:
- the speed pot doesn't work
- the range pot does work.
- I have no schematics for it.

There are 3 chips 3403AD inside and 8 elyte caps, that seems to be very low voltage ones (probably to fit in).
Where shall i start looking? Shall i change the caps first?

[anchovie]

- I have no schematics for it.

You do now! http://uploadbox.com/files/9774041ddf/

[Mark Hammer]

First, verify that the LFO is actually producing a changing voltage.

[yeeshkul]

Guys thank you! The LFO is producing a changing voltage - i actually managed to get the phasing out of it by tweaking the two trimpots. Now i am tuning
it to the best sound. Which i don't know what it is supposed to be like .
Thank you for the schematics anchovie.

[yeeshkul]

I managed to make it work. The bias adjustment via VR101 trimpot was an ultra subtle job
(to get the Fig.B) and i can easily imagine this can be de-tuned just by dropping the pedal on the floor or kicking it.

However i am not sure with the feedback adjustment - i just don't understand the Fig.C.
What is the diamond shape around the phase diagram? Are those some sort of boundaries?
What i could see on my scope was just the oval, or something close to the Fig.B, but here the angle is
90 degr. from what i've got.

Any idea?

[Fender3D]

VR102 controls the amount of signal fed back to phase shifting stages.
You may set it just before auto oscillation starts (with feedback pot fully CW).

[Mark Hammer]

If I was working in a factory, alongside other people, setting the feedback trimpot by maxing the Feedback pot and adjusting the trimpot "until the howling stopped", would get old pretty quick.  The Lissajous patterns are basically so multiple people can make the adjustments silently, using a scope.

Since it's just the one pedal, unless you're making your adjustments at a daycare centre during nap-time, feel free to do it "the old-fashioned way".  Max the Feedback pot, and tweak the trimmer until the howling stops....or until its tolerable, if that's your pleasure. 

[yeeshkul]

Yeah i have done that that way in the end. But the squealing doesn't stop completely at some point - it seems to be mixed in and fades away slowly. Since i have no other unit to compare the sound i was gonna do it the nappy time way, haha.