My Tonepad Phase 90 works but whats wrong with it? Help Please. Sound clip insid

[jimmybjj]

I have a all stock no mods board. Everything seems to work correctly but the sweep is terrible compared to a stock unit (or any unit i've heard on youtube) I have used the JFET match and tried several sets to no avail. The current set all read -1.93vgs. I have tried the 5.1v and 5.6v zeners, no help. What can I try, don't know how to fix a pedal than isn't broke  I have adjust the trimmer(multi turn unit) and it doesn't seem to effect the sweep. Both extremes of the trimmer have no phasing while the middle third or so only seems to emphasize different frequencies. I have turned it very slowly.

https://docs.google.com/leaf?id=0B5wdPNdaw6kMNzQzZmI5MGEtNjBiZS00N2Q2LWFjYzUtODQ3NzQyODkxMTcw&hl=en

[Thomeeque]

https://docs.google.com/leaf?id=0B5wdPNdaw6kMNzQzZmI5MGEtNjBiZS00N2Q2LWFjYzUtODQ3NzQyODkxMTcw&hl=en

"Sorry, the page (or document) you have requested is not available."

If you don't know how to make it work or have no other place where to upload the soundclip, use http://sendspace.com - it will stay there just for few weeks, but it could be enough.. T.

[jimmybjj]

https://docs.google.com/leaf?id=0B5wdPNdaw6kMNzQzZmI5MGEtNjBiZS00N2Q2LWFjYzUtODQ3NzQyODkxMTcw&hl=en

"Sorry, the page (or document) you have requested is not available."

If you don't know how to make it work or have no other place where to upload the soundclip, use http://sendspace.com - it will stay there just for few weeks, but it could be enough.. T.

Thanks, I didn't realize the link didn't work. I will try and update it tonight.

https://docs.google.com/leaf?id=0B5wdPNdaw6kMNzQzZmI5MGEtNjBiZS00N2Q2LWFjYzUtODQ3NzQyODkxMTcw&sort=name&layout=list&num=50

If that one still doesn't work i tried to sendspace

http://www.sendspace.com/file/nomlfo

[Thomeeque]

 Now google docs link works.

Sounds to me like very shallow voltage sweep at the FET gates.



You should double-check values of encircled components. Purple ones would alter depth of output voltage swing of LFO itself*, blue ones would alter ratio of swing between LFO out and FET gates.

Good luck, T.

*Healthy LFO set to the slowest rate should have cca 8sec period and voltage swing slightly above 2V at it's output (at slowest rate you can measure it even by DMM - measure the lowest and highest volage, it should be cca V_ref - 1V to V_ref + 1V).

[jimmybjj]

I did find one value out of wack. the 3.9m was a 2.2m for some reason. I won't be able to test it and do more work on it until the weekend. do you thing the 3.9m was the problem? Thanks for your help by the way, i really appreciate you taking the time.

[Thomeeque]

I did find one value out of wack. the 3.9m was a 2.2m for some reason. I won't be able to test it and do more work on it until the weekend. do you thing the 3.9m was the problem?

No, smaller value of 3M9 resistor would cause opposite effect, deeper sweep (as it is part of Voltage divider hooked to the LFO output, where Z1 is made by 3M9 and Z2 is made by parallel combination of 1M resistor, 50n capacitor and all FET gates).

If you will find LFO and this divider working properly, check yet values of all 22k resistors which are in parallel with FET sources/drains - smaller values would cause shallower phase sweep as well.

Btw. if you have chance, make hires photos of your PCB (both sides, more angles..), maybe we will find something odd this way.

Thanks for your help by the way, i really appreciate you taking the time.

You're welcome I've spent lot of time tuning my P90 recently, so I'm temporarily loaded with P90 wisdom

T.