Phase 90 problem!

[wui223]

I built a Phase 90 using Tonepad's schematic. But i doesnt phase, keep on hissing and producing noise. WHY? I think i use matched FET ,i test the FET with FET tester suggested at GEOFX, it show 3.2V and i am using a analog multimeter. somebody could help me?

[radio]

hi

which FET as there are four you need 4times same value

as an example in German forum 2 quartett were obtained

of 20    bf245b  one around  2.4  one around  2.8Volt

both worked. Might ne 3.2 is a bit high

Greetings JMErnzer

[Hal]

read taht sticky - what do do when things go poop or something

voltage readings might help.

[wui223]

Ｉtest the FET , diodes, and IC. i list the voltage below. all parts follow schematic from tonepad. FET used is 2N5485.

IC 1
pin: 1-4.1, 2-4.1, 3-1.2, 4-0, 5-2.6, 6-2, 7-4.2, 8-8.2
IC 2
pin: 1-4.1, 2-4.2, 3-4.2, 4-0, 5-4.1, 6-4.3, 7-4.2, 8-8.3
IC 3
pin: 1-4.1, 2-4.2, 3-4.2, 4-0, 5-4.1, 6-4.3, 7-4.2, 8-8.3

FET 1: Drain- 4.1 Source-4.1 Gate-0.8  
FET 2: Drain- 4.1 Source-4.1 Gate-0.8  
FET 3: Drain- 4.1 Source-4.1 Gate-0.8  

PNP 4125: C-0.8 B-4.1 E-4.1

zener: 4.1
1n418: 8.2

thats all, hope someone can tell me why

[LivingDeadPunk]

Are the FET  placed on the board as seen on tonepad layout, i.e flat side on the left?

If so you have to reverse them, there is a mistake in the layout as spotted in one of the build reports.

I had the same problem and reversing the FET (not the 4125) solved it.

Hope it helps

[wui223]

No, i refer the datasheet and i got the correct pin out for that. So it is not the problem, anyway thanks for ur help

[RickL]

Try swapping them anyway. I just finished building this too and mine didn't work either. The first thing I checked was the orientation of the FETs. The datasheet matched the layout orientation so I didn't bother swapping them around and looked elsewhere for the problem. When I saw this thread I figured I would take the two minutes it would take to swap the orientation and that solved the problem.

On the same topic, after fiddling with the 22k feedback resistor and not being very happy with the results I tried Mark Hammer's suggestion to return the feedback loop to the input of the second opamp instead of the first and was very happy with the results. I ended up with a spdt centre-off switch giving me the choices of: no feedback, 22k feedback to the first opamp and 20k trimpot feedback to the second opamp(set just at the edge of whistling). The trimpot could be replaced with a panel mount pot in series with a fixed resistor to give a very usable 'resonance' control.