Help with phase 45

[Tauron]

Hi all, I'm new to the forum and i am looking for some help in debugging the mxr phase 45 Ive recently built.

- The schematic used is the one from tonepad http://www.tonepad.com/getFile.asp?id=70 and no mods were done. (only 50nF capacitors were replaced by 47nF ones)

- I am using a pair of self-matched JFETS 2n5485 using the method seen in http://www.geofex.com/article_folders/fetmatch/fetmatch.htm, and the two measures were
    Vgs1=1.418v, Vgs2=1.429v (the closer i got). and i have taken into account that the pinout of 5485 is reversed from the one shown in the tonepad layout (for 5952)

- After building the whole board and mounting the ICs and transistors, i switched on the effect and started to adjust the bias trimpot from far left to right, the sound on the left is the clean guitar with no phasing at all nor any other effect. As long as i turn the trimpot clockwise i find a point where i can hear a variation in the sound, i hear the sound of the guitar oscillating and with the speed potentiometer can change the speed of the oscillation. Right after building it i thought that i had found the point and had a phaser yet but by researching some sound clips of other phaser 45 i realized that mine was not sounding the same way. Its hard to define the sound as I'm not a native english speaker but it is something like i can hear the oscillation a phaser do, but without hearing the phase change itself, instead i note a volume or richness change in the sound, going from full volume clean guitar to a more thin, less rich sound. When i continue rotating the bias trimpot clockwise this effect is more and more extreme to the point that there is a nearly muted-full volume change between oscillations.

- I have took voltage readings at IC pins and JFET:

IC1: (the one on the left in tonepad layout)
P1: 3.91v
P2: 3.91v
P3: 3.85v - 3.89v
P4: 0
P5: 2.62v
P6: 3.91v
P7: 3.91v
P8: 8.89v

IC2: (the one on the right)
P1: 4v - 5.70v (changing limits as i turn the speed pot)
P2: 4.32v - 4.92 (changing limits as i turn the speed pot)
P3: 3.88v - 4.50v (changing limits as i turn the speed pot)
P4: 0
P5: 1.05v - 1.06v
P6: 2.65v
P7: 1.43v
P8: 8.88v

Q1 (left)
D: 3.91v
S: 3.89v
G: 0.86v - 0.96v

Q2 (right)
D: 1.05v - 1.06v
S: 1.05v - 1.06v
G: 0.86v - 0.96v

Thanks for helping, i hope someone can point in the right direction because i have checked the circuit million times and i am unable to understand whats going on.

[Tauron]

Any idea?

[Fender3D]

You should get similar readings on FETs pins... 
The trouble is your pedal somewhat works!
You should check your FETs area, if you don't find any visible issues there,it's time for a scope....

[Kearns892]

I was about to suggest double checking the pinouts. JFET pinouts for similar devices will vary by manufacturer, but is seems like he is getting the oscillating part of the phaser to work which suggests his transistors may be oriented correctly. I would check the components in the audio path. Did you socket your ICs?

[Tauron]

First, thank you for replying.

Second: I am going to check the FETS area as suggested to see if there is any soldering issue or anything else althought i have checked the whole circuit lots of times. I have the ICs and FETs in sockets so i am discarding a pinout error (i have the datasheet of the 2n5485 but i have tried the two possible ways of connecting them and i only get the oscillation in one, other way sounds clean guitar always).
Both of you have pointed out the problem can come from FETs zone, can i assume the voltage readings on ICs are corrects? and could you please tell me what FET has the wrong values, or the problem is only that both have different readings? (i dont know so much about the correct voltages in this circuit but it seems to me that Q2 has somewhat odd values taking into account other people readings i have seen in this forum)

Thank you in advance.

[Fender3D]

Gs and Ss should have the same voltages (S=Vbias, G=VLFO) for both FETs.
Ds should be ~Vbias.
IC2b readings are way to low. I don't know if its Q2's fault or IC's...
Swap the 2 ICs and you'll see...

[Tauron]

You should check your FETs area, if you don't find any visible issues there,it's time for a scope....

YOU DID IT MAN THANK YOU VERY MUCH!!

Since Q1 readings seemed somewhat coherent to me and Q2 ones were odd i have checked again all the soldering points around that point, i found a joint that seemed weak so i resoldered it and voila! a perfect phasing sound (to me at least) came from the amplifier, it sounds really cool and i have to thank you the help again. i was totally desperated about this project and you pointed me into the right direction!