Phase 90 Debugging - gated distorting

[Crowella]

So I attempted a Phase 90 using the Tonepad layout and I'm getting a very quiet, no phase sound from the guitar unless I strum very hard which results in a gated distortion/fuzz sound.

Using a multimeter...

Voltage Source: 9.18V

D1:
A = 0
K = 9.18V

Z1
A = 0
K = 4.35V

Q1:
D = 4.34V
S = 4.34V
G = 2.6V

Q2:
D = 4.34V
S = 4.35V
G = 2.59V

Q3:
D = 4.35V
G = 4.34V
G = 2.59

Q4:
D = 4.34V
G = 4.34V
G = 2.59

Q5
C = 3.75V
B = 3.74V
E = 4.35V

IC1
1 = 2.3
2 = 2.3
3 = 11.21 ()
4 = 0
5 = 5.38 (still)
6 = 2.5 (bouncing around between 2 and 2.8 )
7 = 8.59 (still)
8 = 9.18

IC2
1 = 6.06 (couldn't get exact here, but it was moving between 5 and 6.
2 = 4.38
3 = 4.37
4 = 0
5 = 4.37
6 = 5.49
7 = 2.96
8 = 9.18

IC3
1 = 3.81
2 = 4.35
3 =4.35
4 = 0
5 = 4.35
6 = 4.35
7 = 4.96
8 = 9.18

15uF
+ = 4.89
- = 0

10uF
+ = 4.34
- = 0

[Mark Hammer]

Whenever I get someting like that, it usually involves an electroytic cap the wrong way around.

[R.G.]

Q5
C = 3.75V
B = 3.74V
E = 4.35V

With the collector and base at the same voltage, no signal can get through. Something is wrong with the collector side of this transistor. Perhaps the collector resistor is open, perhaps there is a short to the base. But something is wrong here.

IC1
1 = 2.3
2 = 2.3
3 = 11.21 ()
4 = 0
5 = 5.38 (still)
6 = 2.5 (bouncing around between 2 and 2.8 )
7 = 8.59 (still)
8 = 9.18

Something is wrong here. Pins 1, 2, 3 should all be close to 4.35V. Pin 3 reading is incorrect.

Also, pins 5, 6, and 7 should be moving. Pin 7 should alternate between about 7V and 2V. Check the components, orientation and soldering on this IC.

IC2
5 = 4.37
6 = 5.49
7 = 2.96

Something wrong here. Check connections and soldering on this part.

IC3
1 = 3.81
2 = 4.35
3 =4.35
4 = 0
5 = 4.35
6 = 4.35
7 = 4.96
8 = 9.18

These are OK. IC2 should look like this.

15uF
+ = 4.89
- = 0

This is where the main LFO waveform happens. This should ramp up and down, not stay steady at 4.89. This matches the earlier note about IC1b not being connected correctly.

10uF
+ = 4.34
- = 0

S'OK.

[Crowella]

Since it's 2am and I'm drunk, won't attempt any look at that until morning, but thank you all for your assistance. I think it may be two or three spots going into IC1 and Q5.

[Crowella]

Thank you so far. I have solved the issues with the IC's (one slightly disconnected joint).

I now have all the gates on the 4 JFETs at 4.3V and can't be adjusted by the trim.

Q5 is also...
C = 4.06
B = 4.24
E = 4.34

[R.G.]

Thank you so far. I have solved the issues with the IC's (one slightly disconnected joint).

I now have all the gates on the 4 JFETs at 4.3V and can't be adjusted by the trim.

Bad/open trimmer, bad/open solder joint on the trimmer, bad/open resistor from trimmer to JFET gates, etc. Use your DMM to read the voltage on the wiper of the trimpot, verify that it goes between ground and 4.3V, and then set it to some middle voltage if it does and follow that through the circuit to the JFET gates. Where it quits being the trimmer voltage, check for problems.

Q5 is also...
C = 4.06
B = 4.24
E = 4.34

That might be OK-ish, might be a problem. Let's solve the JFET gates first.

[Crowella]

The 250k Trimpot works fine and I have it set at 1.8V for now. At the trimpot side of the resistor it is 1.8, then it goes to 4.3V along that rail still. The trimpot does full rotation from ground to 4.3V and all in between.

I have a feeling that the 1M resistor is faulty, so I'll swap it out.


Forgot to mention I have a clean sound, no phasing.

And R.G. Thank you so much for your help. I might have been with the multimeter for 3 hours now but I'm at least learning what to do (and what not to do)   First time making a PCB and it's going better than I expected at least.

[Crowella]

All fixed now. one of the JFET's was broken. I replaced it with a new set and now it's working like a charm.

Thank you so much for your help, it is really appreciated