Help with Pickdropper Phase 90!

[kinski]

Okay, I decided to pick this back up from the "Box of Fail" and see if I can get it up and running. Basically, its kind of phasing a bit, but its very weak, not smooth at all, and its very distorted, and very noisy no matter where i set the trim pot.

I'd love if anyone could help me out and get this thing working. I've replaced all the ICs a few times over and there is no improvement. Also quadruple checked all resistor and cap values, and reflowed all solder many times over. 

Voltages (trimpot somewhere around middle):

TL061:

1 0v
2 4.5v - 5.5v
3 3.5v - 6.5v
4 0v
5 0v
6 0.5v - 8.5v
7 9.16v
8 0v



TL071:

1 0.15v
2 5.04v
3 3.37v
4 0v
5 0.15v
6 5.04v
7 9.16v
8 0v



TL074:

1 5.04v
2 5.04v
3 4.96 - 5.03v
4 9.16
5 4.96 - 5.03v
6 5.04v
7 5.04v
8 5.04v
9 5.04v
10 4.96 - 5.03v
11 0v
12 4.96 - 5.03v
13 5.04v
14 5.04v



Q1:

C 3.2v
B 4.45v
E 5.04v



Q2-Q5:

D 4.96v - 5.03
G 1.73v - 1.88v
S 5.04

[kinski]

Oh, and here is Pickdropper's link to all of the circuit info:

https://www.dropbox.com/sh/h9ubrun6w0qzeu5/AABIRGeuj16hDIV7dRuwNDpJa/Phase%2090%20v4.7%20(SMT%20FETs)%20Release%20Documents?dl=0#/

[brejna]

Do you have that problem in script mode also or? If you have low/distorted volume problem q1 could be an issue, I've found that as a problem in mine first phase90 build.

[pickdropper]

Phase 90s can be a bit tricky at times.

Brejna's question is good.  If the problem is in block mode, you can try increasing the feedback resistor a little bit and see if that helps.

Sometimes, if it is phasing but there is distortion it helps to change the zener to a lower value.  Often a 4.7V Zener will do the trick.

Alternatively, you can try replacing the zener and setting VB by using a resistor in it's place (which basically sets up a voltage divider with R29).  I would socket it and start with a 10k and go from there.

[kinski]

Thanks guys!

The sounds is bad in both modes, but the noise sounds a bit different in each mode.
I already tried the 4.7v zener. No help.
I'll try replacing Q1. Would a 2n3906 work okay as an alternative?
If that does not work, I'll try the voltage divider.

Do my voltages look okay? Anything look bad?

[brejna]

You can use 2n3906 for q1 and I'll check voltages on mine build..

[copachino]

Thanks guys!

The sounds is bad in both modes, but the noise sounds a bit different in each mode.
I already tried the 4.7v zener. No help.
I'll try replacing Q1. Would a 2n3906 work okay as an alternative?
If that does not work, I'll try the voltage divider.

Do my voltages look okay? Anything look bad?

Its a bit silly to ask but did you match The transistors? What its the matching tolerance

[kinski]

Yup, pickdropper sent me the matched transistors with his PCB.

[brejna]

I've measure voltages, and here are only different ones. Mine are bolded/italic and yours normal. Other voltages were very close or same.
TL071:
3 4,78v  3 3.37v

TL074:
6 5.28v   6 5.04v

Q2-Q5:

D 5.0v   
G 3,8v - 4,2v
S 5.0

D 4.96v - 5.03
G 1.73v - 1.88v
S 5.04

I think you should definitely check R2, R29 is ok I think since is showing 5V. Hope this will help you

[kinski]

Thanks SO MUCH for this! I have not had ANY time to work on the circuit for the past few days. Hoping I'll get some time this weekend. If not, I'll certainly get to it on Monday. I'll report back!

I'll try replacing R2. If that does not work, I'll replace Q1.

[brejna]

Thanks SO MUCH for this! I have not had ANY time to work on the circuit for the past few days. Hoping I'll get some time this weekend. If not, I'll certainly get to it on Monday. I'll report back!

I'll try replacing R2. If that does not work, I'll replace Q1.

Hope it will help you..

[kinski]

Well, sadly no improvements. Messed with the zener, replaced Q1, and replaced R2. Sounds the same. 

[brejna]

Sorry to hear that.. I can't think anything else what could cause the problem..