Phase 90 problems

[patrick398]

I realise this has been discussed to death on this forum but didn't find any help on other threads so reluctantly am starting a new one. I've got this phase 90 on breadboard:
http://www.6v6power.ru/inf/Phaser/MXR%20Phase%2090.jpg

I've pulled it apart and put it back together and have finally got signal all the way through it but no phasing. The LFO section isn't oscillating and i'm not sure why. However as a test i tried hooking up the pyscho lfo i've also got on the breadboard and whilst this does vary the voltages on the gates of Q1-Q4  i still don't get any phase shifting.

Some of the voltages look a tad off to me but again i'm not sure why.
I'm using TL072 for all ICs, 2N5952 for Q1-Q4 and 2N4125 for Q5.

Voltages without psycho lfo:

IC1:
1 - 4.96
2 - 4.96
3 - 3.37
4 - 0.00
5 - 4.96
6 - 4.96
7 - 4.17
8 - 9.67

IC2:
1 - 6.2
2 - 5.22
3 - 5.12
4 - 0.00
5 - 1.14
6 - 5.90
7 - 1.39
8 - 9.67

IC3:
1 - 6.55
2 - 6.31
3 - 4.96
4 - 0.00
5 - 5.37
6 - 1.31
7 - 9.14
8 - 9.70

Q1:
G - 3.33
S - 4.95
D - 4.95

Q2:
G - 3.33
S - 4.95
D - 4.95

Q3:
G - 3.33
S - 4.95
D - 4.95

Q4:
G - 3.33
S - 4.95
D - 4.95

Q5:
E - 4.95
B - 4.38
C - 1.59

I realise it's obviously not going to phase if there's no movement from the lfo, i was just wondering if anything else looks amiss? The 9.14 at pin 7 of IC3 definitely seems suspect. Can't work out why there's no phasing even using a different bias for the gate (psycho lfo)

[patrick398]

Also should mention that i'm using 7805 to provide Vref, rathre than the 5.1v zener

[Kipper4]

Also should mention that i'm using 7805 to provide Vref, rathre than the 5.1v zener

Whats The regulator voltages?

I swear Im blind to those upside down transistor diagrams (flat face away) on Datasheets.

[thermionix]

Comparing to this GGG schematic:



Yours is missing C10 and R20.  I think it should work without R20, but I don't know about C10.

[patrick398]

Also should mention that i'm using 7805 to provide Vref, rathre than the 5.1v zener

Whats The regulator voltages?

I swear Im blind to those upside down transistor diagrams (flat face away) on Datasheets.

9.72v on the input, 0v on the middle, and 4.96v on the output.

Comparing to this GGG schematic:



Yours is missing C10 and R20.  I think it should work without R20, but I don't know about C10.

Isn't C10 just a cap between Vref and Vbias? If so it does have one, between the 1M off the trimmer and the Vref. I've definitely got it on my breadboard anyway.

[thermionix]

Isn't C10 just a cap between Vref and Vbias? If so it does have one, between the 1M off the trimmer and the Vref.

Yes, sorry, you are right.  I should spend more time looking before posting!

[Kipper4]

Right. A common mistake I make when doing lfos is to confuse my - + inputs.
Or forget to put the positive feedback loop in.

Yours looks like it might be jammed at the +rail pin 7.

Try disconnecting the lfo from the rest of the circuit. Stick an led in series and a clr on the lfo out put. Does it flash.
Look at RGs page on lfo outputs.

Your transistors?

Did you try wiggling the bias pot ?

I go google voltages.

[patrick398]

Annoyingly have got to move flat this week so might not get a chance to fiddle with it again before then. Hopefully taking it off the board and putting it back together in my new abode will yield some phasey results

[Kipper4]

Rather you than me. Have fun.