Need a little help again with a mxr phaser 90

[whomeno]

built form this site. built the one with just a switch.
http://tagboardeffects.blogspot.com/2014/05/mxr-phase-90-with-script-switch.html
when on I can hear the swishing but no audio.
the top ic voltages is way high.
checked for shorts none found.
I messed up a few cuts but fixed them.










Voltages    8.74 in put

top ic
1   8.14
2  8.03
3  8.47
4  0
5  8.47
6  8.11
7  8.15
8  8.74

middle ic
1  7.99
2  4.71
3  8.48
4  0
5  8.48
6  8.10
7  8.12
8  8.74

bottom ic
1  1.47
2  1.47
3  .94
4  0
5  .92
6  1.04
7  1.41
8  8.74

q1
d  8.41
s  8.60
g  1.62

q2
d  8.38
s  8.49
g  1.62

q3
d  8.35
s  8.44
g  .90

q4
d  8.35
d  8.62
g  2.50

q5
c  0
b  4.46
e  .64

[patrick398]

Your voltages are definitely off but if you have wooshing that implies the lfo and fets are behaving correctly...though the voltages are pretty out there. Is it an even, up and down shifting in pitch like you'd expect to hear from a phase sweep?

Here are voltages i took from mine when i was trying to get it going. I had the opposite problem, audio was fine but i couldn't get the lfo firing so perhaps ignore the second half of IC3.

I'd start by finding out where the 8(ish) volts all over IC1 was coming from.
HTH


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

[whomeno]

I am stumped. there is a 10k feeding q1 -4 with 8.77v  they then feed pin 3 of top ic with 8.5v and pin 5 is getting 8.59v. both top and middle ic is the same.
ic's are out. they should be getting 4.5v in pin 3 right?

[antonis]

Check for DC voltage on socket pins without ICs in place..!!!

[whomeno]

that is what i did

[whomeno]

top ic
1  0
2  0
3  8.52
4  0
5  8.52
6  0
7  0
8  8.79

middle ic
1  0
2  0
3  8.45
4  0
5  8.50
6  0
7  0
8  8.79

bottom
1  0
2  0
3  0
4  0
5  0
6  0
7  0
8  8.79

[antonis]

Hmmm...
(cemetary bias..)

Maybe some misplaced cuts..??

[whomeno]

I have rechecked all cuts, shorts and componet placing. everything looks good

[patrick398]

Why the different voltage readings? Is one with IC in and one with IC out?

[whomeno]

yes last set is without

[antonis]

As far as I can trace, left part of lower IC should be Input buffer & right part should be LFO..
That said, it should have bias on both its non-inverting inputs..!!
(pin3 via 470K and pin5 via 150k respectively..)

Check voltage on Zener (D1) anode and, if it's OK (about 5V1), trace left for discontinuity..(red dots..)
If not, trace upwards.. (green dots..)
If not again, trace for 9V (blue dots..)

[whomeno]

Thank you, working great now. bad connection at the top of link beside 10k.
how do you know where all the 5 volt was? I still trying to learn schmatics.
I can read truck schmatics with no problem.
Thanks again

[antonis]

Boards aren't actually schematics (although they ought to follow them..)

If you trace from 9V DC input, you'll meet a 10k resistor going to FET Source but also to the jumper 4 holes to the right..
That jumper comes down to BJT Emitter but also to D1 anode 2 holes left..
D1 cathode is set to GND via the longest jumper 7 holes on the left so its anode should exhibit its nominal zener voltage (5V1)..
Everything connected there (the whole 18th row) should also "carry" that voltage..
Non-inverting inputs should be considered of VERY high resistance so there isn't any current flowing into them..
No current through a resistor means no voltage drop on it, hence same voltage on both legs of each bias resistor (150k & 470k)

But, a schematic (electronic diagram) should be more helpful..
(in the mean of implementaion voltage measurements for board troubleshooting..)

[whomeno]

thank you for the information. it will help me out alot