Need help debugging MXR Phase 90

[LEON.01]

Just finished the phase 90 from this layout;


The problem is i get a signal when bypassed and when the effect is on, but the effect just isn't phasing!!! 

All subs used are;
0.05 uf caps changed to 0.47 caps,
15uf cap to 15uf non polar,
250k trmmer to 100k trimmer,
IC's are TL072CN, X2 and a TL072CP.
JFETS used are 2N5457
PNP used 2N3906.
Some caps are ceramic, some are poly but i believe thats not the problem.

Voltages;  Battery=9.15

IC1 TL072CP
1=4.39
2=4.39
3=2.97
4=9.03
5=3.16
6=0.87
7=8.02
8=0.00

IC2 TL072CN
1=1.00
2=8.01
3=4.33
4=9.00
5=4.33
6=4.42
7=6.75
8=0.00

IC3 TL072CN
1=2.15
2=4.41
3=4.32
4=8.98
5=4.49
6=4.32
7=6.82
8=0.00

Q1 2N5457
D=4.29
S=4.39
G=4.39

Q2
D=4.29
S=4.39
G=4.39

Q3
D=4.29
S=4.39
G=4.38

Q4
D=4.47
S=4.38
G=4.38

Q5 2N3906
E=4.38
B=4.38
C=4.38

If thrs anything i've missed, please let me know.

Cheers fellas!

[R.G.]

You have pinout naming problems to start with. Either you are calling the wrong pins pin 1-8 on the ICs or the ICs are in backwards. Pin 4 on dual opamps must be the lowest voltage, pin 8 the highest. Yours is the reverse, although the layout shows them connected correctly.  Also, Q5 has all the pins at the same voltage, which cannot work. Something is hosed about the connections to Q5.

[LEON.01]

Hi R.G.

This is how i've been naming them, as numbered here;


Socketed them the same as the layout.

Could i be taking the voltage's wrong to get these reading's or is there only one way of taking them?

Replaced Q5 with another 2N3906. Different readings but still no effect.

Q5
E=4.34
B=4.69
C=7.48

I know all the JFET's should match, I haven't matched them! But i assume i would get some kind of phasing effect even if they are not, no?

But now you've mentioned that the IC's sound they are completely messed up, i have become worried!!! 

Some more info, don't know wether it will help or not!

When i remove Q1, Q2 or Q3 when the effect is on, nothing happens. When i remove Q4 the volume drops a bit and you can here i little overdrive. When Q5 is removed thr is no sound.
This probably means nothing, but, just in case!

Thanks.

[LEON.01]

Ok!
Checked a few things and had something wrong! 

NEW voltage readings;

IC1
1=4.64
2=4.64
3=3.13
4=0.00
5=4.92
6=1.08
7=8.09
8=8.95

IC2
1=1.63
2=8.08
3=4.53
4=0.00
5=4.53
6=4.64
7=6.87
8=8.93

IC3
1=2.45
2=4.78
3=4.53
4=0.00
5=4.36
6=4.28
7=6.37
8=8.92

Q1,Q2,Q3
D=4.53
S=4.63
G=4.63

Q4
D=4.36
S=4.63
G=4.63

Q5!
E=4.63
B=4.06
C=1.36

[LEON.01]

Made R.G's FET matcher, matched four! still not working! retouched some dodgy looking solder joints, still not working! Fantastic! 

[anchovie]

Did you fit your JFETs using the same orientation as the layout? The layout is for 2N5952s and you may find that your 2N5457s need to be rotated 180 degrees to what the image shows.

www.fairchildsemi.com/ds/2N/2N5952.pdf
www.fairchildsemi.com/ds/2N/2N5459.pdf

You also said that you subbed the 0.05uF caps with 0.47uF - is this correct? 0.047uF would be the "nearby" value.

[R.G.]

IC1
1=4.64
2=4.64
3=3.13
4=0.00

Probably OK.

5=4.92
6=1.08
7=8.09
8=8.95

Pin 7 should be whapping back and forth from about 1V to about 8V, at a speed determined by the speed pot. Does it ever flip? If not, something is hosed up here.

IC2
1=1.63
2=8.08
3=4.53
4=0.00

If the voltages are correct, pin 2 is being pulled up to 8V somehow. Solder? Uncut trace? Wrong placement?

5=4.53
6=4.64
7=6.87
8=8.93

OK-ish, but I'd expect pin 7 to be down at about 4.5V too. Odd, but other things to worry about first.

IC3
1=2.45
2=4.78
3=4.53
4=0.00

Probably OK for the moment. Sort other things out first.

5=4.36
6=4.28
7=6.37
8=8.92

Same comment as last two.

Q1,Q2,Q3
D=4.53
S=4.63
G=4.63

Q4
D=4.36
S=4.63
G=4.63

Very odd. I think you need to check the JFET pinout for the actual devices you used.

Q5!
E=4.63
B=4.06
C=1.36

Probably OK.

Go check the ones I suggested and verify your JFET pinouts and placement. Then come back with a new set of numbers.

[LEON.01]

Ok!
All Transistors have been checked and are in the correct positioning.

New Transistor readings;

Q1,Q2,Q3 & Q4
D=4.52
S=4.62
G=1.13

Q5
E=4.62
B=4.07
C=1.16

The Zener is a 5V1 and is reading 4.62

Checked cuts, jumpers, soldering and placements. Everything is to the layout. Can't get the voltage from IC2 pin 2 down!!!

Pin 7 on IC1 changes only when the pot is turned.

Think i bit off more than i can chew with this one!!!

[ayayay!]

You said you used a 100k trimmer? 

[LEON.01]

You said you used a 100k trimmer? 

Yep, went to MAPSHITE for a 250k trimmer and ended up with a 25k trimmer!!!!!!!! WTF!

100k was the closest i had to hand. got some marked 222, 223 and 224! Don't know if thr the values of them or not though!

Would a change in trim pots cause the problems i'm having though?

Think i'm going to end up ditching this and trying the 45!!!! 

[ayayay!]

Easiest way to tell is to get your meter out and measure those trim pots.  You can get one for $4.00 at Harbor Freight.

I'd think a 250k is necessary, because even on a good working Phase 90 the working range for that pot is very narrow, and the sweet spot is even smaller.  I seem to recall the useable range on mine was between 120k- 150k.  Outside of that, the effect won't work. 

Dunno, I'd think it would still work with a 100k, but you need to try it to be sure. 

[mdh]

224 should be 220k, but yeah, measure it.  The way to read those markings in general is to take the first two digits to be the significant figures, and the third digit gives the number of zeros.  So 224 = 22 0000 = 220,000 = 220k.

But don't worry too much about the trimmer until you get the LFO working (that's what R.G. was getting at when he asked if pin 7 of IC1 was banging back and forth between 1V and 8V).  Make sure the speed is turned down at least halfway or so, so that you'll be able to see the changes in voltage if they're there.  I wish I could give you more advice on exactly how to troubleshoot the LFO, but others here should be able to.

[beatnik]

I'm bumping this again because my last phase 90 is not working correctly.

I have guitar dry signal coming to the output, but i don't have the phasing effect, setting the trimmer or the rate pot doesn't make changes.

I have already checked for component values and solder bridges, but everything seems to be ok. The only substitutions i made are 22uF instead of 15uF polar capacitor, 220K trimmer instead of 250K and a matched set of MPF102 FETS (flipped 180°for matching pins)

Here are my voltages, i hope someone could spot the problem, thanks in advance.

IC1 RC4558

PIN1: 4.73V
PIN2: 4.73V
PIN3: 3.19V
PIN4: 0V
PIN5: 3.30V
PIN6: 4.90V
PIN7: varying
PIN8: 9.24V

IC2 RC4558

PIN1: 4.59V
PIN2: 4.66V
PIN3: 4.56V
PIN4: 0V
PIN5: 4.50V
PIN6: 4.66V
PIN7: 4.72V
PIN8: 9.24V

IC3 RC4558

PIN1: 4.61V
PIN2: 4.64V
PIN3: 4.57V
PIN4: 0V
PIN5: 4.54V
PIN6: 4.64V
PIN7: 4.70V
PIN8: 9.24V

Q1, Q2, Q3, Q4 MPF102

G: 0V
S: 4.66V
D: 4.45V

Q5 2N4125

E: 4.66V
B: 4.05V
C: 2.70V