Phase 45 (evolution) debug help!

[El Heisenberg]

Hey, i built the phase 45 with two extra phase stages like frequencycentral had posted. I pretty much used his layout except without the mallet mods and with the output resistors and 10k resistor instead of the pot. Its basically phase 45 with two more stages.

But it doesnt work like it did on my breadboard. Its a little distorted kinda and the phase sweep seems messed up. When i turn the trim pot all the way counter clock-wise, the sound sorta dies. Ive had this perfed up for a week and a half now (its not boxed up) and ive been trying to find the problem. I checked the build against the schem over and over again. I took voltage readings and took an audio probe to it, but cant find the problem. I searched this forum for voltage readings but can only find wacky ones. No working units. This is my last resort. I hope someone can see somethibg in these readings:

bat: 9.05
vref: 3.46

IC1
1. 3.36
2. 3.38
3. 2.30
4. 0
5. 3.45
6. 3.46
7. 3.56
8. 9.05

IC2
1. 3.35
2. 3.45
3. 3.44
4. 0
5. 3.45
6. 3.46
7. 3.55
8. 9.05

IC3
1. 3.48
2. 3.48
3. 3.48
4. 0
5. 3.20-5.40
6. 3.77-5.80
7. 1.40-8.20
8. 9.05

Q1
G. 1.20
S. 3.46
D. 3.44

Q2
G. 1.24
S. 3.46
D. 3.47

Q3
G. 1.19
S. 3.46
D. 3.46

Q4
G 1.20
S 3.46
D 3.44

i can take measurements elsewhere if its needed. I used 2N5457s and TL072s. 4.7 zener.

Its was a lil difficilt to take measurements on the IC thats part of (i think) the LFO wuteer that stands for.

Please please please help! 

[frequencycentral]

I would initially guess that you may have a 10K resistor missing in that long chain of 10K resistors. Maybe where the extra stages are added. A missing resistor would cause some distortion.

As for the bias - is your biasing arrangement with the trimpot now identical to the original MXR schematic?

MXR Phase 45: http://www.freeinfosociety.com/electronics/schemview.php?id=566

If the problem persists I'll open mine up and take some readings to compare to yours. But check around IC3 pins 1, 2 and 3 - they seem a little higher than the rest - is there a missing 10K there?

[El Heisenberg]

Just went and checked. All the 10ks are in there.I had to use schematic with your layout because mine doesnt have the univibe mods. I also tried remelting the solder around there in case the joints were bad. I mustve done that to every single solder point at this point.

The trimpot arrangement is just like on the schematic.

[frequencycentral]

Did you build the two extra stages on the daughter board as I did? That board was a bit of a kludge to fit everything in a small space, would be worth checking against the schematic for the two extra stages. Particularly check the wiring under the chip, R2, R3 and C4. Also check how you've inserted thetwo extra stages into the main circuit - everything in the right place?





Here's JC Maillet's original schematic, the red letters, A,B, C and D correspond to where I hacked in the two extra stages:





EDIT: Link to original thread so that others know what's being discussed: http://www.diystompboxes.com/smfforum/index.php?topic=76657.0

[El Heisenberg]

Sorry, i shoulda posted links to all that stuff.

Yea, i was checking it just now. I did build the daughter board. Not exactly like the layout becasue i didnt want to mount two resistors and a cap under the ic. I did end up puttind the 10k from pin 1 to 6 under the IC. The daughter board is IC2 and Q3 and Q4. I also ran outta room on the main board since mine was shorter and i put thr .01 cap on IC3 on the bottom.

I was just playing it and when the trimpot is turned all counter clockwise its distorted, instead of quiet like i posted. When it was breadboard, and i turned the pot all the way ccw it would kina dim the sound.

[El Heisenberg]

Well i feel stupid...

It actually was an error in how i had the daughter board hooked up. *whew!* i had to cut two wires and solder each together to the other wire. I had the 10k resistor going to pin 3 an the .047 cap to pin 2. Figures as soon as i go and post voltages here after a week and a half of pulling my hair out i find it actually IS some stupid mistake i made.

Thanks for helpin. I guess at least now there are working phase 45 voltages in the forum now.

[frequencycentral]

.....some stupid mistake.....

You're not the first (me included) and you won't be the last - don't beat yourself up, you built it and debugged it - that's cool. Well done. There's one more thing that I keep meaning to try with mine, that's a Phase 90 style feedback resistor (22K) between the -ve input of the second opamp and the output of the fourth opamp. Maybe you should try it and report back - maybe even try a pot there.

[El Heisenberg]

The fourth opamp? Well ok. Thatd make it the middle one. The one on the daughter board. Whatsit sposed to do? I was plannin on boxin it up today but i think ill go down to radioshack and grt a 5.1 zener to replace the 4.7. A higher vref would make the phase sweep better would it not?

[El Heisenberg]

Or do you mean the opamp that the output is from??

[frequencycentral]

Have a look at the P90 schematic. You see the 22K resistor in red? That's the feedback, or resonance or regen resistor. I guess it should sound 'chewier'.

P90: http://www.tonepad.com/getFile.asp?id=42

[El Heisenberg]

blah! I coulda just made the phase 90!

[El Heisenberg]

Lookin at the schematic, wouldnt i need to connect to the neg input of the 3rd opamp?

[frequencycentral]

Technically, the FET arrangement of the P45 is superior to that of the P90. So don't feel bad. A four stage P45 beats a P90 - and is more unique!  

Lookin at the schematic, wouldnt i need to connect to the neg input of the 3rd opamp?

Yeah, I should have said 3rd to 5th.