Causality 4 MKII Help

[canman]

Hi again everyone,

I built up a Causality 4 MKII phaser, and it worked perfectly fine.  Went to box it up, and all of a sudden nothing was working right.  A couple of wires broke, so I replaced the wires, and removed the rate LEDs at the same time.  Went to try it again, and no dice.  So I thought that maybe the LEDs were crucial to making the circuit work.  Replaced the LEDs, still nothing.  But now only one LED lights up...whaaa???

I can't figure out where I went wrong. 

Some weird things I've noticed...every control apparently works, except for the speed knob (basically, the phasing doesn't happen).  I know this because when I turn the speed knob to anything besides wide open, the one rate LED that lights up starts flashing.  The sound kinda phases, but definitely NOT what it's supposed to be.  So when I mess with all the controls, I can hear them working. 

The problem is, I can't figure out based on the schematic where the problem is.  Here's said schematic:



Can anyone please help an idiot figure out what the heck happened?  I don't even know what kind of voltages I should be checking, since suddenly the other rate LED won't light up anymore...

[bluesdevil]

It's good that it at least worked at one point!
If wires broke and had to be replaced, it's possible other wires could be loose too.

[canman]

That's what's driving me crazy!!  I've triple checked all the wires, I can't find anything wrong...I did find a loose cap...thought it might be the culprit, but it just shifted the behavior of the speed control...now it pulses rapidly at the very end of the taper, but the first 98% of the taper does nothing.  The rest of the controls seem to still "function."

Also, I forgot to post the layout I used:



The 47uf cap at the bottom right of the layout is the one I had to fix...but naturally, it didn't help me much!  I'm starting to wonder if the problem is related to the second rate LED not flashing?

[bluesdevil]

 Check for cold solder joints where things connect to the 2nd rate LED and the wiring (and any components) connected to the 2nd rate control.
Something just shook loose when you boxed it..... gotta find all the bad solder joints! If you can't find anymore visually, I would reflow the solder anyway and see what happens.

EDIT:
Make sure that 2nd rate LED's cathode is connected to ground. That long ground jumper wire could be loose causing it not to flash.

[canman]

So, that long jumper was actually loose, but apparently I've been referring to the wrong LED 

The speed LED 2 as listed on the layout is lighting up...it's the speed LED 1 that I'm having trouble with, along with the speed control.  Even before I noticed the loose ground jumper, it was still working.  So when I fixed it, nothing changed.  Naturally...it's just my luck.

So I tested voltages at the speed LED 1 anode and cathode.  The anode is reading 9v, and the cathode is reading 7v.  Clearly, something is up there.  But when I trace the signal back on the board, I'm only seeing two resistors that are connected to the cathode.  (For reference, the LED that is working is reading about 1.7v on the anode and 0v on the cathode)  When I try to find where the ground connection is to the cathode, I'm getting lost...I know I'm an idiot, so this isn't surprising.  But I just can't find the ground point for that stupid LED!!

What voltages would help in discovering where the problem lies for the speed control?  I have to work for most of the day today but I will be able to post voltages when I get home and can dive into debugging again.

Thanks so much for the help!!!

[Govmnt_Lacky]

Are you using a REV LOG pot for the Speed?

Did any of the wires to the Speed pot get "damaged" during the install?

Did you re-connect these wires to the proper spots?

[canman]

Are you using a REV LOG pot for the Speed?

Did any of the wires to the Speed pot get "damaged" during the install?

Did you re-connect these wires to the proper spots?

I am using a 500k rev log for the speed...had a hard time finding 470k!  When the circuit was working, the 500k didn't seem to make a difference though.

A couple of the wires broke at the lugs of two pots, neither of which were the speed pot.  I didn't reuse those though, I replaced them with fresh wire.

As far as I know, the wires that I replaced were connected in the proper spots...I'll go over it again, but I've checked a few times and haven't seen anything that doesn't line up with the layout.

[armdnrdy]

You should post images of your build.
If it was working and then not....a few more sets of eyes might be able to spot the problem.

[canman]

OK here are a few pics...ignore how ugly and sloppy it is, I know it's not the cleanest.  The resistors are all kinda bent because I've been checking to see if one came loose the past day or so.





I know the solder side is no help, but what the heck:

[bluesdevil]

Maybe not the problem, but looks like some solder splats between copper rows..... see if you can run a utility blade or something sharp between the rows to clean out any potential shorts.

[canman]

Are you looking at the top of the board, maybe three rows down?  I noticed the same thing, on a few rows actually.  It's just light reflections, not actually solder.  I wish it was solder though...

I'll post all my voltages in a little bit, should be leaving work soon.  I may just rebuild it again, and hope for the best.  I just don't get where something is wrong!

[bluesdevil]

The one that caught my eye was on right side, between rows 5 and 6 from bottom. If you had this circuit working before, I might be just steering you in the wrong direction, though.
It sucks to have to rebuild..... hopefully somebody with a good pair of eyes can spot something before you give up.

[canman]

Well, I've built one of these before...actually, I built it and boxed it and it was working wonderfully, but then this guy wanted me to put it in a box with a chorus, so I figured I'd just move it over.  Then somehow it went bust on me!

Anyways, here are my voltages:

IC1 (LM13700):
1: 1.17
2: 0
3: 4.5
4: 4.69
5: 5.27
6: 0
7: 5.27
8: 4.72
9: 4.72
10: 5.16
11: 9.43
12: 5.17
13: 4.74
14: 4.58
15: 0
16: 1.16

IC2 (TL074)
1: 4.72
2: 4.74
3: 4.52
4: 9.42
5: 4.62
6: 4.73
7: 4.73
8: 4.72
9: 4.73
10: 2.67
11: .09
12: 4.57
13: 4.72
14: 4.72

IC3 (TL072)
1: 4.79-4.84 (Sporadic)
2: 4.7-4.9 (Sporadic)
3: 4.3-4.33 (Sporadic) (Yes, it only changes .03)
4: 0
5: 4.8
6: 4.8-4.82 (Sporadic)
7: 4.88-4.91 (Sporadic)
8: 9.42

So, it looks like the TL072 is having difficulties.  I'm pretty sure it's not working properly, since from what I've read, it is being used as the LFO.  The voltages certainly aren't swinging like I'd think they should be...any thoughts?

[canman]

Whoa...found the working voltages that Rick Holt posted:

NE5532 (TL072)

1. 1.32v to 8.44v
2. 3.56v to 5.81v
3. 3.45v to 5.77v
4. 0v
5. 3.56v to 5.84v
6. 3.55v to 5.85v
7. 2.89v to 7.02v
8. 9.10v


TL084 (074)

1. 3.89v to 5.34v
2. 3.87v to 5.37v
3. 3.85v to 5.30v
4. 9.10v
5. 3.63v to 5.02v
6. 3.87v to 5.33v
7. 3.87v to 5.33v
8. 3.87v to 5.33v
9. 3.87v to 5.35v
10. 3.85v to 5.31v
11. 0v
12. 3.87v to 5.33v
13. 3.88v to 5.33v
14. 3.87v to 5.33v


LM13700

1. 1.304v to 1.373v
2. 0v
3. 3.87v to 5.33v
4. 3.87v to 5.33v
5. 5.05v to 6.51v
6. 0v
7. 5.03v to 6.53v
8. 3.87v to 5.33v
9. 3.87v to 5.33v
10. 5.03v to 6.53v
11. 9.10v
12. 5.05v to 6.51v
13. 3.87v to 5.33v
14. 3.87v to 5.33v
15. 0v
16. 1.304v to 1.373v

Something is causing all of my IC's to not "phase"...I'm getting mostly static voltages on the TL074 and the LM13700, and they hardly move on the TL072.  Is it possible for the potentiometers to prevent the voltages from swinging?  Or should I be looking for something on the board?

[canman]

Update...rebuilt everything from the ground up.  Still having the SAME EXACT PROBLEM.  Could it be the speed pot somehow got fried?

[Govmnt_Lacky]

Not for nothing but....

I noticed that Rick used a NE5532 for his LFO amp. Did you try using that chip? Or... try using an LM358. Some op amps do not work well in LFO circuits 

[canman]

The TL072 in the rebuild seems to be OK...I have some interesting updates.  But thanks for the tip, I will certainly keep that in mind!!

The C500K pot clearly wasn't doing what it was supposed to, so I figured I'd throw in a B100K in place of it, just to see if the pot was the problem or the circuit was the problem.  I know it isn't the right taper, but I think the 500K pot went bunk on me.  When I turned the 100k pot up, there is very slight phasing, but the last 1/4 of the taper is where all the action happens.  If I'm careful when turning the shaft, I can get all the different speeds of phasing that the normal C500K should get.  So I think somehow the C500K pot just took a dump.  Also, when the 500K pot is attached, absolutely nothing happens until the VERY last segment of the taper, and when the phasing kicks in, the other controls don't do anything.  They all work perfectly fine with the 100k.

Does that sound right to you guys?  Are these symptoms of a bad pot?

[bluebunny]

This does sound exactly like my first P45 build.  Nothing until the very end of the pot travel.  Turned out this was down to a cracked track, so it was open circuit most of the time, until the wiper got past the crack right at the end.

[canman]

That's really interesting...did your pot come with the track cracked?

I don't remember overheating this pot, but I guess somehow the track could have cracked some other way..?

[bluebunny]

Could have been - difficult to tell after the event.  Could have been damaged in transit, or me being heavy-handed installing it.  I don't think it could have been heat damage.  Mechanical abuse, more likely.  When I took it out, the lug and its bit of track actually fell off completely!