Stage Fright - No phase effect

[Domdec314]

I'm having trouble with my Stage Fright. The sound is cleanish. There's no phase effect. The Speed knob doesn't do anything and the Rate LED doesn't turn on. With the switch to the left, the Balls knob make its bassier as it's turned clockwise. With the switch to the right, the tone is weaker and tinny and the Balls knob make it tinnier as it's turned clockwise.

I put an audio probe on it, but I'm really not sure what to look for. I've never done a phaser before. There doesn't seem to be any audio going in and out of the TL062, but I'm not sure if there's suppose to be. The trimmer doesn't seem to do anything until roughly the last 5% (clockwise). At that point, the tone gets honky, as if the phase was paused.

The only substitution I made is a 3.3k resistor instead of a 3k resistor.

Any help would be greatly appreciated. I was hoping to have this for my brother for Christmas, but I procrastinated and left no room for errors. 

[Scruffie]

Post voltages, let's see if you can finish it in time...

[Domdec314]

Here ya go. The voltages were all steady. No fluctuations. I'm using an analog multimeter so these are close approximations:

IC1 (TL074)
1. 4.4v
2. 4.4v
3. 0.8v
4. 9.4v
5. 2.4v
6. 4.4v
7. 4.4v
8. 4.4v
9. 1.4v
10. 1.2v
11. 0v
12. 2v
13. 4.4v
14. 4.4v

IC2 (TL062)
1. 0.8v
2. 0.6v
3. 0.4v
4. 0v
5. 4.4v
6. 0.1v
7. 8.8v
8. 9.4v

IC3 (LM13700)
1. 1.4v
2. 0v
3. 4.4v
4. 4.4v
5. 4v
6. 0v
7. 4v
8. 4.5v
9. 4.4
10. 3.6v
11. 9.4
12. 3.6v
13. 4.4v
14. 4.4v
15. 0v
16. 1.4v

IC4 (LM13700)
1. 1.4v
2. 0v
3. 4.4v
4. 4.4v
5. 4v
6. 0v
7. 4v
8. 4.4v
9. 4.6v
10. 4.9v
11. 9.4v
12. 4.9v
13. 4.4v
14. 4.4v
15. 0v
16. 1.4v

IC5 (LM13700)
1. 1.4v
2. 0v
3. 4.4v
4. 4.4v
5. 3.6v
6. 0v
7. 3.6v
8. 4.6v
9. 4.4v
10. 5.4
11. 9.4v
12. 5.4v
13. 4.4v
14. 4.4v
15. 0v
16. 1.4v

[Scruffie]

You seem to have a lot of voltage issues in different places... I would guess you have a short or cold joint (or a few) but it's a little hard to pin point... can you post photos of the board?

Some of the readings I think may be down to impedance of your meter... but pins 8,9 & 10 of the TL074 look particularly suspect though, but i'd start with the TL062 (LFO) it's locked up and seems to be pulling down voltage so re-flowing the joints around it and the associated components will probably be a good start and checking carefully for any solder hairs and making sure each joint is shiny.

[Domdec314]

Here are two pics of the board. I went over every pad and made sure they were all shiny. Unfortunately, that didn't fix it.

[Domdec314]

Is it possible that the TL062 is bad? Like I said, I don't have a strong understanding of how phaser work so I'm really not sure what to look for. Is the TL062 suppose to be passing audio? My audio probe is coming up silent.

[Govmnt_Lacky]

1) Pull that TL062 and put a socket in there! 

2) Re-try the TL062 (in the socket). If that doesn't work, try another TL062 or even an LM358 (My go-to LFO op amp)

I agree with Scruffie. You definitely have no oscillation coming from the LFO.

Good Luck 

[Domdec314]

I had a socket there, but the input jack wouldn't fit when everything was in the case. I know I shouldn't have assembled it in the box but I was in a hurry and was a bit cocky since the last 12 or so pedals I've built came together without issues. Also, the issue was still there when the TL062 was socketed, so I'm pretty sure I didn't burn it.

[stevie1556]

If it's any consolation, mine isn't phasing either and I'm scratching my head!

Hope ya get it sorted soon!

Sent from my thumbs using Tapatalk!

[Scruffie]

Lift one leg of R47 & R51 and see if the TL062 voltages change.

[Domdec314]

Lift one leg of R47 & R51 and see if the TL062 voltages change.

Here are voltages now:

TL062
1. 0.6v
2. 1.6v
3. 0.2v
4. 0v
5. 4.4v
6. 0.6v
7. 8.6v
8. 9.2v

[Scruffie]

That isolates the LFO, the V.Ref is doing its job as you have half supply (near enough) on pin 5.

Check the values R43 to 46 and C14 to 16, triple check the solder joints, if you have any Op-Amps such as a TL022, LM1458, LM358, RC4558, another TL062 try them out in the socket in place of IC2, you should be seeing a moving voltage on Pin 7. Also check C19 and the rate pot.

[Domdec314]

Update: I got frustrated and started over with a new board. The LFO section is working now, but there's still something weird going on with the switch. With the switch in the left position (5-stage) the tone is full and bassy, but in the right position (6-stage) it's weak and thin sounding. I'm using the same LM13700 and TL074 ICs from the previous build. Is it possible one of them might be the issue?

Here's a quick sound clip I just recorded. The Ball pot is full up and the Speed pot is about in the middle. First you hear the clean signal, then the pedal set for 5-stages, then finally set for 6-stages.
https://soundcloud.com/highmileage/phasertest

[jimilee]

Sounds about right man, everyone has noticed that phenominon. Awesome phaser. Lost mine in a deal for a new bass, now I gotta build another.

[Domdec314]

Interesting. The video linked in the PDF show a much more subtle difference between the two modes. (http://www.youtube.com/watch?v=nZwEXghYrp8). It seems weird to me the adding a phase stage would diminish the tone, but if that's the way its suppose to be, then I call the project complete.