Can anyone help me with a Stereo Tremolo Debug?

[MikeH]

This one's been sitting dead on my bench for about 2 months.

Here's the project file at GGG:
http://www.generalguitargadgets.com/content/view/143/26/

And I used the bipolar power supply from tone pad:
http://www.tonepad.com/getFileInfo.asp?id=118

1.What does it do, not do, and sound like? I get weakened signal through on both channels, but there is no tremolo effect.  The rate LED does not flash, and when the phase switch is in one position it lights up, in another it is off
2.Name of the circuit = Dean's Stereo Tremolo
3.Source of the circuit (URL of schematic or project) = see above
4.Any modifications to the circuit? Y or N.  Yes- I removed the input jack switching from the power supply- which basically meant removing and jumpering the transistor, as well as jumpering the 'ring' pad to ground.
5.Any parts substitutions? If yes, list them.  Just different value voume pots
6.Positive ground to negative ground conversion? Y or N.  No
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 8.95 (I'm not using a battery but this power supply it tested and I know 100% that it is good)

Voltages from the bipolar power supply:
Positive = 8.94
Ground = 0.00
Negative = -8.66

Voltages:

IC1 and IC2 (both TL072) have identical voltages:
P1 = 0.01
P2 = 0.01
P3 = 0.01
P4 = -8.66
P5 = 0.01
P6 = 0.01
P7 = 0.01
P8 = 8.94

IC3 - 4049 (I'm not sure it this should be buffered or not; I'm using an unbuffered IC)
P1 = 6.80
P2 = 6.27
P3 = 0.01
P4 = 0.01
P5 = 6.80
P6 = 0.01
P7 = 6.27
P8 = 0.01 (Pins 8 and 9 started high, ~2v, and fell quickly)
P9 = 0.03
P10 = 0.01
P11 = 0.01
P12 = 5.36
P13 = 0.00
P14 = 5.35
P15 = 0.01
P16 = 0.06

MAX1044:
P1 = 8.94
P2 = 4.43
P3 = 0.01
P4 = -4.36
P5 = -8.66
P6 = 4.38
P7 = 6.61
P8 = 8.94
Thanks in advance for any help anyone can offer!  Please, any information would be helpful.

[Processaurus]

  The rate LED does not flash, and when the phase switch is in one position it lights up, in another it is off[/b]

That is suspicious.  The phase switch shouldn't interact with the rate LED's behavior.

IC3 - 4049 (I'm not sure it this should be buffered or not; I'm using an unbuffered IC)
P1 = 6.80
P2 = 6.27
P3 = 0.01
P4 = 0.01
P5 = 6.80
P6 = 0.01
P7 = 6.27
P8 = 0.01 (Pins 8 and 9 started high, ~2v, and fell quickly)
P9 = 0.03
P10 = 0.01
P11 = 0.01
P12 = 5.36
P13 = 0.00
P14 = 5.35
P15 = 0.01
P16 = 0.06

Pin 8 should be solid at 0v (GND).  Verify it is connected?

[Processaurus]

Mod idea to Deans Design, if you need to get the vactrol LED's brighter:  CMOS gates can sink more current then they can source, so reverse the LED leads on the vactrol and hook the anode to V+, and the cathode to the 2.2K resistors back to the inverters.

[MikeH]

quote]IC3 - 4049 (I'm not sure it this should be buffered or not; I'm using an unbuffered IC)
P1 = 6.80
P2 = 6.27
P3 = 0.01
P4 = 0.01
P5 = 6.80
P6 = 0.01
P7 = 6.27
P8 = 0.01 (Pins 8 and 9 started high, ~2v, and fell quickly)
P9 = 0.03
P10 = 0.01
P11 = 0.01
P12 = 5.36
P13 = 0.00
P14 = 5.35
P15 = 0.01
P16 = 0.06

Pin 8 should be solid at 0v (GND).  Verify it is connected?
[/quote]

I checked it- it is indeed connected to ground, and it is reading zero volts.  I was probably touching an adjacent pin when I was taking the reading.

Regarding the 4049; can anyone verify that a buffered 4049 is ok here?

[MikeH]

Ok, so- i guess I'll try with a UBE.  Any advice from anyone else?

[R.G.]

Yes, you must use an unbuffered 4049. The buffered ones will not work properly in linear mode, which this circuit depends on.

Most of the problem is that your LFO is not oscillating. The need for an unbuffered chip may fix that. It certainly won't work until you get that fixed.

Let us know what happens then.  By the way, "triangle" and "square" are swapped on the switch notations.

[MikeH]

I dug into my stash and found a 4049UBE and plugged it in- LFO still not oscillating.

I pulled a different power supply off my board (just to be sure) and took some new measurements:

TL072s are basically the same

4049UBE:
P1- 7.26
P2- 6.26
P3- 0.00
P4- 0.00
P5- 7.26
P6- 0.00
P7- 6.75
P8- 0.00
P9- 0.00
P10- 7.26
P11- 0.00
P12- 7.26
P13- This one is varies from about 0.18 to 0.35V
P14- 7.27
P15- 0.00
P16- This one is really all over- 0-3V
P16- th

[MikeH]

Is there anyone out there who has built this that could provide voltages for comparison?  Not a lot of info coming up in searches.

Also, I'm 99% sure the orientation of my opto-resistors is correct, but if not that wouldn't cause the LFO not to work would it?  And is there any difference between CLM600s vs CLM6000s?  I'm using 6000s.

[Nasse]

I believe your oscillator isnt oscillating as said before, I would focus on around C6, pot5 and U3D, E, F first. Something wrong there, steady voltages where they should go up and down. Only pins that varies are labeled N.C in the datsheet (not connected)

You could test the opamp and ldr circuits by giving manually the leds some voltage trough safe current limiting resistor

[MikeH]

Thanks- I checked voltages YET again.  This time no movement on those pins, so... maybe the ground connection was coming loose or, my meter was going rouge, or god knows what.

I did notice that I'm getting different voltages depending on how the tri/sq switch is set.  When it's set so that the pole is connected to pin 15 the LED is off, set the other way the LED is on.  Also I get different voltages depending on which way it's set.  Sometimes it's a difference of 1V or so, sometimes a pin will be at 0v on one setting and several volts in the other.  Also, every now and then if I cross 2 pins while metering the LED will turn on or off.  I don't understand much about LFOs using inverters like this so I don't know if that's normal.

Uff. I'm lost.  Perhaps a bit of explanation as to what drives the LFO in this circuit will be enlightening.

Although pin 15 has been at 0V all along, that's not right is it?

[Nasse]

I would take ic 4049 off socket and take some ohm measurements between pins and tracks, so they make sense and are as should per schematic, including speed pot and tri/sq and phase switch too. Should show 470 k between 10 and 11, 1 M between 11 and 15, between 9 and 15 the cap charges and some funny readings perhaps etc etc. But should be easy check if some track is in connection at earth or supply or where it should not

But if the led blinks when toggling switch the audio should "trem" in sync with that

[MikeH]

Just wanted to wrap this up; I check resistances between the pins as Nasse suggested and I found the problem.  Where I should have had 1M of resistance between pins 11 and 15 I had almost no resistance.  And then I noticed that instead of a 1M resistor (brn-blk-grn) I had a 150ohm (brn-grn-blk).  Which was really annoying because it's the SECOND time I've been burned by the same thing.  A while back I bought a bunch of 1Ms and I think a handful of these 150R were mixed in by mistake. Anyway, it's running now.

Although, It doesn't seem to get above unity gain (or what my ear perceives as unity), which I realize is the case with many trems, but I like to be able to get dramatic with my tremolo.