My Phase 45 problems..

[Michael Allen]

Alrighty, threw this together with some 2N5458, and a 5.1v zener. As is, I'm getting distorted noise with no phasing.....

The LFO is working and I can hear the ticking in the background, changing with the speed pot.

My FETs are matched within .002v with Rob Strand's FET matcher. Pretty sure I've got the pinout right and in the right holes on the pcb. But if I reverse them I get the same sound, so who knows......

Any ideas where to look? IC's have power....I can follow the signal all the way through the circuit with an audio probe...

Thanks,
Michael

[smoguzbenjamin]

Just look where it distorts with your probe. then look around that part for any errors you may have made, or maybe you need to replace something...

[RDV]

Fets socketed?
Which ICs?
Vr is correct?
Diode polarity?
Which schem?

Regards

RDV

[Michael Allen]

Could someone give some IC voltages? So I can compare.....

IC's are TL072s....

Thanks, Michael

[Fret Wire]

Michael, doesn't that use a 4.7 Zener? I don't know if that would matter. Nothing happening when you adjust the trimpot? If you remember RDV's build, discovered the tranny pinout was backward.

[Michael Allen]

Yeah FP's says to use a 4.1V zener, but another says to use a 5.1v. I had a 5.1v so i figured it would be ok.

I can't seem to get a steady voltage to any of the pins except the power pins. Is this normal? On my Small Stone and Phaseur Fluer, I can read steady voltages, but not on this one.....

The voltage that goes to the opamps, the rail that the zener is connected to measeures ~1.5v. Is this about right? I thought it should be about half the voltage of the battery?

I'm pretty sure of the pinouts.....As it is now though, I get the same sounds no matter which way the FET is orientated.....

Also, the trimpot I made a chassis mount pot, and near as I can tell it does absolutley nothing...

So it's still just distorted sounds so far...

Thanks Michael

[Fret Wire]

Also, the trimpot I made a chassis mount pot, and near as I can tell it does absolutley nothing...

That's definately not right. The trimpot adjusts the bias of the FET's. Normally, it has only a small range where it phases (inside that is the sweet spot), and the rest of the range obliterates the phasing. Maybe your particular FET's need a lower value zener. Sounds like a biasing problem.

[Michael Allen]

Alright I'm making progress. Sorta....

I was tracing this through with the audio probe and took out the second IC. I get good signal off of pin 1 so I plug back in the second IC. HOLY COW! Wild siren screeching! The speed pot obviously affects the speed, and the bias is now working. It affects the pitch of this screech. So now i shut off the battery and then plug it back in. And it goes back to the same distorted signal, with no phase.....

So by plugging the battery on and off, and taking the second ic out and in, I occasionally get this wild siren noise and the Vr will be ~4v.

This is the only noise that i get, the signal passes through but without any phase. Only the siren, which i can hear even on the power rail.

I'm pretty certain now that the FETs are orientated right. With one FET in I get a steady screech, and with both FETs in it turns into an oscillating siren.

Man, I'm baffeled..... But the bias is working....

Thanks all,
Michael

[brett]

The voltage that goes to the opamps, the rail that the zener is connected to measeures ~1.5v. Is this about right?

The rail that the Zener (-) is connected to should sit virtually at the Zener voltage (5.1V) since it has a much smaller bias resister (10k) than anything else hanging off that rail.  Is the diode connected the right way around??

good luck

[Michael Allen]

Yeah, the Zener is in the right way....

Still have no idea what to do...

Thanks again,
Michael

[RDV]

Yeah, the Zener is in the right way....
Still have no idea what to do...

What PCB is this? Did you do your own layout, or is it Tonepad's. You have a layout, or wiring problem or both.

Regards

RDV

[Fret Wire]

I'm confused, earlier, you mentioned that you chassis mounted the trimpot. Later, when I asked about it not having an effect when you adjusted it, you mentioned the speedpot. They are not the same. Without the bias properly set by the trimpot, the speed control is useless. If it doesnt turn out to be a connection or solder trace problem, it sounds like a bias problem.

[Michael Allen]

Nope nope, the bias has an affect the whole rotation.  The siren phasing continues no matter where the bias is at. The only thing the bias does is to change the pitch from really high, to a deep growl. I switched out the TL072's for some 4558's and the bias had a more pronounced control. As it was turned it sounded like the sound was being squeezed down. So I'm pretty sure the pot is working correctly.

The LFO is working and changes the speed of the siren. The speed and bias pots work all the time, regardless of the position of the other.

Getting closer here.....

[Michael Allen]

anyone?

[RDV]

You never said which layout, or schematic. There's a good chance if you did the layout yourself that you made a mistake. The Tonepad layout has the op-amps little cutout facing each other.

Regards

RDV

[Michael Allen]

This is FP's layout, stock with no mods....

[Michael Allen]

This is FP's layout, stock with no mods....

Can anyone measure some voltages for me?

[RDV]

I just built that one. I'll do it for you. I'll try to get to it within the next couple of hours.

Regards

RDV

[RDV]

Okay, here goes:

IC1:
1. 3.52v
2. 3.52v
3. 3.52v
4. 0.1mv(ground)
5. 3.37v
6. 3.52v
7. 3.52v
8. 9.73v

IC2:
1. 3.53v
2. 4.6 to 5.35v(oscillating)
3. 4.32 to 5.41v(oscillating)
4. 0.1mv(ground)
5. 3.52v
6. 3.53v
7. 3.53v
8. 9.73v

Q1. D 3.52v
     S 3.52v
     G 3.52v

Q2 D 1.35v
    S 3.52v
    G 3.52v

Zener Cathode(striped) end: 3.52v
         Anode end: 0v

Hope this helps

RDV

[Michael Allen]

Ok. I'm pretty sure you guys are right about the bias. My voltages are similar to yours but about 2v lower. My bias voltage is messed up. The Zener I used was a quick fix from Radio Shack. I'll try the other one (pack of 2) but can I replace it with a resistor in order to bring it to the right voltage? If so, what value will do? THanks a lot....

Michael