Phase 45, again

[Michael Allen]

I've got it working here for the most part. Turning the trim is like a manual sweep through the phase range, but my LFO is not working. My dmm broke so what should I check out first to get the LFO pumping. I'm blind without the DMM here..

Thanks!

[Paul Marossy]

First off, how did you build it? The tonepad layout?

[Michael Allen]

yup, Tonepad.

[Paul Marossy]

I'm no expert when it comes to phasers, but my initial thought is that you may have a mismatched pair of FETs. Also, are you sure that your opamps are functioning properly?

[smoguzbenjamin]

You should be able to get a cheap, simple DMM for 5 bucks, that will at least give you some idea of what's going on. I'd say get a cheapo meter so you know what's going on.

[Michael Allen]

Nope, FETS are matched. Two best out of 25, 2N5458. The Opamps work fine, the prob is with the LFO. I'm not getting any modulation. I'll obtain another multimeter somehow in the next few days, so untill then...

[Paul Marossy]

Hmm... that is curious. I am interested to hear what you find out. I just built one using the same layout, didn't match the FETs, and it works just fine...

[RDV]

Electros correctly polarized? Both jumpers installed?

RDV

[Paul Marossy]

On a few things that I have built, I had a tiny solder bridge shorting out something next to it...
Just another idea of things to look for.  

[smoguzbenjamin]

Long live the 3rd hand with magnifying glass

[vdm]

make sure of the fet orientation... that's all i have to say

trent

p.s. you could also try putting a 2.4k then led to ground from pin1 of IC2a - this will blink in time with the oscillator and let you know if it is oscillating at all

[Michael Allen]

Well it's the LFO i'm positive. Using an analog multimeter set on DCV with the com terminal to circuit ground, the LED i attached to pin 1 of IC2 will light up a little when I touch the Red probe to pin 1 and 3 and will light a lot when i touch pin 2. I think there is not power getting through. I replaced the 150ks with 100k's (the 150's were a combo of 100k and 47k) just to test, and no result. Occasionally when the power is disconnected and then reconnected the LED will light but then go away. There is no oscillation coming from the LFO. The rest of the circuit is fine. I can't see any bridges or bad connections. I've melted most of them over again.

Thanks!

[Paul Marossy]

Hmm... must be possessed by some evil spirit.  :wink:
Are you sure that your opamp is good? That's all I can think of at the moment.

[Michael Allen]

Yeah brand new. Tried a few

[Paul Marossy]

Strange. I built the same circuit a few weeks ago using the same PCB layout and it works great. I am not sure why yours isn't doing the phase dance thang. It ought to be working...

Are you absolutely sure that all your resistors and caps are all the right values, etc.? Have you tried different FETs? I used J201s in mine, and they work.

[Michael Allen]

This really is a bugger. I fear I might have a part mix up somewhere because on my first try the LFO worked but the thing wouldn't sweep/phase. Now the LFO won't work, but I'm confident it would sweep if the LFO was in order.

I put together an LFO used in the Phaseur Fleur and stuck it in place of the LFO on the Phase 45 and it still doens't phase. Is it that simple as sticking a different LFO in there? Or am I missing something?

[Michael Allen]

Any thoughts on using the Fleur LFO?