Phase 45 debug (LFO not working)

Started by jlullo, November 04, 2007, 06:45:03 PM

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jlullo

Hey guys,
I built a phase 45 using the tonepad layout.  I bought a matched set of 2N5952's from another member here on the board.  When engaged, the effect won't oscillate, but i can hear all of the different frequencies when turning the trimpot.  I had to reverse my transistors' orientation in respect to the layout to get any sort of phase sound, so i'm assuming they are correctly positioned.  Since the transistors and IC's aren't numbered on the layout, Q1 and IC1 will be the ones on the left and Q2 and IC2 will be on the right.  Here are my readings:

Q1
D 4.26
S 4.26
G 1.97

Q2
D 4.24
S 4.24
G 1.96

IC1
1 4.26
2 4.26
3 4.24
4 0
5 0
6 4.26
7 4.26
8 8.97

IC2
1 8.30
2 3.23
3 5.72
4 0
5 4.25
6 4.25
7 4.25
8 8.97



mdh

This is more or less a shot in the dark, but you might check for a solder bridge somewhere in the LFO, or where the wires from the speed pot connect to the board.  I say this because it happened to me when moving a Phase 90 from my test rig to its final box... I got a little sloppy with the soldering, and a solder bridge killed the LFO.  It would be quite an easy fix if that's your problem, but I must admit I didn't look at your voltages  :icon_redface:

oldrocker

Not a phaser but when building the Heartthrob Temolo earlier today the oscillation wouldn't work since there was a cold solder joint in the oscillation section.

PerroGrande

Pin 5 of IC1 is worrisome -- showing 0v.  Are you sure of that reading (I ask because it is very close to pin4)?  I would not expect it to be 0v.  If the reading is accurate, I would recommend checking for shorts/solder problems in that area of the circuit as a starting point.

jlullo

thank you so much for the help guys... i checked it over and had two electros backwards  :P  stupid me!   works great now!


thanks again