Problem with signal generator

[Helmholtz]

Please let me know if the Q101 gate voltage is positive or negative.

[caesparza]

Hi Helmholtz,

With the volume control at 12 o clock.

The voltage changes according to the range selector as this:

X1: -0.044
X10: 0.384 steady.
X100: moves randomly between 0.264 and 0.612
X1K: moves ramdonly between 0.495 and 0.694.

[Helmholtz]

Have you checked VC101 for leakage (Ohmmeter)? Might have some conductive dirt between its plates.
The Wien bridge is a very high impedance circuit which is easily upset by a tiny leakage.

[caesparza]

I don't know exactly how to do the check. What I'm looking for with the ohmmeter? What can I use to clean that kind of component?

Thanks.

[Helmholtz]

I don't know exactly how to do the check. What I'm looking for with the ohmmeter? What can I use to clean that kind of component?

Should measure open with Ohmmeter.

If not, clean with tuner spray and /or compressed air. Make sure plates are not bent causing a short.

[caesparza]

I attached some photos of the VC101 component. The underside photo has the terminals indicated with A, B, C and D. and F for V102. It's not very clear from the schematic the connections to me, sorry about that.

I'm assuming that V101B is the one with the terminal connected with the black wire to ground (terminals A-B), V101A is connected to the range selector and V102 (terminals C-D). Both read 0 ohms.
F is V102. Terminals A and D are not connected to anything.

The pieces look in very good shape and to my eyes totally straight, no bent plates.

Is that information useful?

[caesparza]

Helmholtz, its back to life!!. I cleaned the components with a high power air vacuum and the unit is giving a sine wave I checked with a little amp, but I'll scope the thing in the afternoon. Right now I need to go to run some errands.

I really want to thank you for the time and interest you put in the case. I feel really good, you have made a happy man. It's been a really interesting and learning experience to check this unit, very different from the tube amps I check.

Thanks again mate.

[Helmholtz]

There are fixed "stator" and rotatable "rotor" plates. There should be infinite resistance between the two.
Just see how they are connected in circuit. There must be no continuity (infinite resistance) between upper and lower connections in the schematic.