Sencore MU150 Continental Ii

[ca7922303]

Looks like Grid Leakage, Dynamic Mutual Conductance, Life test, and GM test button functions not working on this tube tester.

[Jon Snell]

It can't be much as it is a very simple machine.
Have you checked T2 for output?

[ca7922303]

It can't be much as it is a very simple machine.
Have you checked T2 for output?

Here some photos. Not sure of test points.

[nosaj]

I just repaired a TT-1 Heathkit. Gm function would work on it either. Turns out the 2 tubes in it were worn and wouldn't oscillate for gm test. The switches may need to be worked some also.
nosaj

[ca7922303]

It can't be much as it is a very simple machine.
Have you checked T2 for output?

T2 leads going to Filament(A) switch, not reading per schematic. OB2 tube not lit(cold). 12AU7 is lit.

[Jon Snell]

OB2 is a cold cathode regulator and lights when the threshold is reached. I would hazard a guess, T2 & T3 are not being powered up. (8.2v zener has no voltage to supply the transistors).

[ca7922303]

OB2 is a cold cathode regulator and lights when the threshold is reached. I would hazard a guess, T2 & T3 are not being powered up. (8.2v zener has no voltage to supply the transistors).

These two (2) diodes measure ((-)mvdc) and (.258v) diode test.

[nosaj]

These two (2) diodes measure ((-)mvdc) and (.258v) diode test.

With one leg lifted?
nosaj

[Jon Snell]

Germanium diodes measure abount 0.25v one way and almost infinity the other.
If they are CR9 & CT10 then they allow the multivibrator to trigger.

Check you have 8volts across the zener. CR11

[ca7922303]

With one leg lifted?
nosaj

No, measured in circuit.

[ca7922303]

Germanium diodes measure abount 0.25v one way and almost infinity the other.
If they are CR9 & CT10 then they allow the multivibrator to trigger.

Check you have 8volts across the zener. CR11

Yes, the board is stamped CR9/CR10. Getting ((-)mvdc) across CR11.

[Jon Snell]

With no voltage across either, the transistors are no oscillating.
8 volts on the supply?
Check the main power on the anode of the OB2, if no voltege, check the switch contacts and supply to the switch and follow the circuit back until you find the AC power from the transformer.
One of those is missing.
Discover which one and repair it.

[ca7922303]

Looks like Grid Leakage, Dynamic Mutual Conductance, Life test, and GM test button functions not working on this tube tester.

Correction: Shorts, Gm-Emission, Grid Leakage functions work. Dynamic Mutual Conductance function does not due to Gm Test switch broken. Need to know where to get that Gm Test switch from?

[nosaj]

Lets have a picture of it. The backside.
nosaj

[ca7922303]

Lets have a picture of it. The backside.
nosaj

Backside of the Gm Test switch? There are photos in this post of board and front of unit.