Old Merc-O-Tronic

[Tom]

I have an old Merc-O-Tronic that I’m bringing back to life. It’s the one with the motor and points in it, not the vibrator tube. All is good except for the condenser capacity test. The needle pegs when I press the test button, with a good condenser in line.

The leakage test works fine, which tells me the transformer is good.

I assume there is a capacitance bridge in there somewhere, with a capacitor as a reference. Can anyone confirm this? Also, is the reference capacitor the pair of black cubes wedged under the transformer?

Thanks for any help you can give.

Tom Manley

[debe]

There is very little in the Capacity test. See circuit which has been drawn in red for the relavent part of the test. Check the transformer puts out 6.3V. R6 is ok & the bridge rectifier. If you want full explination of the circuit google Mercotronic patent, that’s where the circuit diagram came from.

[Tom]

Whoa, that’s great! Thanks for the diagram and the suggestions.

I have some tracing to do. I’ll assume it’s the rectifier, since that component is used in this test only. Already getting the voltage from the xformer. Resistor I easy to check.

Tom

[Author]

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