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Old 5th Feb 2019, 8:43 pm   #19
Cathode Ray
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Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
Default Re: Marconi Valve Voltmeter TF1041C - repair thread

Anyone good with valve voltage regulators?

As an experiment I decided to remove a valve (12AT7) from the main meter to reduce current drawn and see if the regulator remained at 220v output.

Well it did'nt!
The output went up to 360v, with a 500V input voltage.

The main meter was still drawing some current as I had only removed the main bridge valve but left the other valve in place.

I found an articles on Series Double Triode Voltage Regulator which appear similar to the diagram attached above.
https://electronicspost.com/series-d...age-regulator/
This shows how the circuit works, and it should regulate the voltage.

The 12HB7 is an expensive valve and I don't want to replace it unless absolutely necessary.

Appreciate any input you guys may have.
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Ray
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