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Old 15th Oct 2018, 6:37 am   #2
Dekatron
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Join Date: May 2009
Location: Linkoping, Sweden
Posts: 1,463
Default Re: AVO CT160.......dancing meter during TEST

Hi, welcome to the forum!

You should start by reading this article, it explains how a noisy contact on the gm wheel was troubling the writer: http://www.jacmusic.com/Tube-testers...0-1/index.html , he also says that he had a noisy wiper contact on the Grid Volts (Vg) potentiometer.

Before removing the switch mentioned above you should note its position so that you can get it back in the same position afterwards as it sits on the shaft of the gm-wheel potentiometer (I know of at least one situation where the switch had been turned upside down (!) and not working as intended).

You should also check the two Anode current controls for noisy wiper contacts and switch contacts.

Start by checking these things and let us know what results you find/get when cleaning them.

High contact resistance due to dirty/corroded contacts is quite common in these testers and since some currents are very low (microampere and below) high contact resistance results in high voltage drops (several millivolts up to several volts which shows on the meter).
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