Keithley 153 Microvolt Ammeter Tube 1966

[@jonscally2349]

nice old meter,be worth a restoration,would love to have that on my workbench.

[@sapphiresphone7144]

It's great to see the triax connector. I've never found an affordable source for the male end.

[@mikefinn2101]

Great restoration project. Was very expensive meter in 60s very rare.t riaxial cable was used. 73s wb7qxu

[@migsvensurfing6310]

You could build a small independent 1,5v power supply instead of the batteries. Strange how the dial paint is only aafected in the area directly under the glass. The rest of the suface is in perfect condition. Thanks for the video.

[@LutzSchafer]

Looks like the Varta cell is loaded with 5 uA. This is a mercury cell used in old SLR cameras and has nominal 1.5 V

[@ivolol]

I'm guessing some caps need replacing... after almost 60 years? Maybe some carbon comp resistors...Awesome piece of equipment history. Chopper amp way before you could buy one in a tiny little convenient SOIC8 package. Should be awesome as a nullmeter. Would be cool to see it fully restored, maybe you'd add a switch that connects / disconnects the lines from both batteries into their circuit connections

[@TeardownOZ2CPU]

i thinks it is CRASY those two coin cells are not diconnected when power is off, maybe via relays ?? or such, i am not super happy about hidden cells like that

[@craigs5212]

That old mercury cell was used in a lot of camera light meters, mercury cells have a flat discharge curve but are now banned. At about 7uA discharge from your measured 196K ohm load I would guess the life of the cell would be about 5 years. Likely it would have be replaced at calibration or when the zero quit working. I couldn't find a data sheet on the original cell but I would guess the cell capacity was in the range of 200mAh.

[@alistairmackintosh9412]

v 625 px = mercury oxide/zinc cell. extremely flat discharge curve.