Hastings Vacuum Gauge VT-4B modern part

Is that a varistor or non-polarised transient suppressor of 130V rating?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

No clue. The original is history, the customer plugged the unit into

230V. No way to see any case markings or even physical dimentions of the original.

Thanks, Steve

I don't know exactly what technology that is, but it's function is a surge suppressor. The unit will run if that part is removed. Whether anything else has been damaged, only way to know is to try it. I'd suggest checking D1, D2, C1, and R3. If they are good (or after replacing whatever isn't!), try it without D3.

130 V may be a bit close to 125 VAC, maybe 140 or 150 V? Replace with modern device and add a fuse while you're at it. :) With the fuse, even if D3 isn't replaced with anything, a surge or plugging into 230 VAC shouldn't result in damage beyond D1 in any case.

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Not this time, it isn't a surge suppressor. This unit uses the varistor as a pre-regulator of the AC input, and it might be intended to conduct even in the absence of a surge. The part number was probably V130 LA1 (the LA series was from Panasonic); modern equivalent seems to be ERZ-V27D201.

Radio Shack part #206-568 is close enough

That's interesting. It would indeed, though the unit would still work without it on 115 VAC, but with slightly worse regulation and R3 would get a bit toastier than normal.

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Thanks for the input everyone. Mouser sells the V130LA1's by Littelfuse, should do the trick I hope.

On a different note, the customer also sent in a newer unit, blown up the same way. It has the same model number, but different board. Looks like it uses 3 terminal regulators & an op amp for its circuit. Both filter caps pre-regulators exploded, hopefully not taking out everything else down circuit with the massive ac ripple that likely followed. That one comes next though.

Steve

What sort of output is to be expected on this type of unit? I'm getting somewhere around .5VRMS @ 600Hz square wave. I think it's proper, but I don't know much about these gauges.

Thanks, Steve

I'm not positive but the voltage sounds about right and the frequency isn't critical. The spec for the VT-4 is 320 mV AC. But that's loaded with the TC tube.

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