Paolo,
It might work, but I would not have gone that route. Injecting high
voltage RF into the circuit could easily damage the integrated circuits
on the board, thus ruining any change of getting the meter to operate as
originally intended.
Dave
On 2/15/2016 4:11 PM, Paolo Cravero wrote:
Thank you Dave and John.
I triple checked my measurements, and ABCD of that transformer are in
series. AD is the arithmetical sum of the three values I wrote earlier
today. As well as AC is a sum and BD too.
Weird, but since I have no diagram whatsoever of the General Microwave 475B
power meter I
John,
Yep, You're right. That sounds entirely plausible. Didn't think of that.
Dave
On 2/14/2016 2:03 PM, John Rehwinkel wrote:
I'm not sure what the A-C windings do -- they have a 0.`6 ohms ratio to the B-C
pair. With 120 VAC input, that would give you 19 volts, not line isolated.
Not
> I'm not sure what the A-C windings do -- they have a 0.`6 ohms ratio to the
> B-C pair. With 120 VAC input, that would give you 19 volts, not line
> isolated. Not sure what design purpose that would serve. 19 volts is not a
> standard input voltage, like 12 or 24 VAC that could conceivably
> I measured DC resistance of the transformer four input pins, those that go
> straight to the card connector and here is the result:
> AB 58 ohm
> BC 358 ohm
> CD 712 ohm
>
>
Looks like CD is the whole primary and BC is half of it. I'd measure AD and AC
too.
- John
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Paolo,
A variable AC transformer (Variac, Powerstat, and many others) is a
pretty basic piece of electrical test equipment, like wire cutters and a
screw driver. It's hard to do any sort of interesting electrical
experimentation without one. They can often be found on eBay
(expensive), or
Looks very like a Sperry SP-356 Panaplex display...
Nick
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Paolo,
Look at the power input pins on the transformer. If it was designed for
120/240 volt operation, it should have 2 primary windings. They would
be connected in parallel for 120 VAC operation, and series for 240 VAC
operation. For 240 volt operation, the two center pins of the group of
Paolo,
It should be relatively easy to trace the circuit from the power
transformer input pins to the card edge connectors. I would apply AC
power through a variable AC autotransformer(e. g. Variac) to those two
pins until you reach 120 VAC. The display should start to light by
then.
Thank you Dave for the excellent walkthrough procedure.
It was used in a 220 VAC country and the input side of the transformer
looks like it has 4 pins. Looks like...
Anyway, the original device most probably was a General Microwave Power
Meter 475B. The online picture from an auction looks
> I have been given a Gralex Industries 475B-10 panel meter. It mounts a
> Beckman SP-352 panaplex 4 digit display and I would really like to light it
> up as-is since it even contains AC transformer.
Nice!
> Any chance someone knows how to wire it up, and what kind of meter it is? It
> comes
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