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. Using an isolation transformer in series with the power input
will make probing the board safer.
You might look at the PC board to see if there is a switch or wire
jumper for 240 volt operation, but that should be readily apparent.
Once you have the display lit, you can check the remaining terminals for
any output voltages. Terminals that do not have output voltages are
candidates for inputs. usually, the + and - inputs will be on adjacent
terminals.
I would apply millivolt level DC signals (derived from a resistive
voltage divider across a 9 volt battery) across various pins until you
get a reading on the display.
I have used this technique successfully many times to figure the pinouts
on old, undocumented digital panel meters.
Dave
On 2/11/2016 5:37 AM, Paolo Cravero wrote:
Hello John.
I asked the person who gave me the panel meter to trace its source
bolometer: if the chassis has not been thrown away I should get the
info one of these days. Through this "channel" came some TIL3xx
displays and few red and green Philips ZM1020 nixies.
I also wrote an email to the current Gralex but got no answer. Which
is positive, since it is not a negative answer.
I share few pictures of the device. I can open up the PCB sandwitch
and begin tracing what goes where. But first I would like to make sure
the panaplex display is still working, and I should do it wirelessy as
with Nixies with a HVAC source (like a laptop CCFL driver).
I will write back when I have further updates.
Paolo
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