Help with wiring for Gralex panel meter (with panaplex display)

[Paolo Cravero]

Hello.

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.

Any chance someone knows how to wire it up, and what kind of meter it is? It comes from a bolometer, so most likely it is a voltage meter. Unfortunately, unlikely other Gralex devices whose pictures I could locate online, this unit does not carry a sticker with the pinout of the backside connectors.

Thanks,

Paolo

[John Rehwinkel]

> 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 from a bolometer, so most likely it is a voltage meter.

Most panel meters are. Do you have access to the rest of the bolometer?

> Unfortunately, unlikely other Gralex devices whose pictures I could locate online, this unit does not carry a sticker with the pinout of the backside connectors.

If not, your best bet is probably to open it up and see if you can trace out the circuit. We can help with that if you like.

- John

[Paolo Cravero]

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

[David Speck MD]

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

[Paolo Cravero]

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 pretty much like the panel meter I've got.

Off to look for some kind of documentation... it's easier to look up online during few spare moments than reverse engineer a PCB in a hurry.

Paolo

[alb...@sympatico.ca]

Hi  it looks like a standard Sperry panaplex display  - any idea of the model number - perhaps Dieter has it on his database. The display looks great and will probably work fine. You could consider de-soldering it using one of those low-melting solders as an aid to safe removal
Good luck
 

---

Date: Thu, 11 Feb 2016 11:37:27 +0100
Subject: Re: [neonixie-l] Help with wiring for Gralex panel meter (with panaplex display)
From: paolo....@gmail.com
To: neoni...@googlegroups.com

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[David Speck MD]

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
4 will probably be connected.

No harm would be done if you supply 120 VAC to a meter wired for 240.
However, the other way around would destroy in in an instant.

Deciphering it your self will take a lot less time than trying to find
specs on obsolete components. It may have even been an OEM component
that was re-badged with the microwave meter's manufacturer's name. In
that case, finding any docs would be nearly impossible.

I have boxes of old Analogic DPMs that I can no longer find data for.
They have been relatively easy to figure out. This one should be, as well.

Dave

[Nick]

Looks very like a Sperry SP-356 Panaplex display (I'd put money on that being the one)... is it socketed?

Nick

[Paolo Cravero]

I am back with some data.

The panaplex is a Beckman sp-356 indeed (see picture), but I would rather leave it mounted.

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

Unfortunately nothing indicates the dual supply trick Dave mentioned.

Now I need to find a way to obtain 120Vac from European mains. Perhaps a 220/12 chained to 24/220? Needless to say I do not own a variometer (yet :-) ).

Paolo

[John Rehwinkel]

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

[David Speck MD]

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 for much less at amateur radio swap meets (Hamfests).
Hamfests are usually the best place to find such useful equipment, if
you can locate one close by.

Your arrangement with the two chained transformers will indeed give you
120 VAC, with the added benefit of mains isolation.

I would check the resistance from A-C and A-D as Neon John recommended.
If there are no surprises, I would apply 120 VAC to pins C- D. If the
meter lights, you are done. If nothing happens, you could apply 120 VAC
to pins B - C.

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 be used.

Dave

[Paolo Cravero]

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 cannot reconstruct anything. The two PCBs of the meter have logic chips, a BCD to 7 segment decoder, few IL74 optocouplers, LM339's, NE555.

I will look for a variometer at the next ham swap meet in mid April. That's where 1 year ago I started my journey into the Nixie & C. world with 4x B5092 and 1x B5094. Before that I struggling going from 5Vdc to 3.3Vdc of other projects, and now I'm into HVAC (yes, I should know the safety rules <g>).

In the meantime I will check my junkbox for a suitable transformer to build a step-down chain.

Paolo

[John Rehwinkel]

> 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 be used.

That may be a tap for Japanese (100 volt) power.

- John

[David Speck MD]

John,

Yep, You're right.  That sounds entirely plausible.  Didn't think of that.

Dave

[Paolo Cravero]

Good point on the Japanese input. Interesting how it happens to be in a US made device located in the European land :)

Anyway I am afraid my first journey into panaplex is already over. Tonight I used a CCFL driver circuit to test wirelessly some zm1020 nixies and I also tried the panaplex: no sign of gas from it while a picture on ferrotronix website shows it should glow. If it is still working I should get a glow, shouldn't I?

Paolo

[David Speck MD]

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

[Paolo Cravero]

Wait, Dave. I did not inject RF into the circuit. I would never do that. Not with a direct connection.

I did what I show in this video: https://www.youtube.com/watch?v=BacMcJt9Kv4 with the difference that the wire touched the panaplex glass. Does it count as injecting HV RF? Some RF could have been induced into the whole circuit, but I wouldn't say that the level is dangerous for that kind of electronics. Or the HV RF induced a high voltage on the display pins that then obviously goes back to the meter circuitry...

Mmmmhh, a panaplex has the anode immersed into the front glass, so it is pretty close to the HV RF source. Then probably my test induced HV into the circuit.

At least now the topic is back to dislpays rather than panel meters :-) And I still have to build that step-down AC transformer 220V to 110V or so.

Paolo

[Gralex Ind]

Hi, 

I'm sorry for inconveniences on the website.

We have all the technical information, parts and knowledge about Gralex meters.

If you like contact directly the expert on this technology please use in...@gralexindustries.com or Ph. 203 681 9615

Thank you

Johnny Realpe

Managing Partner

Gralex Industries

[Paolo Cravero]

On Wed, Feb 24, 2016 at 7:36 PM, Gralex Ind wrote:

 

I'm sorry for inconveniences on the website.

We have all the technical information, parts and knowledge about Gralex meters.

If you like contact directly the expert on this technology please use info@gralex....

 ...

Johnny Realpe

I did as suggested Mr. Realpe, wrote an email, but got no reply yet.

I will continue to reverse engineer the panel meter until I come up with something meaningful: that's part of the fun in my hobby. Meanwhile I have assembled an 80Vac transformer, and nothing moves. Next experiment will be to make up a test point where there should be a known voltage, like across a TTL IC and expecting 5Vdc, and feed some AC at the transformer input.

Good luck with your business,

Paolo

Questa e-mail è stata inviata da un computer privo di virus protetto da Avast. www.avast.com

[Gralex Ind]

Paolo,

Take us a week found this product, is really old.

We attach pictures of the wire connections for this meter.

Thank you 

Johnny Realpe 

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[Gralex Ind]

Thank you

Johnny

On Tuesday, February 9, 2016 at 3:37:39 AM UTC-5, Paolo Cravero wrote:

[Paolo Cravero]

THANK YOU Johnny!! The meter lives again! My first Panaplex.

When it powers up the display starts counting at a constant pace up to 3999 when it turns into four dashes. I have not applied an input signal whatsoever, and it looks like a capacitor that is slowly charging. Now I am going to buy a proper female card connector and plan a way to use the four digits (a 24h clock does fit, yes, but it depends on the input signal requirements).

Dave, I would have never figured out this wiring scheme without the original scheme. Would you?

Happy Paolo