How to make the old style 727 transponder work? .. help.

[Geremy Britton]

Hi all, Probably a question suited to Gwyn or Mike but if anyone knows from the pics below that will help how to get the panel to light up. I'm presuming it's a lightplate from the look of the lettering at close viewing and the number of pins on the back.

I've looked at some schematics of similar panels but no joy.

If someone could tell me which pins make it light and what voltage to apply that would make the panel look awesome

Thanks in advance!

[Jackpilot]

NO pic

Usually you have to open it and find the wires behind the lightplate. Try 5V.

[Geremy Britton]

Sorry, realised after i just submitted. Was attaching them as you posted the comment. Any ideas?

[Jackpilot]

29 NEG 34 POS 28V

(Mine is Gables p/n G1492-03, Nov 1987....at your own risks, but it should work.)

[Michael Carter]

I have two similar Gables units. They at 28VDC. A lot of Gables equipment is.

[Jackpilot]

I was wondering if the bulbs are 28V, I doubt it
In which case there should be a way to feed the 5V

There should'nt be polarity either

Mike?? pretty sure you already opened their guts!

[Jackpilot]

Gez..did you check it?

[Geremy Britton]

Seen as it's been a working weekend for me then i haven't. My power applicator is at the workshop so next time i'm down there i will test it (I can't wait!) I'll just work my way up from 5v to 28v. And we should be good.

I'll let you know in the next couple of says and i'll post some pictures of it backlit - With a bit of luck!

Thanks lads.

[Geremy Britton]

It works! 29 NEG 34 POS @ 24 Volts.

You get a nice smooth dim glow from the panel.
And my xponder is Nov. 1974 Gables.

Thanks very much

I'll take a picture tonight and show you it working. It's just at the moment holding the the panel, applying 2 wires to the necessary pins which are less than 2mm apart not touching any others. Oh and actually looking at the panel itself to see if it works can be rather difficult with 2 hands.

I'll get an extra pair of hands tonight to take a picture for me.

I would have never of known which pins to apply voltage, and the combinations you could have with 34 pins i'm sure will have had me at my desk for years. LOL

[Michael Carter]

Usually, but not always, the pins for the backlighting are the center pin and one of the ajacent pins.

On the Collins 611 flight director controller I had to call a shop in Memphis to get the correct pins. They were way on the outer perimeter of the jack. Pin 23 & 24 IIRC.

Roll pins with wire soldered to them or crimped was good connectors for individual pins.