Edge lit displays identification help needed

[Tomasz Kowalczyk]

Hi, I've recently came across two sets of edge lit displays. They weren't hard to figure how to power them up, however I'd like to know more about them - I always like to have a datasheet of something I own. The problem is there isn't much written on them.

Both types are powered up with 28V, 40mA bulbs. I found that ML387 (link below) are compatible with original - which was crucial, as about 10-20% of original bulbs were not working.

https://www.tme.eu/gb/details/lamp-ml387/light-sources-lighting/brightmaster/

There are two types - first one is a bit bigger and has bent acrylic lightguides, with all the bulbs being hidden in the back. On the piece of PCB in the back there is written KGM M18, which leads me to conclusion, that it is a part of series already known to the internet and its full name would be: KGM Multi-Indicator Type M18. I cannot be sure, though.

They can display numbers from 0 to 9.

The second type is much smaller - that's because the lightguides are not bent at all, which greatly cuts space needed. There isn't much I can guess about their name, though - on few of them there is written HARWIN on the side and thats all I know for now. They are also pain in the ass to put back together after disassembling.

They can display numbers 0 to 9 and also a left hand dot and right hand decimal point.

So, does anyone know more about them? Every bit of information will be useful to me. 

[Dave ZL3FJ]

I think the KGM unit is very like the displays used in the GR 1123A synchronometer- I will check my manual tomorrow. It may actually be the same. I am  particularly interested in the ‘equivalent’ bulb type- I need some!

DaveB, NZ

PS – just rememberd- these are why I originally joined the group! Here’s my 2006 post-

 

“Looking for information on the IND-1803 Numerik Indicator.

This is an old and unusual numeric display device that was used by GR (General Radio) in some instruments  they produced in the late 1960s/early 1970s.  These devices were made in England by KGM Electronics Ltd (No idea who they are) for GR.

The device uses an array of small incandesent lamps, of the type that was often found in instrument panels, pre-LEDs, and has a lamp per displayed digit (0-9) plus two more for the right hand and left hand side decimal points. The lamps are of course all replaceable by extraction from the rear of the module.  Inside these things there's a multiple lightpipe arrangement that I dont know details of (not been game to open one up-yet!) that transfers the light from the illuminated lamp to a well formed digit near the front that is made up of multiple dots of light. The digits are layered in much the same manner as the multiple cathodes in a nixie.  The whole thing is designed to clip into a 'socket' that has a spring loaded contact for each lamps centre contact plus a common one for the metal base plate the lamps are mounted on at the back of the module. The module itself is approx 60mm high, 55 mm deep and 25 mm wide-i.e. roughly an inch of display width per digit.

I'l organise some pictures of these things in a day or so, but I'm interested to find out more about the devlopment and other background to these rather unusual display devices. If anyone can give me more info on these things or point me to a source of same I'd appreciate it.”

 

So it’s not the same but very similar. I got 2 replys back then! Text follows-

*****

Info on their history and development is scarce, but we have photos of several different styles here in our Photos section:

<http://ph.groups.yahoo.com/group/NEONIXIE-L/photos/browse/2b13>

 

(I still need to figure out what to do about the last couple of pages of albums - should I do some more consolidating, or just clean up the titles to make them more readable but leave them basically as-is?)

 

A.J.

 

Those are edge-lit readouts.  Here are a couple photos of the IND-0300:

 

http://home.comcast.net/~cwebster68/edgelit1.jpg

http://home.comcast.net/~cwebster68/edgelit2.jpg

 

 

- Chris W.

***

 

Dave Brown

Christchurch, NZ

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[seaforth23]

Hi, I have two KGM displays, type M3. I fitted LED's in place of the filament bulbs - in this case cyan. I don't know much else about them.

[Tomasz Kowalczyk]

Thanks for information! Do you still own the synchrometer? Would you like to share a photo?
The ML387 bulbs seem to be drop in replacements. I've looked at them through macro lenses and measured outside dimensions - it is exact copy. There is only one, very slight difference - one of the leads, the one on back end of the bulb is rounded, while original ones seem to have it a little bit squashed. It might affect indicators in which the bulb isn't held through a spring contact, but in my M18 type it is not a problem.
 Original bulbs have indication on them and it reads: GI727 28V 40mA. I think I saw some other replacement types from other distributors, but as I use mainly TME I just slipped few experimental bulbs into regular order. Right now I have 50 of those and hopefully they will last for some time!
After replacing the damaged bulbs I can't notice a difference between original and new. 

[Nigel Tout]

Similar displays are used in the Canon Canola 130S desktop electronic calculator from about 1968.

This is shown on the page http://vintagecalculators.com/html/canon_canola_130s.html

 

At the bottom of that page are photographs of another version from KGM which is marked M4 and may be larger than the M18 already shown.  Many years ago I saved this from a box of old components at the company where I worked at the time.

On the side of the M4 is ‘British Patent 847972’.

This patent can be viewed at https://worldwide.espacenet.com/publicationDetails/biblio?CC=GB&NR=847972&KC=&FT=E&locale=en_EP .

Click on ‘Original document’ in the list at top left to see the original patent document.

 

Regards,

Nigel Tout

 

The second type is much smaller - that's because the lightguides are not bent at all, which greatly cuts space needed. There isn't much I can guess about their name, though - on few of them there is written HARWIN on the side and thats all I know for now. They are also pain in the ass to put back together after disassembling.

They can display numbers 0 to 9 and also a left hand dot and right hand decimal point.

 

 

 

So, does anyone know more about them? Every bit of information will be useful to me. 

 

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[petehand]

The smaller one is made in England. I picked up a 1960s DVM that had five of them at a government surplus auction.They were driven by stepping switches.

I also have some that were made in Japan, by Stanley Electric Co in about 1970. These are not numeric. They have images.