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Lamp (light bulb) alternatives

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sleeplessnashadow View Drop Down
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    Posted: Apr 22 2017 at 9:16pm
This is going to be a non technical overview of the lamps (bulbs hereafter) used with the various infrared scopes mounted to the U.S. carbines.

A warning about prices. There are dozens of internet vendors who specialize in obsolete lamps/bulbs. Both used and new old stock. Shop around as prices can vary significantly. EBay is a good source but some EBay sellers have them drop shipped from online retailers who sell them for far less.

Before getting into bulb alternatives there are a few things to consider about all of these bulbs.

General Bulb Construction

All of the bulbs are incandescent bulbs. An inert gas is used inside the bulb to provide pressure inside the bulb. When lit these bulbs get hot.

Bulbs within the Light Assembly were made using a thin glass. They are prone to breakage if dropped. If atmospheric conditions cause the bulbs to be hot on the outside while cold on the inside, or cold on the outside while hot on the inside, the bulbs may burst. Eye protection is recommended when dealing with a bulb not enclosed within the Lamp Assembly.

Operation vs Historical Preservation

Light bulbs have a lifespan measured in hours of use. If you wish to operate any of these bulbs you may want to consider removing the original bulb and using a replacement. This will preserve the original bulb for maintaining an historically correct set of parts. Finding a replacement that is historically correct can be a real challenge as most have been out of production for many years.

Lamp Assembly Bulb for the Model M1 (T120), Model M2 (early & late) and Model M3 Scopes

TM 5-9340, TM 5-9341 and TM 5-9341A are the technical manuals for the Model M1 (T120) and Model M2 infrared scopes. These manuals identify the G.E. #1045 lamp as the bulb used within their Light Assemblies to generate infrared light.

TM 5-9342, TM 5-9342A and TM 5-1090-202-25P are the technical manuals for the Model M3 infrared scopes, Set No. 1, 20,000 volts. These manuals do not identify the bulb used with this model by it's commercial designation. The American Optical part number B-775-35 and U.S. Army part number D8247-28-1 are indicated instead. This was the G.E. #1077 lamp/bulb.

The Light Assemblies of all four infrared models and variations had the same specifications for the bulb they used. The bulbs they were supplied with were interchangeable with the others. The difference was the availability of each lamp/bulb at a given point in time.

The G.E. #1045

      

The bulb has an RP 11 glass envelope with a single contact pre-focus large flange base having 3 unequally spaced slots for connectors. The base/flange is uncoated brass.

      

      

      

The G.E. #1077

      

As with the #1045 this bulb has an RP 11 glass envelope with a single contact pre-focus large flange base having 3 unequally spaced slots for connectors. The base/flange is brass and partially or fully coated.

      

      

      

Replacements for the #1045 & #1077

The following pertains to replacements for both the #1045 and #1077 bulbs as both were interchangeable in the various infrared Light Assemblies used with the U.S. carbines.

The replacement recommended by Sam Bases in Carbine Club newsletter #103 was the #1073 lamp/bulb. This may have been a typo as the #1073 is 12 volts, not 6 volts. He may have been referring to the #1077 used in the M3 scopes. Bases also suggested the #1501 and #1503 as replacements. I've also used the #1007. A more current bulb that is readily available and not as costly is the #1323.

A note about lamps/bulbs with the marking MAZDA. Mazda was a trademarked name registered by General Electric in 1909 for incandescent light bulbs. The name was used from 1909 through 1945 in the U.S.A. This was unrelated to the motor vehicles later made under the same name.

Reticle Bulb for the Model M3 Scopes

The earlier scopes did not utilize a bulb for the reticle. Only the Model M3, Set No. 1, 20,000 volts was designed with a reticle projected from a light.

Technical manuals TM 5-9342, TM 5-9342A and TM 5-1090-202-25P for the Model M3 infrared scopes, Set No. 1, 20,000 volts identify the reticle lamp/bulb as G.E. #328.

      

The #328 is much smaller than the bulbs used with the Light Assembly. The glass is thicker than the larger bulbs with the bulbs less likely to break if dropped. As of the date of this post the #328 is still in production though new old stock is also available at a higher price.

      

      

Replacements for the #328

Sam Bases indicated in Carbine Club newsletter #103 the reticle bulb was the #332. Bases was probably speaking from personal experience without the aid of the manuals we now have available. Bases recommended the #328 as an alternate.

My experience has been consistent with the manuals as the majority of reticle assemblies I've opened have had the #328. As indicated above the #328 is in current production. There are a number of equivalents with one in particular being a standout: the #332. The difference is the #328 and others are rated at a lifespan of 1000 hours. The #332 is rated at a lifespan of 50,000 hours. The demand for the #332 makes them difficult to find. They are in current use in a number of devices with one of the more common being aircraft instrument panels in the cockpits.

Most of us will never reach the lifespan of 1000 hours for the #328. If we do an additional #328 is inexpensive and readily available.

Historical Research Project for the IR Scopes used with the U.S. Carbines

As indicated elsewhere in this thread there is an active research project in progress for these IR scopes and their equipment. This is no easy project. One of the reasons I posted this is to show everyone we're serious and still actively involved with research that includes the electronics used to operate the scopes. There are two of us working this project with the historical research being my primary focus.

Questions regarding the electronics and getting them to work and work safely are not quite ready to be addressed. Please be patient.

I have a couple web pages to update before starting in on the page for the Model T3/M3 carbines which will lead into the pages on the IR equipment. A time estimate isn't yet possible given the amount of time involved in the research, organizing everything, shooting the pictures then authoring the web pages.

In the meantime we could use the help of anyone who owns part or all of one of these IR scope sets if they wouldn't mind sharing information. We can be contacted via a private message sent to us on this forum. An online survey is in the works but taking far longer than I anticipated.

Thanks much

Jim





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welbytwo View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote welbytwo Quote  Post ReplyReply Direct Link To This Post Posted: Apr 22 2017 at 9:54pm
great layout and info--I will look thru my lamp parts
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m1a1fan Quote  Post ReplyReply Direct Link To This Post Posted: Apr 23 2017 at 12:41pm
As always, very well written and chock full of detailed information.

Are there certain bulbs that are harder to find than others, i.e. rare?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sleeplessnashadow Quote  Post ReplyReply Direct Link To This Post Posted: Apr 23 2017 at 6:39pm
Hard to find and rare: The originals.

#1045 for the M1 and M2 scopes
#1077 for the M3 scopes

These lamps/bulbs are old. I tested one of my M3 scope #1077's and it died a bright death. Probably from the introduction of oxygen, says my electrical guru. I think the seal just wore out over time. I haven't been able to find another #1077 in the past month.

I have 3 #1045's I purchased recently for eventual photos and eventual trading. Only wanted one but since their rare I bought all 3 the vendor had. $20 each. Only ones I've seen in the 6 months or so I've been looking.

#1501 and #1503 are fairly easy to come by but watch out for the prices ... shop around. Seen them as high as $10 each and as low as $3 each.

#1007 I bought a half dozen at $5 each. These are the ones I'll use should I ever get a scope working.

#328 is widely available but again, watch out for prices. NOS typically sold at 5-10x the price of new.

I'm not a bulb collector. Bought most only for learning which ones are brightest as ratings aren't always performance with these old ones.

Tried to find an LED replacement for any of the bulbs for the Light Assembly. The brightness from a 30 watt LED would definitely be better than a 30 watt incandescent for putting out the IR light. Was advised by an LED vendor there are no LED equivalents. The bayonet mount has gone the path of history. The mount the bulbs plug into are a shocker: $200 each NOS. Fortunately there's no need to replace them.

The distance and width of the beams is another upcoming test. These 30 watt incandescent bulbs were mostly made for use with auto headlights of the time. The reflector housing helped increase the intensity of the beam as did the design of the headlamp glass. Will be interesting to see if the dark IR lens brightens the beam. Wouldn't think so based on it's flat design.

What increased the distance with the M3 scope over the M1 and M2 scopes was the IR tube, not the incandescent bulbs. The 6032 IR tube was also the reason for the 20,000 volts.

I'm leaving the electrical part of everything to Dan. Been sending him various items I've come across that people have concocted to get the power packs working.

To add an historical perspective ... The M1/T120 and M2 scopes were specifically designed for jungle warfare at night. Close quarters combat. Found several Corps of Engineers documents explaining the reason for their existence being consistent with their performance. The late M2 scopes appear to have been an attempt to meet an immediate demand with Korea but also realizing they were woefully inadequate for the distances common in Korea. The late M2's simply filled a gap while the M3's were being developed. The demand for replacing the M2's with M3's was a constant in Korea. As were the demands for the power racks for the M3's.

Jim
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m1a1fan Quote  Post ReplyReply Direct Link To This Post Posted: Apr 23 2017 at 10:38pm
Are there any records stating how many bulbs of the different types were produced? Speculating that more were produced than needed for spare parts. Can't imagine how much fun it would be to test out a scoped carbine years after the fact.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 23 2017 at 11:10pm
bulbs were a common source item, as mentioned above, they were car headlight bulbs of the time.
Basically the different numbers were do to different wattages. New designed bulbs were brighter or more resistant to burn out.
These type bulbs were available in 12 volt and duel filament bulbs which would give high/low beams.
The base is also designed to orientate the filament so the light beam was horizontal so as to aim the light on the road. Same should be true for the scopes.
Anyone who ever owned a 6 volt car would tell you at idle you were lucky to see 10 feet. As the car sped up lights would brighten due to the voltage increase of the generator to about 8 volts. If your regulator was on the fritz and you nailed the gas your lights would burn out due to the voltage!
 
the death of these were the advent of sealed beam bulbs.
 
The 328 bulbs were common mini flashlight bulbs as well as instrument panel lights. These were in common use and still made today.
So numbers produced were in the millions, and not for specific supply of scopes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sleeplessnashadow Quote  Post ReplyReply Direct Link To This Post Posted: May 18 2017 at 8:34am
Part II - Lamps & Alternatives

In my first post I identified the two primary bulbs originally used with the IR lights as the GE #1045 for the M1/T120, early M2 and late M2 with the GE #1077 for the 20,000 volt Set No. 1 containing the Model M3 scope. I also discussed alternatives based on suggestions by others more knowledgeable than myself.

Since that time I have acquired the alternatives and run comparison tests. I've also sought the input of someone who collects and sells obsolete bulbs. What follows is what has been learned.

The tests were conducted with multiple examples of each bulb type.

The IR viewer used to detect the IR beams was a Sony Model DCR-PC5 Handycam capable of IR viewing. It's IR light was covered during the tests. A working M2 or M3 scope was not available. The original IR image tubes may or may not have better sensitivity than the one used by Sony. For this reason the bulbs were tested both with and without the GI infrared filter covering the GI lamp and it's reflector.

The IR filter used was clean and as new. Each bulb was tested with both a clean gold reflector and a clean silver reflector. The color of the reflector did not appear to make much of a difference.

Alternatives to the #1045 and #1077

#1501 and #1503

Beams are focused to the center. Brightness is roughly 1/5th of the #1045 & #1047. No noticeable output difference between the #1501 and #1503. The #1501 being current production can be purchased at under $4 each new.

#1007

Contrary to the information listed describing this bulb the beam is not focused on the center. It radiates in a circle around a center black hole. Brightness is about equivalent to the #1045 and #1077. Cost varies between $6 - $20 each.

#1073

This bulb is a 12 volt bulb and not for use with the 6 volt light assemblies.

The #1045 and #1077

These two bulbs appear to be equal in output. Beams are center focused and bright enough to throw the unfiltered beam a distance of at least 150'.

The filtered beams were not detectable beyond 50' leading me to the conclusion the original IR tubes are more sensitive than the Sony tube. The Type 6032 tube used with the Model M3 scope and operating at 20,000 volts would clearly be the better choice. As was experienced and requested by those who used them during the war in Korea.

Input from Don at DonsBulbs.com

The question posed to Don was for possible alternatives to the #1045 and #1077. He was advised of the above alternatives that proved to be poor alternatives.

"Basically none of these bulbs can be substituted for other bulbs. These bulbs were designed for highly critical specific use.   Any substitution attempts will be sub-par, like much dimmer, etc..."

"I know of no suppliers today for the #1077. I haven’t seen any of these in the market for over 20 years. Any search for these will likely be unsuccessful."

"As of last year, I knew of a supplier who had some #1045, pricing at that time was offered to me at $200 per bulb."

Regards, - Don Schnapp

"Alternative" Semantics

The 6 volt bulbs discussed above have the following things in common:

  • Incandescent Lamps

  • +/- 6 volts

  • +/- 5 amps

  • Base: single contact, pre-focused, flanged

  • Glass: RP11

The flanged base is unique and non-negotiable given the mount it attaches too. Of the various bulbs that have this base the one thing that makes the above "alternatives" is they simply fit the mount attached to the reflector and operate at about the specs the light assembly was designed for.

So these alternatives are alternative bulbs that will fit and function. They are not alternatives that will perform as the originals did.

Performance Alternatives

Other than the original #1045 and #1077 there do not appear to be any performance alternatives. The cost of these if you can even find them would make most people inclined not to use them in fear of breakage or reaching the end of their lifespan.

While an LED bulb would be one of the best possible options for cost, performance, lifespan and replacement no LED bulb has yet been designed with the flanged base required to mount the bulb to the light assembly.

Possible Options for Operation

To preserve the historical value and provenance of the IR light assemblies and the original bulbs they used it would probably be wise not to use them to operate a working IR scope.

Perhaps the best alternative would be an IR emitting light of a more modern design. Possibly constructed as a replica of the original.

Unless some light bulb guru can come up with an adapter for plugging an appropriate spec LED bulb into the correct salvaged flange base mount having a single contact.

Jim
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