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Author Topic: Lamp life
Michael Dixon
Junior
Posts: 29
From: East Bend, NC, USA
Registered: Nov 2009


 - posted November 28, 2009 07:55 AM      Profile for Michael Dixon   Email Michael Dixon   Send New Private Message       Edit/Delete Post 
Apologies if this is an already overworked topic. My Sears 3.9288 std.8 projector, purchased new in 1963, has never required any repair and still runs very well. The DLS lamp is not low cost. One online USA source has the price over $120.00 each, but other sources are available at lower cost. 30 or more years ago, a magazine article showed how to use a double-throw switch and a thermistor to gradually warm up the lamp before going to full voltage/brightness. I made this modification to this projector with good results. I do not recall the exact thermistor used. As most already know, an incandescent lamp has very low resistance when cold. The immediate current (amperage) inrush when energized is considerably greater than the normal operating current and is brutal to the lamp filament. Burnouts often occur at startup. The thermistor, via the switch, is in series with the lamp and a thermistor is very high resistance when cold. Once the lamp is lighted, the switch is thrown to the other position and the lamp assumes full brightness. My Eumig projector, presently not in operating condition, instructions seem to indicate that some sort of lamp pre-warming system is standard on the Eumig.

On a somewhat related matter, lamp substitution charts are available at http://lms.jefferson.k12.ky.us/lamp.html. They have a second page of listing that I could access only by another Google search. Some of these lamps are used in motion picture projectors.

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Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003


 - posted November 28, 2009 08:47 AM      Profile for Paul Adsett     Send New Private Message       Edit/Delete Post 
Michael,
You are absolutely correct, pre-heating of the lamp filament is essential to get good lamp life. On the Eumig and Elmo projectors the lamp gets about 3 volts applied as soon as you switch the projector on (or in the case of the Eumig 800 series, as soon as you plug it into the wall socket). This low voltage produces a dull red glow on the filament, which as you say, reduces the 'shock' to the filament when the full voltage is applied.
I am not familiar with your Sears projector, but $120.00 for a lamp is incredibly expensive. Most super 8mm lamps cost about $15.00 -$30.00.

--------------------
The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
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Panasonic PT-AE4000U digital pj

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Winbert Hutahaean
Film God

Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003


 - posted November 29, 2009 06:52 PM      Profile for Winbert Hutahaean   Email Winbert Hutahaean   Send New Private Message       Edit/Delete Post 
quote:
One online USA source has the price over $120.00 each
You are not kidding?? $120

The lifespan of DLS is between 10 - 15 hours.

So every 15 hours you are, basically, buying one Sankyo 700 or Eumig Standard 8mm machine....!!! [Eek!] .... [Big Grin]

If I may ask what make this Sears projector special for you. What I knew everything with Sears is just re- branded from other cheap projector.

Or perhaps you mistyped it $120 which should be $20??

I am referring to Ebay auction below, everything was offered between $22-25 with buy it now option.

http://shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=DLS+lamp+&_sacat= See-All-Categories

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Winbert

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David Kilderry
Jedi Master Film Handler

Posts: 963
From: Melbourne, Victoria, Australia
Registered: Feb 2006


 - posted November 29, 2009 09:19 PM      Profile for David Kilderry   Author's Homepage   Email David Kilderry   Send New Private Message       Edit/Delete Post 
Hi Michael, topbulb.com, where I buy most of my lamps, has the DLS for $35.99.

My standard 8 Bell and Howell uses the DEF (now DCA) which is similar. The only short life I had on this type of lamp was a few years ago when I sourced one locally.

Lamp pre-heating is an excellent feature found on many Super 8 projectors (Eumig, Sankyo etc).

David

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