8mm Forum: That awful Elmo Lamp Socket

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Posted by Paul Adsett (Member # 25) on October 02, 2012, 09:22 AM:

Getting dim pictures from your GS1200 or ST1200? Don't blame the bulb, blame that awful lamp socket design. You know, the one where the bulb slides sideways into the ceramic socket.
My light output was getting terrible on my GS, and I thought it was time to replace the bulb. On removing the bulb I found that one pin of the bulb had totally eroded, and the socket contact had disintegrated. The reason for this is inherent in the Elmo lamp socket design, which has a spring loaded flat contact pushing on the outside diameter of the circular lamp pin. So what you essentially have is a line contact, which of course has ZERO contact area! So you have a very high contact resistance, and the result is sparking at the contact interface which eventually eats up the pin of the bulb and the socket contact. Before that happens though you start getting a dimmer and dimmer picture, because the bulb is not getting the full 24 volts - there is a big drop in voltage across that lousy contact.
I have replaced my GS sockets several times, and the scenario is always the same - they eventually self destruct. Well, no more. I have replaced my GS lamp socket with a regular GX5.3 socket which contacts the lamp pins fully around the surface of the pin. Result - truly brilliant pictures again!

Posted by Adam Deierling (Member # 2307) on October 02, 2012, 10:12 AM:

Paul, Could this be done on a st1200HD? How hard is it? What do the parts cost?

Posted by Hugh Thompson Scott (Member # 2922) on October 02, 2012, 10:25 AM:

I wonder how many people are blaming the little glass filter on
this projector for light loss when it's actually the light socket.
I had this problem years ago Paul, and did the same as yourself
and put in a new connection,as the lamps were being ruined
long before their expiry date and junked because of the pin
being eroded.

Posted by Paul Adsett (Member # 25) on October 02, 2012, 12:35 PM:

That's exactly right Hugh. To put this problem in real terms, I found that the light output of my 200 watt GS1200 had dropped to a level comparable to my 100watt Eumig! That's how much these poor sockets can kill screen brightness!
The modification is very simple because you can still use the existing metal cradle that positions the lamp. All you have to do is cut the lamp wires as close as possible to the existing cermic socket, trim the wire ends, and attach a piece of terminal block. The terminal block makes it really easy to replace the socket again if you have to in the future. Remove the old cermic socket from the metal cradle by removing the two little nuts and bolts. Be careful not to spill nuts, washers, and springs into the innards of the projector. Now the new GX5.8 socket comes with flying leads. Trim the lead length to about 6 ins and insert into the terminal block and tighten all 4 screws. The socket will not quite fit through the rectangular hole at the back of the lamp cradle, so you simply file it out until it will slip through and you can push it fully onto the lamp pins (make sure you don't do this filing operation near the projector- remove the cradle first). There is plenty of room in the existing lamphouse to accomodate the little terminal block and the extra lead wire, but you do need to unscrew and remove that central plate from the black lamp house cover.
Job done!

[ June 05, 2017, 09:42 AM: Message edited by: Paul Adsett ]

Posted by Mal Brake (Member # 14) on October 02, 2012, 05:36 PM:

Hi Paul,
Totally agree with your post except isn't there a chance the plastic around the terminal block will melt from the heat given off by the lamp?

The reason I say this is because some years ago a friend and myself picked up an Eumig 938S for just £80. The only thing wrong was the previous owner had carried out the same modification. The plastic had melted leaving a waxy goo in the lamphouse and of course exposed terminals.

Posted by Paul Adsett (Member # 25) on October 02, 2012, 07:29 PM:

Hi Mal,
Good to hear from you.
The socket that I used is all ceramic construction, so no danger of melting there. I was concerned about the insulation around the wire pigtails, but I ran the lamp on full power for an hour, and there was no sign of the insulation melting up next to the ceramic block, so for the particular connector that I used it is a non-issue. Certainly a plastic connector would melt almost immediately.

Posted by Tom Photiou (Member # 130) on June 23, 2017, 03:21 PM:

Paul, Thank you for your PM the other day, looking at this here, (sorry if i sound stupid), How is the bulb actually held in place? is it just the ceramic connector holding it in?
There are so many of these ceramic holder available, these are just a couple i found but i want to ensure the quality is there so it doesn't either melt or fall apart,

http://www.ebay.co.uk/itm/Halogen-Light-Bulb-Lamp-Holder-GX5-3-Ceramic-Pack-2-/250881761335

http://www.theinternetelectricalstore.com/hldr-gx53-kanlux-ceramic-socket-lead-72109-4442-p.asp?gclid=CjwKEAjw-LLKBRCdhqmwtYmX93kSJAAORDM6hUtysp4-8jsqa7Ajhy1k5xbH0aI2XVVyqiIpnmmq2B oCNVrw_wcB

https://www.amazon.co.uk/Ceramic-Holder-Halogen-Socket-35-MR11-MR16-Base/dp/B003YGVBL4

Three totally different sources, all very cheap, all ceramic. Any thoughts [Wink]

?

Thanks in advance.

Posted by Steve Klare (Member # 12) on June 23, 2017, 03:39 PM:

I had an adventure with this.

I bought a cheapy and within a couple of months the socket pin holder burned up on one side and took the lamp pin with it.

I went to the guy I buy lamps from and asked his advice. He recommended something better, and not that much more expensive, which actually had safety agency markings on it.

-that one has been in there several years without any problems.

(Sometimes you get what you pay for!)

Posted by Tom Photiou (Member # 130) on June 23, 2017, 03:53 PM:

Steve, could you point me in the direction of what you bought as an example?

Posted by Paul Browning (Member # 2715) on June 23, 2017, 04:28 PM:

Tom, the ceramic base is not that important, what is though is the connections made at the pins, avoid the flat style connections as these arc, and erode the pins, the enclosed style connector is more suited, most disco type suppliers do these type, as many of the earlier lighting effects used 24v 250 watt projector lamps. Martin lighting used this lamp base, and many years later are still working fine. Certainly go for the silicone type cables, unfortunately I would suggest just soldering the cables to the pins, this would eliminate any "spark erosion" at the pins, but this style of stranded cable is almost impossible to solder.

Posted by Steve Klare (Member # 12) on June 25, 2017, 06:53 AM:

Hi Tom,

This is the one I bought:

EFR Socket

It's pretty rare among these that it actually specifies a maximum operating current. A big part of the problem here is that we are operating a fairly high power device on low voltage. That means a lot of Amps and this puts a beating on things like socket contacts.

These are rated for up to 12 Amps. 150W/15V=10 Amps, so we are in!

Mine have the threaded sockets, so they are the Mitronix ones. I don't think they are particularly better (or worse) than the Buhl ones: maybe that's the stock he had that week.

I'll say this much: I bought three of them anticipating problems, but it's been a couple of years now and I'm still operating on the first one.

[ June 25, 2017, 09:05 AM: Message edited by: Steve Klare ]

Posted by Tom Photiou (Member # 130) on June 25, 2017, 02:23 PM:

Thanks Steve, appreciated.

I found this on Amazon today,

https://www.amazon.com/dp/B01H5SUQ2Q/?tag=phpprogramme

i'm not buying this, i stumbled on it by luck during a search but this is the closest thing i have ever seen to the original Elmo holder assy, and i ts on Amazon [Eek!]

Posted by Janice Glesser (Member # 2758) on June 25, 2017, 07:27 PM:

Tom...That's a QLV-1 Lamp holder. I buy these to do lamp upgrades on several brands of projectors. That Amazon price is way too high. You can get these off Ebay for $9-$10. In some cases I have to remove the socket on the QLV-1 and use the plug-in type shown in Paul's modification.

Posted by Paul Adsett (Member # 25) on June 25, 2017, 08:10 PM:

quote:
How is the bulb actually held in place? is it just the ceramic connector holding it in?

The bulb is held in place exactly as normal, by the hinged part of the lamp holder which swings down and clamps the front edge of the bulb. The only modification to the original Elmo lamp holder is the removal of the original socket, and the filing out of the hole at the back of the metal lamp cradle.

Posted by Tom Photiou (Member # 130) on June 26, 2017, 01:01 AM:

Thanks Paul. I see what your saying there.

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