2-pin HPL750 lamp

[LPdan]

I was replacing a burnt out HPL750 lamp in our theatre, and noticed it only has 2 pins like a 575W lamp. It is an Osram, made in Mexico. I was under the impression that 750W lamps always have the 3rd pin so they cannot be inserted into a socket not rated above 575W.
Any ideas about this? I can post a picture if needed.

 

[dreamist]

I was replacing a burnt out HPL750 lamp in our theatre, and noticed it only has 2 pins like a 575W lamp. It is an Osram, made in Mexico. I was under the impression that 750W lamps always have the 3rd pin so they cannot be inserted into a socket not rated above 575W.
Any ideas about this? I can post a picture if needed.

Sure it wasn't clipped off? I've seen the third pin clipped off before, when someone was really in a bind...

 

[ship]

Pulled out is more likely. At the time people didn't realize that the gauge of wiring was the main reason for that roll pin preventer.
So they just pulled them out so as to fit in the un-upgraded lamp socket. I can remember upgrading the wiring but also having to drill the lamp socket for the roll pin as a more difficult but proper way to do it initially.

 

[DELO72]

"Pulled out is more likely". Yes, if the third pin is not there on 750W HPL lamps, then whoever bought the lamps removed the pin.

 

[jhochb]

Good Morning

After the first couple of years ETC realized the old casting could handle the extra heat of the 750.
It could be they no longer need the pin

 

[LPdan]

Here are photos of the top and bottom of the lamp. There is some discoloration in one corner, but I doubt if someone pulled out the pin they would fill it in. I'm just curious about this.

 

[derekleffew]

The pin could have fit into the outer most groove on either the top right^1 or top left^2. in your first photo. Notice the top grooves are more rounded than the bottom ones.

An HPL750 lamp base, 115 or 120v.
^1 Pin is top right (If looking at the base from the bottom with the pin on top.)

An HPL550 lamp base, 77v for dimmer doubler applications.
^2 Pin is top left (If looking at the base from the bottom with the pin on top.)

In either case, the pin could have been removed leaving virtually no trace. Pulls right out with any pliers/Leatherman/Gerber.

 

[LPdan]

You nailed it. In my head the pin came out of the bottom, but once I actually looked at 750 W lamps, I see the pin is simply pressed into the fin slot. Makes much more sense now!

 

[Jay Ashworth]

I, too, thought that it was an actual "three-pin connector", like a mini-Bates.

 

[KLM]

I remember being told to pull these third pins back when I had just started working on lighting at my high school... makes me cringe today!

 

[DELO72]

Good Morning

After the first couple of years ETC realized the old casting could handle the extra heat of the 750.
It could be they no longer need the pin

NOT TRUE AT ALL.

The "casting" was never the issue. The original Source Fours had lamp holders and wires that were not rated for 750W (and the corresponding current & heat.) ETC switched to an improved socket with an improved wire (higher temp insulation, thicker gauge wire) in conjunction with the design and release of the 750W HPLs.