Sunday this week was a council-mandated clean-up day. It’s a time for much illegal dumping and moving of old furniture and CRT TVs to the side of the road. It’s also a time for salvage people (myself included) to pick up some interesting, valuable items discarded by others. Unfortunately, the fun is ruined by more “serious” salvagers who drive around with box-vans, utes with cages and trailers picking up anything with metal just to get scrap metal value for it.
Anyhow, this time around, I was totally out of action, due to the state of my ankle. I sat out this salvage. However, I still had this item from a prior salvage which I had always intended to post on my blog at some stage and disassemble.
It’s a complete lamp assembly, which is probably beyond its useful life. It’s definitely some high powered type of lamp – not your average old halogen, and it has a very nice shiny reflective parabolic shape. I’ve always been interested in strange light globes since I was small – so this is “just another field day” for me. I suppose anyone who has one of these TVs or a modern projector would be intimately familiar with this type of lamp, which was formerly so expensive that one wouldn’t afford to replace the lamp in their projector, instead opting to replace the projector itself. Now, the prices are somewhat more reasonable.
Turning it to its side reveals its identity. Marked BP96-00826A(P), it’s a Philips UHP lamp for a Samsung DLP rear projection TV. UHP lamps are known by the name of ultra high performance and of ultra high pressure, and are a type of mercury-vapour lamp. The main reason I’ve taken a while to get around to it is because of the nasty things I’ve heard about these lamps “when they go”. Explosions, shattered glass and loud bangs are common – you really need to be careful as high pressures can move glass shards quite quickly, embedding themselves in your face if you’re really clumsy.
Of course, with some trepidation, I continued examining the lamp. It looked okay from the front, so as long as I’m careful, it should be fine.
On the other side of the assembly, there is a power connector, which appears to have been made for easy module disconnection. It’s screwed into the frame, and the cables are sheathed in a rubberized silicone heat-shrink like material, probably to let them survive the heat.
The rear of the module is covered with a metal shell, which probably ensures the lamp holds its shape and protects the inside of the TV against hot shards. It’s marked BP6H00731A #1 AL BRKET-LAMP,COVER 23. At the top, in the hole, we can see a scoop-like shape, and it is lined with a fine layering of dust inside. It seems forced air cooling was used with this lamp and air would be funneled from one side of the lamp, into the lamp, and out of the other.
A close-up of the scoop reveals that it channels air into an open part of the lamp. Also visible is the rear, less shiny glass body of the lamp, and its retention by several screws and frames.
The screws holding the rear aluminium shell have been removed, showing the rear of the lamp. For those “adventurous and willing”, a cheaper option to purchasing a lamp assembly is just to purchase the lamp itself and remove the existing globe and bolt/screw the leads to the new globe. Here, we can see the connection mechanism – one terminal is secured by a bolt, the other by a screw to the side of the lamp. The lamp itself is retained by a black frame secured by four screws.
After removing the outside screws and the inside bolt and screw, this is the connection wire itself – nothing fancy. All the required electronics – i.e. the starter and ballast, are contained within the projector or TV, meaning if you have trouble with your lamps consistently you may need to replace the whole projector or TV!
After the black frame and lamp is removed, this leaves a cast metal frame of some sort, likely to support the front of the lamp and shield the plastic somewhat from the heat. It may also serve to reflect some of the edge-light back into the beam, I’m not sure.
Now, the good part – the lamp itself.
A direct frontal view of the UHP lamp reveals the capsule which sits directly in the middle, with its long axis perpendicular to the image here. One electrode escapes from the rear of the lamp as established earlier, and the other escapes through a hole in the side, where solid wire is joined to the lead-wire from the capsule. It probably also serves as a mechanical support.
The front of the lamp is actually protected by a cover glass which is quite thick and adhered to the rear of the lamp (the grey adhesive is visible in the corners), thus making it less likely an explosion would damage any of the “following” optical components.
The lamp markings indicate the use of mercury in the lamp. The lamp was Made in China by Philips.
The rear side of the lamp shows how the tab and wire electrode are attached to the glass reflector. This type of attachment looks vulnerable, so extreme care must be exercised not to over-tighten or put too much force onto it, otherwise it could snap and destroy the lamp entirely.
From the side, you can see the cooling vent as designed – there’s a matching vent on the other side of the lamp. This means the air flows right to left or left to right when the lamp is oriented with the print towards the UP facing side. The lamp itself probably requires very clean air for cooling, to avoid deposits on the envelope which may shorten lamp life and potentially cause cracks.
The vents can be easily seen by looking at the lamp at an oblique angle.
The most interesting part to me was the envelope of the lamp itself. It appears to be a very thick or double envelope of some sort. Inside the envelope appears to be a flat grey dielectric sheet for the discharge to run along, which may be containing mercury (I’m not sure).
From a different angle, the sheet is much more clearly seen. Also interesting is that the outside of the envelope seems to be marked with some coding, possibly for identification purposes, that says 4686N5c40u.
Another shot from the side and you can just barely make out the end of the code, and it’s now fairly clear that the inside of the envelope has a sheet-like material inside.
Having never handled any UHP lamps before, I can definitely say, it’s not so hard. I suppose if I were to replace one myself, I could do it – but with care, of course. I’ve never seen one up-close and in person – and now I have without having to pay a cent. It’s interesting just what people can end up throwing out onto the pavement outside …