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Author
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Topic: NEC NC-800C lamp failure
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 12-23-2014 11:16 AM
I haven't posted here recently; in October I was made redundant from my job at the college, and have not yet been able to find any paid work. Aldi are opening a new supermarket wery close to me soon, and were holding a recruiting event yesterday. I went along, but so did far more people than they would have been looking for, so no luck there.
Anyway, being umemployed, I have been spending rather more time than normal at the cinema recently. On Saturday 13th there was a special event for a local charity who, amongst other things were screening several short films, mainly from laptop, but one from DVD. The organiser of the event was setting up the next film with the douser closed, but when it was ready he was unable to open the douser. When I looked the lamp was out, and the projector in a cooling cycle. Once re-started we were able to continue. For various reasons the programme was running late, so they decided to continue with other parts of the event elsewhere in the building, and return to the cinema at the end of the day to screen the last film. While the auditorium was empty I was looking at the projector when the lamp went out again. We were able to show the last film later.
The next film was a normal public screening on Thursday. After about twenty minutes the lamp went out; again, I was able to re-strike it after it had cooled, and the rest of the show, about an hour and a half, ran without problems.
This show finished at about 13:00, and the evening one wasn't due to start until 19:30. It was now obvious that something was wrong so we contacted AAM and one of their engineers made some suggestions, but said that he thought the lamp probably needed replacing.
Somebody else was projecting for the evening show, but I went back in before he arrived; one of the trailers had to be run from DVD which he had never done before, and I needed to tell him about the lamp problems, and the fact that a problem with the sound system had been fixed. I decided to then stay on during the show. We were getting close to the end of the show, and I was thinking that it looked like we would get away without problems, and we could get an engineer in before the next show, on the 29th.
About ten minutes before the end of the show the lamp exploded. We hadn't expected this, and the engineer that replied to our e-mails obviously hadn't either, or he would have told us not to use it. There was no sign of any external damage, the fans were still running, the small display panel on the side of the projector showed that it was in a cooling cycle, and 'Lamp unlit'
There was no sign of any smoke, flame or arcing so I decided that it was probably best to let it complete he cooling cycle before shutting it down. we then stayed with the projector for about half an hour in case anything else nasty happened. There was an unpleasant burning smell, but this cleared after a few minutes.
The engineer attended this morning, with a new lamp module. What he found when he removed the old one was remarkable. The largest pieces of debris inside the module were only a few mm across, and these seem to be pieces of reflector judging from the shape of them; these had all been retained within the lamp module by the woven wire mesh over the air ports. Neither electrode is where it should be; the anode is in the bottom of the module, partly buried in debris. I cannot see the cathode, probably also buried. Almost nothing remains of the quartz lamp envelope; it seems to have totally disintegrated into very small particles, about the size of fine sand, or table salt. Some of these had been blown out of the projector, others were inside the projector, but little remained inside the lamp module.
The glass cover over the light output port in the lamp module survived without damage, there wasn't a mark on it, so no debris was able to get out that way. We may not like the price of these lamp modules, but at least in this case it may have prevented other, much more expensive, damage.
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 12-23-2014 03:27 PM
Richard,
That is interesting. The lamp which failed is probably about 4.5 - 5 years old, but has not had a great deal of use. The cinema was closed for just a few weeks less than three years, and since before the digital was installed was not open on Sundays, and operated for shorter hours than most cinemas on other days. I keep a record of lamp hours used, and estimated remaining, after the last screening of each film. After the Saturday event these figures were 946 and 717; assuming of course that the figures reported by the projector were correct. The Thursday shows would have added about three hours to these. We've used almost exactly 300 hours since re-opening the cinema, mainly for two shows each Thursday, in March.
The cinema is owned by the Council, who after they closed it removed the projector and moved it to a much larger venue nearby with a screen width of probably 10-12 metres and a very long throw. Unsurprisingly, they found that it was unsuitable, and eventually returned it to the cinema, where it was re-installed.
When the projector was originally installed it was running at significantly less than 100% lamp power, but I cannot remember the figure. I do remember that it was putting out more light than the Kinotons for less power. When the projector was returned to the cinema, which would have been about five years after I had last previously seen it, it was running at 100%. Whether somebody had increased it to try to make it useable in the large venue, I don't know, but it didn't look excessively bright in the small cinema. Recently, I actually thought it looked somewhat dim, despite running at 100%. Possibly this could indicate excessive blackening of the lamp bulb, but there is not enough of it remaining to be able to confirm this, just the sand-like particles. When I'm next there I'd like to recover the electrodes from the old module to see what condition they're in.
The engineer has left the projector running at less than 50%, and it is certainly brighter than the old lamp was at 100%, so something was obviously wrong with the old lamp.
The douser was closed when the lamp shut down the first time on Saturday, but I cannot remember how it was the second time. It was certainly open when it happened during the Thursday morning show. We never had any problems striking the lamp.
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 12-29-2014 05:03 AM
Never mind 'so violently', I'd just like to know why it exploded at all, and it's still something of a mystery.
Luckily, no damage outside of the lamp module, but we obviously don't want it happening again. If it had been a manufacturing defect serious enough to cause the failure I think it would probably have happened before the 949 hours use which it survived. If it had been damaged when moved it would probably not have survived the 297 hours which it operated after it was returned. It certainly wasn't over hours, unless the hours reported by the projector were incorrect. I don't think it was passing excessive current, it wasn't getting very hot. The dim picture could have been explained by excesssive blackening of the bulb, but I have no way of knowing if that was the case.
New lamp now has two hours on it and there are no problems so far. First show will be at 14:30 today; I won't be projecting for that, I just came in this morning to make up some programmes for the next two weeks, and ingest another film for which there wasn't room before.
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