NEC 900 lamp light issue

[Michael Drumbore]

I'm having trouble with our NEC 900C lighting the number 2 lamp in the machine. Initially we were told it was probably a bad ballast and had that replaced and this corrected the issue for a time, then the issue returned. I've swapped the lamps and they all strike fine in the number one lamp slot however any lamp that's in the number 2 slot will not light. We've been running with just the one lamp since the projector is mainly used for for preshow slides and that is bright enough for that purpose. However if we use it to run the occasional digital feature it's fairly dim without both lamps. Any help or insight on how to trouble shoot what the issue is and repair it? Currently the error code that's coming up is "Lighting start failed or lamp off".

[Leo Enticknap]

Assuming that the ballast has definitely been ruled out as a possibility, the only other thing that occurs to me is something in the training slides for the NC900: "A lamp sync signal is fed from the ICP PWB via the mother PWB to the lamp ballasts. Due to being AC lamps they have to be synced to the video frames. The ICP and mother PWB [printed wire board - NEC's term for a printed circuit board] cannot be used from another Series 2 projector as the lamp sync line will not be included. ICP = 7N951811 / motherboard = 81X15M01."

Therefore, I'm wondering if this sync pulse could be involved in the issue, and that if pulling, contact cleaning, and reseating the ICP might help. Maybe if the ballast doesn't receive the sync signal accurately, it borks out and throws a "lamp unlit" ?

Incidentally, if the ICP in an NC900 goes out, you potentially have a significant problem, because it's a modded one; not the stock TI board. The last time I had this happen (in May), there was a three month back order for a new one.

[Michael Drumbore]

Thanks Leo, I just pulled cleaned and reseated all the boards from the side of the unit and no luck.

I will add there is a soft clicking sound while the unit powers on that only happens when the lamp is not going to strike.

is there any way to test a ballast to see how it may have gone bad and correct the issue. Or could it be a matter of reseating the connections to the ballast?

[Leo Enticknap]

Hmm ... the soft clicking sound seems to me like an igniter/start pulse generator. Mercury vapor lamps are arc lamps, and so something has to strike them; but I don't recall any reference to a separate ignition circuit in the service training material (which I'm sorry, but I can't post snips from here, because the slides are marked confidential/do not distribute). Maybe the ballast card handles this as well as the actual ballast function (limiting the total current/amperage that the lamps can suck)? If the igniter were on the lamp assembly itself and malfunctioning, then when you moved lamps between the slots, the fault should move with them, but this is not happening, so we can rule that out.

I find it hard to believe that a second ballast card fried so soon after the first, unless something external is happening to fry them. But both are being fed from the same power supply, so you'd expect whatever is taking out one ballast to take the other as well. Maybe worth opening a support ticket with SharpNEC, in case they've seen this before and know immediately what is going on?

[Michael Drumbore]

That's really what I'm starting to think if there is something else in the projector that is causing just the number 2 ballast to have an issue. I have an email in with SharpNEC cinema projector division now, as well as an NEC tech I had spoken with before on the issue.

Thankfully our theatre mainly runs 35mm so this hasn't been a pressing matter or causing downtime. But we do have some digital programs coming up and I'd like to finally get this issue to bed once and for all and have the presentation as bright as possible.

[Gordon McLeod]

The ignitor is part of the ballast
Try swapping the ballasts to determin if you lost a second ballast
also check the wireharness and connectors I had one with a burnt connector

[Michael Drumbore]

I can give that a try. Would you recommend just swapping the wire harness leading to the lamp with them in place to see how it behaves to start without disassembling entirely?

[Leo Enticknap]

If you just swap the wire harnesses around and the problem moves, you know that either a ballast or a wire harness is bad, but it could be either.

Suggest disconnecting the harness from ballast 2 entirely, and then connecting 1's harness to 2's ballast. You'll get a "lamp unlit" on what the projector now thinks is 1 (2 in reality), but ignore that. If 1 in reality (what the projector now believes is 2) lights successfully when connected to 2's ballast but with 1's harness, that would point the finger at 2's harness. But if you get "lamp unlit" on both of them, it would look like 2's ballast has failed.

Given that replacing ballast 2 fixed the problem temporarily, I think Gordon could be on to something (a poor connection adding resistance that the ballast card cannot cope with).

[Michael Drumbore]

Thanks, I'll check this all out tonight when I get to the theatre should be able to try this before we open for our show tonight.