NEC 900C recurring issue

[Armand Daiguillon]

Hello all,

I've posted about this issue before and you guys gave some great feedback - which I tried, but so far nothing has worked.
Here's a recap of the issue - if anybody can think of anything else to fix this let me know please !!

I have an NEC 900C projector, my certified tech so far has not been able to resolve the issue.

The projector in queustion keeps losing its marriage and the following errors show in the DCC log.

When it first stops working, the main error window in the DCC shows “no errors”, but if you look at the ICP status directly it shows the following errors -

General Status:
Security Event
ICP Communications Status Error

System Error:
OK

Security Status:
Security Enclosure Armed
Physical Marriage Tamper
Marriage NOT Active

Then after a few minutes it shows in the main DCC error log as -

2023/03/26 06:48:25(U)(584) IMB:Marriage NOT Active
2023/03/26 06:48:25(U)(582) IMB:Physical Marriage Tamper
2023/03/26 06:48:25(U)(520) IMB:ICP Communications Status

If I tell it to re-marry it fixes the problem, but then in between 5 minutes to an hour it stops playing and the same errors are shown again.

It always starts with the "ICP Communication Status" error (which is the only error that shows on the projector itself) and then the rest follow.

My tech said it could be any number of boards so we have been methodically swapping out board by board with another projector that is working.
So far we have not found the problem.

First we swapped the ICP board, then we swapped the “CPU” board, then we swapped the “Slave” board. Then we ordered a new “main board” directly from NEC, thinking that had to be it, since all the other boards plug into that one.
That arrived from NEC yesterday and was installed today – but the same problem keeps happening.
In my last post about this we were getting other tamper errors mixed in, but those have since gone away after the board swaps, now its just the same thing over and over.


Does anybody have any idea what is causing these constant errors ? Its my understanding that all the relevant boards have been swapped, yet we have no resolution.

Any insight would be appreciated !!!


Thanks !

[Mark Gulbrandsen]

Other than checking the sensor switches on the card cage and possibly treating the edge connectors with De-Oxit... Nothing really comes to mind except internal wiring, or the power supply..

[Steve Guttag]

The switches are the most likely culprits. Note, too, I've found where IMB face plates don't always engage well with the tamper switch for their slot and have had to pad it out with a bit of foam.

[Armand Daiguillon]

Interesting, how do the sensor switches cause an ICP com error ? If a switch is bad does it cut off the communications somehow ?

[Steve Guttag]

Honestly, it probably doesn't...they will cause the remarry requirement. A communication should not cause a remarry. If board swaps don't seem to affect the ICP comm error, then it would point towards its signal backplane (that which conveys communication between the various boards. However, you've now changed that.

I'm curious, when it has an ICP comm error, have you tried talking with the ICP directly (TI's ICP/Enigma program)? What is the status via that program?

Note, sometimes the logs will be deceptive in that there may not be a clear cause/effect. Again, a mere communication error with the ICP should not cause a marriage tamper. it should require a physical tamper. Think of it this way, updating the ICP, which would cause a communications issue, should not cause a tamper. Additionally, if an ICP comes up in a bad state, that shouldn't be a marriage tamper when a reboot could "fix" it. Now, if the ICP is removed, then you'll get a marriage tamper as not only will a microswitch trip, the ICP will know it is no longer plugged in and will signal a physical tamper to the IMB (the security manager...which is the entity that will call for a remarriage). So, it can be your IMB/IMS that is erroneously declaring a tamper.

Have you changed the IMB/IMS (or done a swap to see if the problem moves)? I, also, wouldn't rule out the microswitches SW PWB ASSY (NC)
79TY1351. I don't know how it will respond if one pole is not making contact without the other pole making contact.

[Mark Gulbrandsen]

The switches are the most likely culprits. Note, too, I've found where IMB face plates don't always engage well with the tamper switch for their slot and have had to pad it out with a bit of foam.

I believe that GDC put a short round thingy on the back of the faceplate that protrudes in towards the switch slightly to make sure the switch gets fully depressed. If the switch appears to be fully pressed in, he could always take a short alligator clip lead and short out the switches one at a time to see if that solves the problem. I actually never had this sort of issue with the 900's, but the very early units shipped, all had shorts develop in the vertical lens mount positioning motor. That also blew out the lens motor driver card. The actual fix took less than 10 min. But you had to remove quite a few other things before you could remove the lens mount. I think the last one I got it down to 4.5 hours.

[Armand Daiguillon]

The tech guy said he bypassed all the marriage related tamper switches, but i'll try swapping the imb and deoxing all the cage switches anyway - maybe i'll get lucky.
I have two projectors down now. Ugh !

[Armand Daiguillon]

So, I swapped IMB, worked for two hours ... now same errors are back.
My tech guy says next steps are to swap the "internal router" and then the IMB's server unit.
Does that seem like a good course of action ?
Personally I'd like to just hit it with a hammer. But thats probably not as productive

[Mark Gulbrandsen]

Power supplies would be next. They can also be swapped....

[Brian Vita]

Although its an absolute pain in the a** to replace, my money would be on the backplane. Changing one on an NC900 is no picnic but it addresses all of the issues that you mention.

[Armand Daiguillon]

Although its an absolute pain in the a** to replace, my money would be on the backplane. Changing one on an NC900 is no picnic but it addresses all of the issues that you mention.

We changed that out a while ago .... we changed everything that can be changed out. Nothing helped until NEC tech support suggested swapping the "internal router" - that itself did not work, but then we changed out the ethernet cables that attach to the rear of the back plane ... and that seems to have done the trick.
At least we hope so, it has gone a few days without errors before. We're on day 2 of no errors so far ... we're hoping for the best !

[Fraser Falconer]

Hi Armand,
My money is on the switches.
Generally it is the switch on the Lens Cover, when I have had this issue. Even though it should trigger a service door Tamper it causes a Divorce (Marriage Tamper) and all the errors you have mentioned. Other than that it will be either of the switches on the Card Cage. As mentioned in an earlier post ensure the switch is fully engaged. I have had switches that read okay, but I have replaced them because of the time involved in strip down, and even though it reads okay the internal resistance or tarnish is enough to cause the problem. As mentioned in other threads, the low current and voltages in these circuits can cause issues.

Cheers Fraser

[Leo Enticknap]

Agreed with all on the time and complexity of the stripdown for a 900 or 1000 (or any other of the smaller NECs, for that matter). For this reason, if ever I have to strip a card cage, or around it, for any reason, I would always recommend to the customer that the motherboard/backplane and both card cage tamper switches be swapped out. They are not pricey parts, and they will die eventually. If an end user is going to invest in 3-4 hours of tech labor, it makes sense to replace all the relatively cheap parts that are a known significant failure risk after a few years (the motherboard and tamper switches definitely qualify) and which are not that expensive.

[Brian Vita]

We changed that out a while ago .... we changed everything that can be changed out. Nothing helped until NEC tech support suggested swapping the "internal router" - that itself did not work, but then we changed out the ethernet cables that attach to the rear of the back plane ... and that seems to have done the trick.
At least we hope so, it has gone a few days without errors before. We're on day 2 of no errors so far ... we're hoping for the best !

That actually makes perfect sense. The boards plug into the backplane to RJ connectors on the back of it. The RJs connect via the cables that you mentioned to the router and from there back to the backplane or to the outside world. I wouldn't have thought the router because you were still able to connect to the projector. When I've had routers fail, I couldn't talk to the projector. Good catch. I wish you the best. BTW, it is critical that the router outputs go the exact ports that they connect to. Each port of the router is programmed to speak to a certain slot on the backplane.

Best of luck!

[Leo Enticknap]

I was once told by NEC tech support that the cable to the external jack needs to go into the same jack on the router (spaced slightly apart from the other four, IIRC), but that it doesn't matter where the other four go. In practice, if you're replacing the router but not the cables, the existing cables will have settled into a shape that lines up with the jacks, meaning that you'll likely plug them back into the same places anyways. Obviously that doesn't apply if you're replacing the cables.

However, that advice was given to me in respect of a 3240, not a 900. Maybe the four internal device connection cables are jack-specific on the 900?

A router failure will break Ethernet communication, but not RS232. I once serviced a 900 that must have had a faulty router for a while, because it was operated by RS232 automation and no-one noticed. The reason I was called was that the lens shift motor bit the dust, but when I arrived, I saw that the projector (in a pod, so the side panel display was not visible to anyone) was also reporting a router error, and I could not connect to it by Ethernet.

Thankfully, the router card is not very expensive (by NEC parts standards) and pretty easy to swap out. It's in competition with the tamper switches for the part in a 900 that is most likely to fail, in my experience.