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Discussion Starter #1
I have recently bought a GE901 projector (NEC PG9) in perfect shape with 900 hours only. This machine was probably unused for years. I turned it on a few times for some hours with no problem. Then a few days ago I left it on five hours projecting a (very good) image again with no problem (at ANY brightness and contrast position). Three hours later turned on and it went off in a few seconds. Turned on again it worked (perfect image) twenty seconds then off... Now it always stays on one second then off for five seconds and loops this way infinitely. No codes on back display.

I have service manual so I tested power supply outside projector as they say. Putted a 3.6 Kohm 10W resistor on the 180V output to avoid protection cut off and applied 1.5V DC on the specified connector and I discovered power supply itself to have the same behaviour of the proj!

On for a second only. Interesting think is that I get ALL correct voltages while PS is on (used a peak hold function tester). Is this PS behaviour in stand alone mode correct?

When proj is on two red leds on DEF board are on, but I’m not sure this is a real problem because PG9 goes immediately off. Anyway I checked Horizontal output transitor on DEF board and it’s not shorted. Thank you.
 

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Fvale,

Pull the HV red leads that go to the splitter at the splitter, lift up on the boot not the red leads, it will break the connector, not the flyback but the tubes, try to power it on, keep everything away from the splitter as well as your hands. If it still shuts down lift the CP connector on the c-drive located under the deflection board between the tubes, if that doesnt work plug that back in and lift the FP connector at the f-drive, if that doesnt work plug that back in. Disconnect the rgb connectors and connect a video source, if that doesnt work, let us know. Doug
 

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Discussion Starter #3
I pulled the three HV red leads out of the splitter and IT POWERED ON! GREAT, I'm really happy!

I didn't think about HV problems because I could hear it's particular sound and power supply itself didn't seem to work.

I also tried to connect one tube only (blu) HV red lead to splitter and projector remained on with tube projecting full blu screen at high intensity and then cutting it off with projector always turned on.

So I think I'll need to replace the splitter...

Thank you very much Doug! Fabio
 

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P.S. I don't understand why NEC want people to became mad for nothing. I mean I carefully read service manual about power supply testing. I made all requested operations but power supply goes off in seconds while I discovered it to work well. I don't know or I could miss some information about swithing PS. Fabio
 

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fvale,

Im not so sure, try storing a low contrast setting before it shuts off, see if it stays running. There are a few things to still consider, the HV protect circuits could be doing this also but that usually shuts the projector down to standby.


Because the projector sat for so long it just might need to run a bit, if you can store the low contrast setting and keep it running it might clear up.


Try just one tube then another until all 3 run, the NEC doesnt usually loose the splitter.


Most mfgs try to keep you away from the HV, its not the safest way to troubleshoot. Doug
 

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Storing a lower contrast settings was impossibile. I have a old NEC GP3000 that uses same splitter and HT filter (with different cable runs only) so I changed them. First splitter but no improvement, then filter (I think it’s a HT filter) and again nothing. In this condition with all 3 tubes connected to HT I got high bright full screen on each tube followed by a cut off while projector remained turned on. Then I installed back original splitter and filter and problem were the same. Note that last time I tried this it was not possible to turn projector on with all 3 tubes connected.

After detaching and connecting HT red cables on splitter, projector turned on without projecting full screen white image. It was working. Same day I used it two hours and it didn’t turned off. Later another two hours and I had to turn it off.

I hoped it cleared up but at night, same day, It remaned on 20 minutes only and then off itself showing a “FA†error code blinking on display, my service manual doesn’t have that code. Now it turns on one second and then goes off in stby for four seconds looping infinitely this way... Sometimes it remains on more time projecting a good image then off, not in stby, but with remote and power leds on. Very strange, I’m afraid it’ll be very difficult to find out where this problem is. Note that when it works it’s absolutely perfect and turning off is not related to brightness and contrant controls at all, they can also be at maximum with no cut off. Thank you.
 

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Fvale,

There is a AF error code that relates to the power supply. You might try to reseat the boards taking a good look at the video out power board, reseat that also. On the deflection board locate H OUT pot and mark this, dont turn it but just rock it just a tad to see if it helps, dont get this out, just try to clean the VR. From here you will need to start at the connectors of the power supply and check all the voltages and see where to start, also check the deflection voltages. Keep an eye on the error codes to see if it changes to a dual error code, if it does this will point you in the right direction.

Try lifting the FP connector on the f-drive, then try the CP connector on the c-drive. Normal operation the standby will be off when running. Good luck. Doug
 

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Discussion Starter #8
Error code was FA not AF for sure. I’ve reseated video out power board as all the others and rocked H OUT pot but nothing. So I again checked all voltages on power supply, unconnected from projector, and all were present. Just to have another try I disconnected all tubes HT cables on splitter and this time projector went off in one seconds as they were connected. Problem is not on the HT now I think it’s power supply, but I need to know one think for sure.

My PS with 3.6K resistor on the 180V out and 1.5 DC applied on connector 1A 4 (+B. CTL) as stated in service manual goes off in one second... as projector does when PS is connected. I think, if PS is ok, it should remain on under this conditions. Can someone confirm me this please?

Now I remember that a few days ago doing same test PS unconnected remained on more time, probably if it were in projector it would have worked for a few hours!

Next days, if I’ll have this information, I’ll change all few IC’s in PS, only Sharp photocouplers PC111 seem hard to find here in Italy. Thank you.
 

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Discussion Starter #9
After having worked many hours, changed all IC's, I discovered a little bad diode in the PS. Now projector is working fine.


Thank you Doug.
 

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Congratulations! You're a better man than I am. What diode was it?


Marc
 

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Congratulations !! That great that you discovered the problem ! The description you gave seemed similar to some other problems posted here, surely your solution will help many other people who love this forum. Post some screen shots from your newly fixed pj when you get the chance.
 
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