Could someone send me a link to this service bulletin, and describe the location of R556? I have a FE950 apart and am looking for it. But I can't locate R556 on either the schematic or the OSC PCB.
This monitor recently got the "vertical line" problem after a few weeks of spontaneously powering off and then back on. So I hope that R556 blown is the only problem -- but not optimistic.
Thanks,
Doyle Nickless
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to Wayne for bulletin. Nice people here! I repaired one FE950 and one FE950 still waiting for repair :) I also have one monitor of the same type jittering, but I don't know how to fix it.
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I belong to a couple of repair groups and repair more monitors than anything else. I have three NEC 950's sitting here. They usually play, but at almost any time the screen "colapses" and I get nothing for a few seconds and then they come back on. I see that you know of a "fix" for these machines. I would appreciate it if you could help me by sending information.
I live in Appleton WI and have been repairing electronic equipment for over 40 years. Monitor repair is slowing down, but I still repair a few every week.
Richard
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power supply and high voltage climb up and then they go down and up again.the amber light turns green momentarily and back to amber.sometimes the monitor comes on and works fine.then the width comes in on sides and then lost of sync and shuts off.then we start over again...
Can you help please.
thank you,
Danny...
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power supply and high voltage climb up and then they go down and up again.the amber light turns green momentarily and back to amber.sometimes the monitor comes on and works fine.then the width comes in on sides and then lost of sync and shuts off.then we start over again...
Can you help please.
thank you,
Danny...
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Hi! I'm sure you're sick of emailing this bulletin, but I was wondering if you could send it my way. I just found an NEC FE950 in the dumpster with the aforementioned problem. Thanks!!
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If someone still has got one of these monitors jittering, i may have found the solution... I fixed my own by replacing 2 dried electrolytic caps (their esr was too high) near IC591. They were C594 and C593, both 33uF, 25V.
Juhani
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same here, c594/593 and C591 on my FE1250 fixed the jittering. Oddly, the schematic calls for 33uf/25v High Temp caps in these positions, mine came from the factory with one 47uf 105°C another was 47uf 85°C! This last cap measured about 50% rated capacitance.
if you're in there (have to remove the OSC board to replace those caps) you should also consider the IC591 / R556 update at the same time.
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I just require some clarification here and maybe the rest of my post is not required. First I nabbed that service bulletin and schematic already.
I have the FE950 and the original post here refers to a vertical line. Is that correct or am I just missinterpreting the lingo and my problem is unrelated? Monitors are not a strength of mine as you may notice.
I am losing vertical deflection so I have a single horizontal line accross my screen. The problem appears as an intermittant issue and I can literally whack it back (sometimes). So I assume it is a mechanical issue. (I'm using the monitor as I write this).
Ok, if it's not the same, then I move on.
I will be fixed if I can find the faulty component joint if that is what the problem is. I have resoldered the deflection coil connections and associated parts in that area. Played with the connector wiring to that top crt board. Moved down to the HV section and resoldered various joints that even looked damp let alone cold.
About the only thing left is that osc board mentioned in this thread and of course it is located up front on the topside. Am I still on the right track here and it is worthwhile taking the next disassembly step? Or should I redouble my efforts esle where on the mainboard first?
Any experience similar or higher knowledge and assistance would be greatly appreciated.
Terry
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Hi if you still have access to a scope check V-saw on the output of IC512, you may be able to see a difference in voltage even with a meter.
If this always remains the same when fault present or not then this rules out IC501 you can then move on to the output circuit.
V-saw passes through 4 op-amps and emerges at IC422 pin7 check level whilts fault present and not.
Last is IC401 LA7841 these certainly suffer from dry/brocken solder joints depending on how rigid the tab is to its heatsink.
If you have a scope then check the output on pin 2 of IC401 if you have a square wave while the fault is present then useually the fault is and o/c output component i.e. scan coil/connector or R406 or any series component/link from IC401 pin 2 through the scan coil connector pin 1 then the scan coils then through the scan coil connector pin 3 lastly through R406 to GND.
Check the supplies to IC401 -15V pin 1 and +15V pin 5.
Rich B
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Thank you very much Richard. More than I had hoped for in advice.
I'll dust off my old 10meg scope and see if it still works and how far out of cal. it is. LOL
I reviewed the schematics. I see where you are coming from.
Thanks again Richard.
Terry
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Cheers for all the infos above.. i had exactyly the same issue as the guy above, and after an evening with the scope and checking out the input and outputs from ic401 i found the problem was dry joints on the scan coil connector. so all fixed and working fine now!
Thanks again for all the infos above
Richard
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