NEC FS5197 TV, Blank screen, sound okay

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Any one help on an NEC FS5197. Has a blank screen, EHT and heaters okay,
sound is okay. I replaced Q681 which was faulty but that didn't fix the
fault. Circuit around Q681 appears okay.
(Unfortunately I don't have a schematic.)

Thanks for any help in advance
TJB

Re: NEC FS5197 TV, Blank screen, sound okay



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If EHT and heaters are ok, the problem must be manifesting on cathodes
or grids. (Emission so dire you cant see a thing is pretty unlikely,
but I have come across it once.) I dont see that theres anything to
suggest other than metering those and working back from them. Of course
the cause may be far away from the cathodes, possibly as far away as in
the tuner. Without a cct diag youre going to have a hard life!


NT


Re: NEC FS5197 TV, Blank screen, sound okay


And what is Q681 "bingo"?

is it the HOT or what"

TJB wrote:

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If EHT and heaters are ok, the problem must be manifesting on cathodes
or grids. (Emission so dire you cant see a thing is pretty unlikely,
but I have come across it once.) I dont see that theres anything to
suggest other than metering those and working back from them. Of course
the cause may be far away from the cathodes, possibly as far away as in
the tuner. Without a cct diag youre going to have a hard life!


NT



Re: NEC FS5197 TV, Blank screen, sound okay



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Thanks guys but ----- A big sorry --
I forgot to mention that the on screen display is working fine. The crt and
it's voltages are okay. The problem is in one of those multi-legged devices
or in a switching transistor(s). Video In or TV just produces a blank
screen. Setting the onscreen menu to display a blue background for no
signal also produces a blank screen. I started poking around the
transistors located around the tuner/video stage. Unfortunately as I said I
don't have a circuit so it's a bit tough to find out where each stage is
and what each section does.


TJB


Re: NEC FS5197 TV, Blank screen, sound okay


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So how do you expect to check the voltages and waveforms at all the key
points if youve got no cct diag? How are you going to narrow the fault
down until you find it with no such info?


NT


Re: NEC FS5197 TV, Blank screen, sound okay


snipped-for-privacy@care2.com wrote in

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By asking in these newsgroups in the hope someone may have helpful info.
Failing that get the data sheets of the various chips and work around
them. Fixed a number of sets with no ccts, some problems are very simple
to solve, others just time comsuming.

TJB

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