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 My NEC TV lacks brightness.
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 Return to top of page · Post #: 1 · Written at 7:52:31 PM on 28 February 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 880

I guess this TV qualifies as "vintage"!

We bought our NEC in 2001 and of late we really have to turn the room lights down to see whats happening in the dark part of scenes!
It is a CRT device. I have never had the back off it so have no idea what is inside but I bet there are no valves.
The set remote does have a "picture mode" setting and that gives 3 definite levels of brightness/focus called Soft, Standard and Bright.
The only viable setting is Bright. The colour balance is very good to my eyes with rich colours, a good range of hues, clean and pin sharp focus.
I have tried all sorts of other settings on the remote that affect the picture but the basic fact is the picture lacks brightness, its too Black.

The back sticker says its a NEC model FS68V80.
What do I stick a screwdriver into to brighten the tube up?
The TV is fed by an external Jaycar set top box which drives AV2 input so the front end of the NEC is out of the equation..
I must note that while the free to air channels were still on air via the Tuner of the NEC, the set top box always produced a superior picture.
Any hints or suggestions welcome.

Cheers, Fred.


 
 Return to top of page · Post #: 2 · Written at 8:35:00 PM on 28 February 2020.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 409

Fred, the fact that the picture is in proper focus etc. suggests to me that the G2 needs turning up a fraction.
Probably due to a component aging in the screen voltage section.
Need a close look at the circuit first.
JJ


 
 Return to top of page · Post #: 3 · Written at 9:48:07 AM on 29 February 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1904

The G2 is one of two "knobs" on a raised section on the back of the HV block. That's the black semi-cylindrical thingy with the red high voltage lead coming out the top.

The upper knob is the focus, the lower one is G2. Turn it up just a fraction, no more than you need to light the screen on the blacks. Too far and you risk getting retrace lines and upsetting the colour balance.

You might check the focus while you are at it. Aim for best focus in a circle equal to the height of the screen. It won't be perfect over the entire screen.


 
 Return to top of page · Post #: 4 · Written at 12:26:00 PM on 29 February 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 880

Thanks guys I'll pull the back off fight past the cobwebs and have a twiddle!
Fred.


 
 Return to top of page · Post #: 5 · Written at 11:23:35 PM on 29 February 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

Fred,
I have a few 90s NEC CRTs and they ALL developed the same problem of the screen going a bit dark and then it will go green in time.
Still has a image but it goes green.
I have spoken to a couple of people that feel it's a bad batch of 90 caps
China made ones perhaps?
Pete


 
 Return to top of page · Post #: 6 · Written at 8:43:52 AM on 1 March 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1904

No you can't blame the capacitor plague for this one.

The culprit is most likely the high value high voltage dropping resistor inside the HV block. If you run out of adjustment, you'll need to change the block. WES have them.

Of course, could be CRT aging too, NEC were sourcing CRTs out of Canada, not quite as long lasting as the Toshiba CRTs (labelled |NEC) out of Japan.


 
 Return to top of page · Post #: 7 · Written at 10:38:42 AM on 1 March 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 880

Hi All,

Yep Ian, back slides off once you take out ALL the screws (ho ho ho).
The coily thing at the RH back of the pcb has the EHT stuff in it.
2 knobs like you said, screwed the bottom one round a TAD, gave retrace lines, search light brightness.
Backed that off a SMIDGEN and left the letterbox gaps top and bottom almost back to black.
Then noticed focus was a bit blurry on text even with my glasses on.
Went a NATS KNICKER each way on the top knob for best sharpness on the text in the centre.

Then looked at the picture closely, hmmmmm, I think some other things need TWEAKING its got a bit of a "shadow" just faintly over there and the sync has a bit of a flutter and really the black level is just not quite right...…………..and then I stopped thinking and put the back, um back on. I think the viewer needs recalibrating now he can actually see whats going on in the dark bits.

After all, the only thing I watch is "Star Trek Enterprise" over an afternoon cuppa tea and a comedy show called "the national news" on any network . I think they are comedy shows because it always has idiots on it masquerading as politicians and soap stars and it makes me laugh. After that I turn it off although Mrs Lever does watch the Chaser and any Midsummer Murder or Father Brown.
I just go and read a book, write another car/coin/electronic article , or go into the shed and rebuild some car/radio/nuclear reactor thing.

Thanks again , Fred.


 
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