1. Home
  2. Electronics Repair
  3. NEC 3D image collapsed vertically

NEC 3D image collapsed vertically

Hello.

I'm the owner of an old NEC 3D monitor (I bought it around 1988 or so), and it was working fine till I stopped using it for a few months and switched it back on yesterday... Suddenly, the image collapsed vertically: the bottom half is still readible and apparently not too distorted, but the top half lines have collapsed to a mere 3cm high band, in which the text even appears inverted (upside down) for the top lines.

I opened the monitor and checked for the trimmers (dirt may sometime be responsible for false contacts) and for any defect that would be visible (exploded or leaking capacitors, burnt resistors, diodes or transistors), but I found nothing wrong. Before I spend more time investigating, did anyone else already encounter such a problem and/or could give advice as to where to direct my investigations ?

This monitor is the only one I got that is capable of displaying old computers images (15Khz Hsync), and I do need it...

Many thanks in advance !

Thierry Godefroy.

Reply to
anonymous
Loading thread data ...

I'd start by getting a circuit diagram, then you can check varous voltage points in the horiz scan section.

none of your newer ones will do 15kHz horiz? I'm surprised, most bog standard 17" ones will do that.

NT

Reply to
meow2222

On Mon, 19 Feb 2007 19:18:22 +0100, anonymous put finger to keyboard and composed:

Look for dry electrolytic capacitors in the vertical section. Otherwise, if your chassis uses discrete transistors for the vertical amp, then check those. The worst case scenario is a bad yoke.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

Or if you want a working NEC 3D I'm about to toss.....

--- sam | Sci.Electronics.Repair FAQ:

formatting link
Repair | Main Table of Contents:
formatting link

+Lasers | Sam's Laser FAQ:
formatting link
| Mirror Sites:
formatting link

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Reply to
Sam Goldwasser

Not any I've seen that were made in the last decade or more. The last VGA monitor I had that was capable of 15 KHz was a Sony CPD-1302 made circa 1988.

Reply to
James Sweet

anonymous ha escrito:

classic symptoms of bad caps in the vertical section. just replace them

-B.

Reply to
b

I stand corrected, had forgotten to take interlacing into account. Can the OP not use a TV?

NT

Reply to
meow2222

Thank you (and everyone else) for your advice. I indeed think it has something to do with a bad capacitor or transistor... Alas, without a schematic, it's like searching with blindfolded eyes. I therefore wrote to NEC, and I hope they will provide me with a schematic...

Regards,

Thierry Godefroy.

Reply to
anonymous

On Thu, 22 Feb 2007 20:16:37 +0100, anonymous put finger to keyboard and composed:

I don't know if it's the same beast, but a service manual with circuits for an NEC Multisync 3D (model JC-1404) is available for free download (in four parts) from here:

formatting link

If your monitor has an LA7835 vertical output chip, then change the capacitors nearby.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

WOW ! Cool ! Many thanks: that's excatly what I was searching for ! :-)

Best regards,

Thierry Godefroy.

Reply to
anonymous

was this the one that the electrolytic capacitors leak and hurt traces on the multi layer main board...

if you see physical, electrolyte leakage on the board, it is, and you must be careful because the traces are very small ... usually require jumping some with wire...i tried to get one going once like this and i gave up ... the degree of damage can vary alot and mine was a pretty bad one

Reply to
jonpi

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.