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Old 27th Dec 2018, 9:49 pm   #1
Michael Maurice
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Default JVC monitor BM-H2000

This monitor was sent to me from Bristol, the owner said that the had a frame issue with a white line across the screen.

When I got it, there was no picture, turning the A1 up didn't make any difference.

It seems there are two HV cables for the A1 or G2 as JVC call it. One comes from the LOPT and one from the scan board. The one from the scan board produces some 450V as does the A1 but the one from the LOPT goes to ground from via a 2.2M resistor. The other one from the scan board goes to the G2.

Now if i swap them round, I get a picture, but I've no idea why.

Next and the reason that the owner sent this to me is the white line at the top of the picture. It is only there when the scanning is set to 16:9 aspect ratio.

I've replaced the diode and capacitor in the frame boost stage but there's no difference.

To me it looks like vertical blanking problem, but I've no idea where to look.

Has anyone got any ideas?
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Old 27th Dec 2018, 11:15 pm   #2
natlock
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Default Re: JVC monitor BM-H2000

Looks like a bright-up first line, most pro-CRT monitors have it, not a fault.
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Old 28th Dec 2018, 1:10 am   #3
John123
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Default Re: JVC monitor BM-H2000

Yes I think it might just be the way it is. I used to own the equivalent Panasonic version (BT-M2090Y), although I don't recall using the widescreen mode. It did have an extended menu for some of the more advanced settings (Size/ Centering for RGB/Component mode, White Balance etc). I recall you accessed it by holding down Enter, and then pressing the Menu button.

I don't think the Panasonic version came with a remote (no IR receiver?), but for picture/ geometry adjustments on the fly, the JVC could take advantage of a dedicated remote control (RM-C550W).

There is also a way to reset the user menus to factory (just in case the phantom twiddler has been!), and also a full separate service menu which can be accessed by following the instructions in the service manual. The Panasonic version manual can be viewed/ downloaded here.
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Old 28th Dec 2018, 10:33 am   #4
red16v
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Default Re: JVC monitor BM-H2000

Are you sure the white dots/dashes are not the Wide Screen Signal (WSS) transmitted on the first half of analogue line 23? by some broadcasters.

Of course we don't transmit analogue telly any more, but I don't know what the source material is your displaying.

As natlock has posted some professional monitors did include a bright up on some of the first lines of the raster to enable the beam current to be measured and reference white to be maintained - Barco did it on their range of monitors for example, but it was a continuous line at the end of blanking and not a series of dashes. Curious indeed.
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Old 28th Dec 2018, 12:17 pm   #5
Michael Maurice
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Default Re: JVC monitor BM-H2000

The source is a Sony DVD recorder, could possibly try playing a non broadcast video, ie home video. I'll also try adjusting the A!.

Has anyone any thoughts on the first conundrum with the A1/G2 cables?
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