Hi group, I want to replace the CRT monitor in my 8924 and bought a GBS-8200 board. Well I saw a picture where they plugged it into the green (Y) rca jack on the 8200 board and this worked to a degree but the display was black and white and the right hand side was cut off. I tried the vga/ega connector without a sync and nothing,?reading another article and blog they used a lm1881 sync separator to extract the V and H syncs. ?So here are my questions
1. does the composite video on a HP 9824c ?have the Sync pulses in it? ?(The article was for a different HP analyzer)
2. The schematic shows the V and H sync pulses are already at the CRT monitor plug can I use these pulses?
3. it there any other way to connect or modify the board to make it work?

It seems like a lot of the info was lost in the move from Yahoo to here like a lot of my other groups so I’m getting bit and pieces. The reason I want to replace the crt monitor is because it has a lot of burn in on the screen and it is only time before I have problems with it. Plus LCD screens are easier to read on my old eyes.?

thanks, Bill N7OQ

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Bill

Here are a couple of old things i saved re getting the GBS-8200 workings with 8924 from the old Yahoo groups.

There is also one on power supply repair plus some notes on power supply caps I replaced a while back - maybe useful for ordering replacements.

73s om de chris zl1cvd

Wow again, great information, I get my lm-1881 Thursday or wed. Will let you know how it works out, thanks everyone,
Bill N7OQ

The 50k resistors, how critical is that value, I have 47k and 56k will either of these work? I guess I could use 2x100k if needed.?

Bill N7OQ

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either will work.

I didn't use them, and it worked...

Em 18/04/2021 22:02, William Verstelle escreveu:

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Ok thanks I’ll try none first then add if needed. Got chip already mounted on a board today so will try is soon.?

thanks Guys!?

Don't forget to post your results here =)

Em 19/04/2021 19:54, William Verstelle escreveu:

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Follow up: well I finally go to test it and it worked OK except I noticed after about 30 minutes it was dimmer. If I kill power and restart it it come back on bright. It never went away totally so I’ll add the resistors and see if that helps.?

another thing if I used the menu on the board to center adjust size etc I lose the settings once power is removed. So not sure how to save the settings. ?

thanks Bill N7OQ

Hi all,

I've been reading this thread with interest as I would like to get my 8924C screen to work on an external monitor.

I was wondering if it is possible to just use an LM1881 to separate the syncs from the composite video out and feed them directly into the H & V inputs of a multisync VGA monitor which covers the 19.2KHz frequency? Has anyone tried it? Is it likely to work, or do I definitely need the GBS8200 effectively as a frame-store to shift the text to the right? Many monitors have an auto-adjust setting which centres the picture automatically, so that may work.

Thanks,

Frank.

I use a Sony?DSC-1024.? It will convert any video format to any other very easily.??

Hi,

Thanks but the DSC-1024?are a bit rare and expensive second-hand, so I'm looking for a cheaper and simpler solution if there is one.

Hi Frank,
What do you mean by "multisync VGA"? If it is genuinely capable of running at 19.2 kHz, not 31.469kHz, then yes a you can use a? LM1881 to separate the sync and feed that and the video to the monitor (video to green input). however a modern monitor that will run at 19.2kHz is a rare beast. I don't know of any, other than broadcast monitors that effectively have a standards converter built in. The ORIGINAL NEC MultiSync CRT monitors will work. You don't even need a sync separator, they accept composite sync on green (SOG). However the later ones just used multisync as a model name and are normal VGA 31.469kHz. This includes, as far as I know, all the LCD ones. For example 31.5kHz to 81.0kHz

Where are you located? I might be able to help with a converter.

Robert.

Hi Robert,

Thanks for your reply.

Yes, it was the original NEC Multisync monitors I was thinking of. I have seen some on fleabay but didn't realise they would take full signal on the green input without separating the syncs first per the VGA standard. OK about some CRT types only that will sync at 19.2KHz - I didn't realise that. Yes I suppose a multi-standard broadcast monitor would do the job, but they're not cheap. Just out of interest, what "Standard" is the 19.2KHz o/p of the 8924C video and is there a particular reason for it?

I've got a few different monitors I can try on the off-chance one might work, and was also going to see if a device I've got called an "Easycap" might work. It's a USB capture device for transferring video to a PC so it's worth a try. Being a cheapskate,?

I'm in Long Sutton, South Lincolnshire and collected the 8924C from you a while back.

Regards,

Frank.

Hi Frank,
If you are back this way anytime I have a converter you can have. VGA output.

Robert.

Hi Robert,

Thanks, that's a very kind offer which I'd like to accept.

I've still got your details, so I'll contact you direct as I may be able to call by on Sunday 19th late afternoon/early evening if that's OK??

Thanks and regards,

Frank.

Hi Alexandre,

I followed your build and it kind of works, but my display is nowhere near as sharp as yours. I can't get my display centered vertically and there's lots of garbage below the image and floating around the screen.?

I've screwed around with the settings *A LOT* and I think the "clamp st" and "Clamp sp" values might be the answer.? Can you share you settings from the Geometry menu?

My monitor is a Viewsonic 10725 which has a native resolution of 1280 x 1024.? I've used it successfully with dozens of other computers @ 640 x 480 as well as other resolutions and it always looks great.

I've tried all of the available resolutions in the display menu and I can't say another are better than the others.

I have an 8924c, not an E8285A, perhaps they aren't the same?

73's Skip WB6YMH

I've tried