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Thread: Need some help re: old-school BNC-input monitors

  1. #1
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    Question Need some help re: old-school BNC-input monitors

    Hey guys... I've run into a snag at work, and I'm hoping that someone here can offer a solution. (Sorry - this thread is not laser related.)

    We've got a positively *ancient* distributed control system at work that we use to run a whole crapload of equipment. This stuff is expensive to buy, and even more expensive to configure, so it's not going away anytime soon despite the fact that it's 25 year old technology.

    Ok - the video output of the console driver is standard 640x480 VGA, but the signal is output via 3 BNC connectors. (Normally you see 5 BNC connectors: Red, Green, Blue, Horizontal sync, and Vertical sync.) Well, our particular unit combines the two sync signals and piggybacks them on the green signal. (This is known as "composite sync on green".) We run 75 ohm coax from the console driver to the monitors; three runs of coax for each monitor. (Red, Green+sync, and Blue)

    We've got 4 separate video feeds coming out of this console driver upstairs. Each one runs down to the control room to feed one of 4 large 21 inch CRT monitors. These monitors have the standard 5 BNC input connectors, but they also support the special "composite sync on green" mode as well.

    Three of these monitors are Hitachi CAD monitors that haven't been manufactured since the mid 1990's or so. The fourth one is a replacement that we purchased a few years ago from Samsung. It's the model 1100 MB, and we really like it. (Great picture, 100% compatible, and very economical at only $550.) Unfortunately, this monitor is now out of production as well, and out of stock at every retailer I've checked. Furthermore, Samsung no longer makes monitors that support BNC input conenctors.

    So here is my dilema: I've got 3 more old Hitachi monitors that are at least 10 years old, and one of them is now dying. (The red gun in the tube is shot) So I need to find a replacement VGA monitor that has BNC input conenctors on the back *AND* supports composite sync on green input. This has been... difficult. Can anyone recommend such a monitor?

    Alternately, a better solution would be to purchase some sort of video converter or switcher that would accept VGA input on the 3 BNC (composite sync on green) connectors and output that same VGA signal on a standard 15-pin VGA port. That would allow me to connect virtually any monitor I wanted... But again, finding such a device has proved difficult.

    So, anyone here have any suggestions? I'm looking for either a source for the replacement monitors, or the video converter device. Replacing the hardware that generates the video in the first place is absolutely not an option.

    Adam

  2. #2
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    hey Adam i found this but don't order any thing yet let me ask my partner what he thinks (hes what i consider a video god )
    because i have no experience with this device but he may or may know of something he has used in the past that is better


    http://products.isc365.com/avcat/CTL...&prodid=359516

    --
    John
    VJ AIWAZ

  3. #3
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    so after speaking with my partner he (he didn't know any thing off hand but did say that any of the old multysync nec would work)
    but he told me that magent is a good quality company and that the device i found would work
    --
    John
    VJ AIWAZ

  4. #4
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    Is replacing the tube in the existing monitor out of the question?
    I used to repair monitors and other pc hardware for a living about 10 years ago. It's not too difficult, just be careful to discharge the cathode with a piece of ground wire (under the suction cup). You could consider this as a plan "B" I suppose. We used to have a gizmo that would attempt to recharge a dying electron gun in a CRT by overheating the filament. This had to be done very carefully, because they are easy to fry. Some tubes were more receptive to this than others. I don't know if tubes are easy to procure for the general public, but it might be feasible if finding a new compatible monitor turns into a big hassle.
    -Mike


  5. #5
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    I also forgot to mention that the majority of CRT's that lose one color (from my experience) seemed to do so because of either a cold solder joint, or failed capacitor on the tailboard. The symptoms help determine if it is actually the tube- these usually fail over an extended period, while joints & caps seem to be a little more sudden when they go South. Out of all the monitors I repaired, it seemed like Samsung usually had the shortest-lived tubes. Also, many monitors that say different brands on the outside may really be the identical monitor & tube on the inside. More parts span makes & models than you might first guess.
    -Mike


  6. #6
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    The LG lcd tv 42" has rgb inputs, not sure about the sync.

  7. #7
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    by the way, the three-conductor rgb you're using is most commonly called "rgsb". for your situation, I'd look around for rgsb to vga converters. If you guys are going to hang on to this system for awhile longer, i'd just get four of them now so that you have them as you need to replace your monitors. You can probably get four of them and a 21" lcd for close to the price of a replacement rgsb monitor, if you can even find such a beast (excepting ebay, of course).

    *EDIT* - Duh, completely forgot my original point!

    You may also want to look at some of the newer lcd tv's with component inputs. on some of these you can change the input from y-pr-pb to RGB. I'd say head out to circuit city or best buy and play with the menus, such a tv may offer a direct replacement option.
    Last edited by Mr.Coffee; 02-01-2008 at 01:32.
    "TO DO IS TO BE" - Nietzsche
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  8. #8
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    Smile Thanks guys!

    Wow! Thanks for the great replies, guys!

    John;

    The product you linked to is *exactly* what I was looking for. I need to contact them today and see how much they cost.

    Sam Goldwasser also suggested that I google for "Video Sync Stripper", and sure enough, that search lead me to this product:
    http://www.dvi-extender.biz/products/RGB2VGA.htm
    which is very similar to the one you linked to. I'm going to contact both companies today and compare prices, features, and availability.

    But yeah, Like Mr. Coffee said, purchasing 4 of them now is probably the way to go. Then we can shit-can these heavy-ass CRT's and replace them with LCD monitors.

    Mike;

    Re: replacing the tubes. That is an option, and one that we had considered as a last resort. Didn't think about the possibility of a simple component like a bad cap though. That might be easier to find and fix. (Interestingly enough, though - we've had a total of 3 monitor failures, and it's always the red gun that dies... I think that probably rules out cold-solder joints, but a failed cap makes sense.)

    If we can't get the converter to work, we'll look at repairing these monitors. I can check the caps on the tail board myself. (Just gotta make sure I don't shock the shit out of myself!)

    Still, if we can replace those large CRT's with cheap, off-the-shelf, LCD monitors, we'll be a lot better off.

    Noiseboy, Mr. Coffee;

    Good point re: LCD TV's... I never even considered that. If they'll work with a 31.4 Khz horizontal sync, they'd be fine. I might look into that as a secondary option if I can't get the RGSB-to-VGA adapter to work.

    And again, thanks a million for the great responses guys! (Makes me look good in front of my boss when I can pull a rabbit out of my hat and come up with a solution for all this legacy hardware crap we're stuck with...)

    Adam

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