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 Using a modern VGA monitor on old XT or similar View next topic
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BB



Joined: 07 Apr 2005
Posts: 2
Location: Greytown, New Zealand

PostPosted: Thu Apr 07, 2005 2:39 am Reply with quoteBack to top

Our local garage has a pump computer (around 1990) that indicates the amount of petrol taken from each pump. It used a 1989 monochrome monitor similar to a green screen XT (9 pin DB9) but that has died. Is it possible to make an adapter to use a modern PC monitor? I realise that the old monitor is probably TTL level sigs and the new one is analog level but is there a difference in sync signals as I have tried wiring a 9 to 15 pin adapter(1-1, 2-2, 3-3,4-13,5-14,6-6,7-7,8-8,9-10and11) but that didn't work.
Message on Phillips monitor was "No input sync". I seem to vaguely remember that the IBM PC only used pins 1 and 2 and 6-9 and often had pins missing on the plug but the engineer for the petrol pump supplier said that you had to use all 9 pins and was dual phase or twin phase or some other phrase that didn't make a lot of sense to me or him but this was what he remembered from some older engineer telling him who obviously knew about the details - he didn't.
Any advice would be much appreciated.
Very Happy

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Puckdropper
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Joined: 02 Oct 2004
Posts: 760
Location: Not in Chicago

PostPosted: Thu Apr 07, 2005 5:00 am Reply with quoteBack to top

If it uses standard ISA or 16-bit ISA you can plug in a new video card and use another monitor. If not, you may need to look in to getting one of the early NEC MultiSync monitors that does support the many modes.

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T-R-A



Joined: 02 Oct 2004
Posts: 578
Location: Western NC

PostPosted: Thu Apr 07, 2005 6:40 am Reply with quoteBack to top

FWIW---(and probably don't need to mention this) but you can destroy an adapter and monitor if you're mixing TTL and analog...

The cheap and dirty would be like Puck said, find an ISA card off of an old machine and put a newer monitor on it...
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wdegroot
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PostPosted: Fri Apr 08, 2005 5:05 pm Reply with quoteBack to top

nooo problem
many older isa vga cards will work in an 8 bit slot
I have read a manual for an advanced 16 bit ATI video card that SAYS it will work in a 8 but slot
just do 2 things.
1) swicth themn video to NONE or EGA ( same settings) sw 5&6?
and use a bit of tape to prevent the extra fingers from shorting out in the motherboard
remamber all the slots in a real xt are the same EXCEPT the one closest to the poser supply. you can move cards around.
plan 2: sent me postage/mailing as i have a bunch of old green and yellow monitors.

but plan 1 is better.
while we are on the xt subjest. a 1.44 drive will work in an xt.
a 720k floppy disk formatted as 720k will boot and be recognized as a 720k
but best to save a bunch of 720k floppies and format them as 360k.
these are more relaible than the 5.25" floppies. mark each as a 360
no mb switch setting changes are needed or possible!
wdegroot
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PostPosted: Fri Apr 08, 2005 5:07 pm Reply with quoteBack to top

no i guess you don't want to ship an old monitor to NZ!!!!!!1
BB



Joined: 07 Apr 2005
Posts: 2
Location: Greytown, New Zealand

PostPosted: Sat Apr 09, 2005 9:30 pm Reply with quoteBack to top

Thanks for the advice. Pump computer is a special manufactured device - does not even have slots so not possible to swap cards etc. But problem is solved. We found another garage that had upgraded to a more modern system and had three monitors of the original type, so we bought the lot for $75 and all are still working.
Thanks for the warning T-R-W but it should be possible to wire a small interface that correctly reduces the 5V TTL to the 700mV required for the analog. After all we were only trying to display text - no need for color, greyscale etc. I vaguely remember that Steve Ciarcia of Circuit Cellar fame in Byte magazine addressed this in the early 90's but can't find the article (even from the web archive). I think it had only resistors and diodes - no active devices.
Very Happy

_________________
Old Computers are not Junk. They are just waiting for a new use to be found for them.
(or so I keep telling my wife)
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T-R-A



Joined: 02 Oct 2004
Posts: 578
Location: Western NC

PostPosted: Sat Apr 09, 2005 10:08 pm Reply with quoteBack to top

It's T-R-A, not T-R-W (I used to work for TRW, hated it.....)
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Guest






PostPosted: Sun Apr 17, 2005 5:17 am Reply with quoteBack to top

It was addressed but the problem is you need a very old VGA monitor, not svga and you need to mess with the frequency dials inside along with a simple voltage reduction ciruit. (remember most SVGA screens won't go down in the basement on horizonatal sync)

Remember though your screen will only be half size also and usually can't be enlarged. See if I can find the article... Also on a side note monochrome usually had about 3 shades black white and gray (or 50%) on a vga screen you would get Black/Green/ and maybe Blue or red if you hook up the gray pin on your vga screen.

UNLESS you find an old VGA monitor that says TTL compatible in the manual like my old Packard bell screen, then a simple adapter works without anything messy.

Good Luck
Guest






PostPosted: Tue Aug 30, 2005 8:29 pm Reply with quoteBack to top

This is what you need, a barnd new monochrome monitor.

http://www.miraclebusiness.com/mono.htm

That's the manufacturer's page.

You can purchase one here, for $129:

http://www.totalbarcode.com/Product.asp?ProductID=204&src=pw
Pimped_Portable



Joined: 30 Aug 2005
Posts: 20
Location: Gurnee, IL, USA

PostPosted: Wed Aug 31, 2005 2:44 am Reply with quoteBack to top

Aww drat, I'm not used to this guest posting crap. That was me in the last post.
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