MDA to VGA convertor / adapter - Page 1
Forum section: electronics / repair

author: free_electron
author_rank: Super Contributor
timestamp: November 12, 2014, 03:52:55 pm
content: I have endeavoured at replacing the pictures tubes in some test equipment ( 3588 Spectrum analyser , 3589 Network analyser and 35665 Dynamic signal analyser. (i'm on a crusade to eradicate the last remaining 'vacuum glass balloons with metal scrap in em' from my lab, i have one that is very dim so it has to go )I have established these are MDA monitors. ( old skool IBM style monochrome display adapters , essentially hercules at 720x350 pixels.They have a hsync, vsync , video and brightness signal ( 2 level brightness , video toggles black / white , brightness controls 50% , 100% white)clock is 18Khz like MDA.I have found nice 9 inch LCD panels with 800x600 pixels that will fit the existing machine body nicely. these have VGA input and run of 12 volts ( the existing monitors also run off 12 volts, so that is a nice fit too )so i need a MDA to VGA scan converter. those things are expensive on fleabay ... you can get cheapo 30$ scan convertoers for EGA / CGA to resurrect old gaming machines . i wonder if those can handle MDA in any way.Anyone has an idea , or better : anyone has a schematic ?

author: Shock
author_rank: Super Contributor
timestamp: November 12, 2014, 09:31:27 pm
content: This may interest you. I'm sure there is more on this elsewhere.http://aknamunka.uw.hu/mdah/1st.html

author: krivx
author_rank: Frequent Contributor
timestamp: November 12, 2014, 10:46:49 pm
content: Simmcomm sell some rather expensive (~400usd) kits for replacing the HP 1345a displayhttp://www.simmconnlabs.com/2136.htmlThe manuals show a small CPLD/FPGA board between the two. You might have to follow this custom route...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 12, 2014, 10:58:17 pm
content: Should be pretty straightforward with a FPGA and SRAM.Might also be doable with a fast MCU that has an LCD output and camera input - I think there are some STM ARMs that do.The fact it's only 2 bits per pixel means the bandwidth is pretty low, and may allow for some sneaky tricks like using SPI ports as video in/output shifters

author: free_electron
author_rank: Super Contributor
timestamp: November 12, 2014, 11:10:28 pm
content: Quote from: Shock on November 12, 2014, 09:31:27 pmoverclocking is out of the question. this may be MDA but it is generated by a highly specialized motherboard. i am NOt messing with that !

author: free_electron
author_rank: Super Contributor
timestamp: November 12, 2014, 11:16:58 pm
content: Quote from: krivx on November 12, 2014, 10:46:49 pm'yeah , those are for the vector displays in the really old crufters. not what i'm after ..

author: free_electron
author_rank: Super Contributor
timestamp: November 12, 2014, 11:19:06 pm
content: This si a problem that frequently pops up. lots of CNC machines and other industrial kit uses MDA monitors. There is a market for these things but the prices are jacked up artificially high. ( of course ,since they want to fix 100k+ machines ... )i don't believe for a second the 'guts' cost 400$ ...anyway i found a converter on ebay for 170$ and ordered it . i'll find out what makes it tick and duplicate it ( if possible)

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 13, 2014, 01:10:25 am
content: Hm, just off the top of my head,http://www.averlogic.com/product_video_converter.aspmaybe trick one of these chips to convert the 18KHz MDA "VGA" to NTSC, then use a cheaper NTSC to VGA adapater.http://www.datasheetcatalog.com/datasheets_pdf/A/L/1/2/AL128.shtmlCan't figure out if it would work with the 18KHz , that's not a VGA sync rate. Looks like you have to calculate some values and see if the chip goes that low...Wiki says this one worksGBS-8219http://www.ebay.com/itm/GBS-8219-XVGA-Box-CGA-EGA-RGB-RGBS-RGBHV-toVGA-Industrial-Monitor-VideoConverter-/121422218582?pt=US_Video_Cables_Adapters&hash=item1c45540556

author: free_electron
author_rank: Super Contributor
timestamp: November 13, 2014, 09:56:48 pm
content: Nah. i want a ready made module. Unless it's 3 resistors of course.I'm going with the module i found now for 170$. probably not worth it trying to make such a thing myself. i can get the lcd panels for 30$ ...So the entire retrofit will cost 200$ .. perfect. i have one dead monitor and one close to end of luminosity. ( it's well below 50% of the good one )Time to toss em out and stick LCD's in. i hate anything vacuum tube related.. picture tubes are the least remaining evil.

author: nctnico
author_rank: Super Contributor
timestamp: November 13, 2014, 10:20:56 pm
content: Quote from: free_electron on November 12, 2014, 03:52:55 pmWhat I usually do is build my own scan converter from a CLPD and an SRAM. In some cases you can be lucky and the signals can be made compatible with the TFT display.