IBM mono/prn + tandy color monitor?

[Mike Chambers]

hi guys, i'm positive the answer is yes here; however, seeing as i only have one tandy TTL color monitor i thought i'd ask the experts first!

will i hurt anything (will it even work?) if i connect the color tandy monitor from my 1000TX into the output of an original IBM monochrome graphics/printer adapter?

thanks!

 

[Terry Yager]

It wouldn't work, even if it did no harm, which it might.

--T

 

[Mike Chambers]

d'oh! oh well.

 

[Trixter]

CGA is tolerant to vertical refresh rates of 60Hz; monochrome monitors are lower. You can connect a CGA to a monochrome port and no harm should come to it. The opposite is true of a mono monitor to a CGA port.

 

[Terry Yager]

I've done it accidentally both ways with no harm, but I don't recommend doing it on purpose. Mebbe I just got lucky.

--T

 

[Chuck(G)]

CGA is tolerant to vertical refresh rates of 60Hz; monochrome monitors are lower. You can connect a CGA to a monochrome port and no harm should come to it. The opposite is true of a mono monitor to a CGA port.

I was under the impression that it was the horizontal refresh rate that was the real issue. The MDA outputs a horizontal sweep frequency of 18.432 KHz, where the CGA outputs something around 15.575 Khz. Vertical sweep is 50 Hz MDA vs. 60 Hz CGA, but that isn't what toasts monitors.

Many monochrome TTL monitors have no vertical or horizontal oscillators per se--they simply take the sync signals from the MDA and use them to drive the sweep circuits. Most CGA monitors do have oscillators and synchronization circuits, so an out-of-range sync frequency simply causes an out-of-sync display. But putting a CGA output on a TTL mono monitor will likely cause the horizontal output transformer to smoke because of excessive off-resonance current draw.

My first mono monitor with my 5150 was an ordinary generic 15Khz orange monochrome monitor. Changing a capacitor in the horizontal output circuit (and tweaking the height, width and linearity controls) let me use it for several years on a PC. Doing the same with a CGA monitor would probably be more involved.

So, while hooking a CGA monitor to an MDA output won't create magic smoke, it won't sync up either. There are some old Multisync/multiscan monitors (remember the relays clicking in the Sony CPD1302?) that do detect the sync frequencies and make the necessary changes automatically.