How easy is it to damage an IBM CGA display?

Jim Leonard trixter at
Wed Nov 28 17:55:56 CST 2007

mbbrutman-cctalk at wrote:
> I mistook an IBM Industrial CGA display for a monochrome display, and 
> plugged it into a monochrome display adapter port.  There was no smoke 
> or funny noises, but it definitely did not work.
> I've heard stories about the IBM monochrome displays being fragile when 
> mishandled like this.  Were the IBM CGA displays also this fragile?
> (I won't be able to test it until I dig out a CGA card.  And now of 
> course I'm just paranoid and hoping that I didn't hurt it.)

CGA is 15.75KHz H and 60Hz V; monochrome is 18.4KHz H and 50Hz V. 
That's pretty similar bandwidth, and I haven't heard any stories nor 
personally experienced that doing what you did would release the magic 
smoke.  If you didn't hear a loud high-pitched whine, or smell ozone, I 
wouldn't worry about it.

I *have* witnessed a monochrome monitor releasing the magic smoke 
through software, but the software in question was something that fed 
random values to all of the MDA ports in rapid succession.  Who knows 
what kind of timings (or pulses!) were responsible for blowing it up...
Jim Leonard (trixter at  
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