Late-model Hercules card

[Jules Richardson]

On 04/20/2015 07:50 AM, tony duell wrote:
>>
>> display? Given the date I just want to check that it's not one of their CGA
>> or EGA compatibles.
>
> You don't need to trace much to figure out what it is (assuming it's standard [1]).
>
> First check if pins 1 and 2 of the DE9 are solidly grounded. If pin 1 isn't, it's something
> strange. If pin 2 isn't (but pin 1 is), it's likely to be EGA [2]. If they are both grounded, then
> it's likely to be MDA (hercules) or CGA.
>
> Now check if pins 3,4,5 are connected or floating. The diode check range on a DMM is
> useful here, try it both ways round between the pins and ground. If all are floating, it's MDA,
> if they are all driven, it's CGA.

Thanks Tony, looks like it's straight MDA, then - 1 and 2 are grounded, and 
3,4,5 are n/c.

I'm still surprised that there was a market for new Hercules boards in 
1990, although I suppose it's possible that it was part of a batch made for 
a specific contract. That 4" of bare PCB is just weird, too, perhaps 
suggesting that it was made for a specific application where having the 
card secured at both ends was useful.

cheers

Jules