HP2648A terminal

Tony Duell ard at p850ug1.demon.co.uk
Sun Aug 7 14:27:09 CDT 2005

> HP made the (excellent) HP1350 and HP1351 vector graphics boxes, but
> these have no keyboard input capability.

I have a pair of the 1350s, and as I've mentioned here before, the design 
is strange. They take in a subset of HPGL (that is, commands in ASCII, 
numbers as ASCII-coded decimal digits) and turn them into vectors which 
are then output as analogue X,Y,Z signals. The weird part is that there 
is no processor or processor-like circuit in there, it's all hardwired 
logic. 3 large PCBs of it. I have the service manual.

The 2 10-bit DACs on the 1350 mainboard have preset pots to tweak the top 
6 bits (there are setting up instructions in the manual). For reasons of 
the physical appearance (2 rows of pots) and function, I quickly named 
this the 'graphic equaliser' :-)

Does anyone have the service manual for the companion HP1311 monitor? I 
don't, and I've never seriously looked inside. 

> Vector quality is very very good, better than a DEC VT-11 IMO, but
> the VT-11 is a bit more advanced (more capable).

The VT11 has a resolution of 1024*768, the HP is 1024*1023. Both are very 
good devices for their time.


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