18 Jan
2006
18 Jan
'06
9:08 a.m.
On 1/18/2006 at 12:13 PM mbbrutman-cctalk at brutman.com wrote:
I wonder if we're looking at different schematics. In mine, Q204 and Q205
form the buffer stage for the Hsync signal. The emitter of Q205 seems to
be a blanking signal. the collector feeds sync to Q402 (the deflection
oscillator IC).
In mine, Q206 is the 'brwon kludge' I think.
If you look at IBM documentation (especially the
BASIC manuals from the
era) it is clearly listed as Brown, not dark yellow.
Looks like the network around Q204/Q205 is the dark-yellow to brown
translation in the IBM CGA montor. I can scan that part of the circuit and
post it if anyone's interested.
I haven't checked, but wasn't there also special-casing in the EGA BIOS
code to handle the dark yellow=brown case?
I doubt it. I seem to rememebr a PROM in the input stages of the 5154
monitor, which may well have done the same conversion, though.
-tony