21 Sep
2010
21 Sep
'10
7:25 a.m.
On 9/20/10 9:16 PM, Nick Allen wrote:
Also, Eric Kudzin spent some time trying to fix the
CRT, we are making progress and as part of the testing we need to test a KNOWN WORKING
computer on the Alto
totally incompatible.
The Alto monitor timing is pretty unique. The display is portrait, 606 x 808 with
the high frequency scan from top to bottom. Overheating and horizontal deflection
failures are very common in Alto monitors. The most common cause of failure is that
the horizontal width coil overheats and unsolders itself from the PC board. Because the
horizontal scan occurs across the narrower dimension of the tube, a lot of power is
dissipated in the width coil. It also burns up the paper tube it is wound on, making
it impossible to adjust the width. I ended up rewinding a bunch of them recently using
new coil forms and heavier wire.
Horizonal and vertical drive are hardwired in the display hardware. You won't get a
raster until the display microcode is loaded and running, though, and you have a long
way to go before you're that far.