21 Feb
2004
21 Feb
'04
3:36 a.m.
On Sat, 2004-02-21 at 03:48, Tony Duell wrote:
Ahh, fair call - I was wondering along the lines of bad cap or otherwise
in the vertical drive, such that it was the display itself which was
producing uneven deflection (because I can only see vague character
shapes I can't tell if I'm actually missing data, or if there are blank
lines effectively inserted into the display by the monitor itself)
I am not a display expect by any means! :)
Fair enough :) I love the dual-stacking of chips on the memory board!
cheers
Jules
So, the 2T1
has a standard KME as you say - it looks to have correct
horizontal and vertical drive, with the exception that it skips every
few lines, leaving a blank horizontal gap. I can see what look to be
That does _not_ sound like a monitor problem. You're getting missing
video every few scan lines, right? In which case, either you've got some
Analogue signal that's blanking the display _and_ which is locked to the
vertcial sync signal, or you've got a problem with the memory board
(middle board in the cardcage) in the PERQ. How far does it get through the self-tests? What's
the final number on
the DDS display (front of the CPU box) when it tries to boot?
It gets to 999, which I assumed was normal - but maybe not! Maybe the
character data on the screen is telling me there's a video problem, but
that isn't much use if there's a video problem ;)
The display has an unstable shimmering
Ahh, ok.
right margin to it, which definitely looks
analogue in nature.
That may be normal. There's some marginal timing in the vidro circuitry,
and often the right few pixels are a bit unstable :-( At least one of my
PERQs does that... Ahh, yes it
will be. I checked all the connectors and reseated the
boards plus chips - I remember seeing a few socketed ones that didn't
look like they would have originally been socketed.
You'd be suprised. The only chips I _remember_ socketting was an op-amp
on the hard disk analogue PCB.