15 Dec
2009
15 Dec
'09
11:33 a.m.
I just received a trs-80 model II over the weekend :-)
I have never used a model II before.
It looks like there is some kind of problem...here are the symptoms:
When I turn it on, the screen is all inverse exclamation points "!".
It says "INSEST!DISKEUTE"
When I close the diskette door, the exclamation points turn non-inverse
but still cover the screen.
It when boots (in this case I am booting a cpm disk).
The letters seem jumbled up...after booting, I see:
"CQ/MQ!for!tss-81 MOEM II
63k!Version!2/25A
Copyrigit!(c)!1981 Migecoat Associaues"
And it goes to a command prompt.
The rest of the screen is still filled with exclamation points.
The system does respond as I type things, but letters are garbled.
Any ideas? Does this sound like some bad memory? How can I diagnose
this?
By 'inverse exlamation points' do you mean they're in inverse video?
It appears there's something wrong with the video data. At least bit 0 is
stuck high (that would turn a space into a '!', a 'P' into 'Q',
and so
on). If it's in inverse video too, that may mean bit 7 is stuck, but I
don;t know the M2 that well.
It could be video RAM problems (that's the most likely), or a prolem with
a buffer chip or similar in the video circuitry. I don;t like lucky-dip
debugging, but if you can find the video RAM (most likely to be small-ish
static RAM chips), try replacing them.
-tony