Re: I killed it.. :-(

["Mark Cummings" <figjams@primus.com.au>]

In addition to Mr. Dog's advise (no offence) you could try arcing it up with
only RAM installed in the lower 16K bank (if you can identify which 8 chips
that is). Try swapping out chips until the garbage on the screen gets
better.
If you have access to a working II+, and if (a big IF) it has the same RAM
chips (4116's IIRC) you could try 7 or 8 of your suspect RAM chips at a time
in the middle row of the II+, then turn it on and type HGR2 <RETURN>. If the
screen clears they are likely good. Only 7 of the 8 chips in the middle row
are displayed as pixels on the screen, the other chip is used to indicate
the colour of the next 7 pixels. That's a real long story, but this is the
short version. If OTOH you get vertical stripes or dotted vertical stripes,
then you have a bad chip or two in that row.
Do this for all your RAMs until you are sure they are all good. While you
are at it try your CPU in the II+. If that all checks out good then
obviously something else has been damaged, and without a circuit diagram you
are going to have to keep guessing.

Mark


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In article <Pine.GSO.3.96.1010730164457.6021A-100000@top.coli.uni-sb.de>,
Linards Ticmanis <ticmanis@coli.uni-sb.de> wrote:


>On Mon, 30 Jul 2001, Mark Cummings wrote:
>
>> 
>> You could try another processor, even a 65C02 just to see if it's that.
By
>> the description of the garbage on the screen, I would be more inclined to
>> suspect the RAM. If it's socketed like the II+ you could try swapping a
bank
>> of 8 around and see if the screen garbage clears up or changes. 
>
>Thanks. Unfortunately that does not seem to be it. Since the computer
>currently behaves exactly the same no matter if there is a CPU in it or
>not, I still assume that the CPU is the problem. By "flashing" characters
>I meant the kind of things that you can get by typing FLASH from BASIC,
>not characters that hop around randomly, so I doubt the RAM is really the
>problem. I exchanged the lower bank with one of the others anyway, apart
>from the fact that now closing square brackets occur more often among the
>garbage nothing has changed. 
>
>I have already run ads looking for broken VIC-20s and CBM 1541 drives in
>our local free adspapers, those have socketed 6502s and also the 6522s I
>need for the mockingboard, unfortunatly I had no success so far. Ordering
>them via mail order seems to cost about $13 per chip which I think a bit
>excessive.. oh well. 
>
>Thanks anyway,
>
>Linards Ticmanis
>