Re: Weird lines down the display

[David Wilson <david@uow.edu.au>]

Alistair J Ross <mail@ataliross.co.uk> writes:
>  I have obtained a EuroPlus mainboard in working order. I don't recall
>touching the mainboard and causing any damage, but now when it starts up,
>I get straight lines down the screen in text mode. I can still see the
>text on the screen but the text remains. The machine seems to be working
>fine otherwise. If I switch it to graphics mode with 'GR' - the lines
>dissappear apart from the text area at the bottom of the screen.

Do you have 40 one pixel wide lines spaced at 7 pixel intervals?
If so I would check the chargen (reseat the IC as one of the output
pins may not be making a good contact with the IC socket) and the
parallel to serial chip (74166) [reseat it as well] as these are the
only two chips that have the text video data in parallel form.

>Is this a faulty display ROM or could it be a problem with the monitor?

Possible (ROM) and extremely unlikely (monitor) as you say the lines go
away in GR mode - the monitor is just displaying dots - it cannot tell
if they are text dots or graphic dots...

>Why would the problem not initially show it's self and then show now?

Failures have to happen sometime :-(

>Anyone seen a problem like this before?

No.

>PS: Where is the video rom on a EuroPlus?

Same place as on a US II+. Location A5 according to the Red Book (next to
the keyboard socket). I don't recall it being moved in later revs of the
motherboard. It should be labeled on the motherboard - 2513 if pre rev 7,
CHARGEN if rev 7 or later (this is from memory so I could be wrong). Anyway,
it is a 24 pin IC that is not one of the D0 through F8 ROMs.
-- 
David Wilson  School of IT & CS, Uni of Wollongong, Australia