Re: Apple II+ Flakey Inverse Characters

[mwillegal <mike@willegal.net>]

I think that you are on the right track.

A flakey 2513 was my first guess, but you indicated that it only
happened
in inverse mode.  This problem should not be dependant upon mode,
though it
may be more obvious in certain modes. I had a batch of NOS 2513 chips
where
about 50% of them had this issue.

Regards,
Mike Willegal

PS
the 341-0036 character rom part listed on the site you mention is not
a 2513 and is not compatible
with early Apple II motherboards.

On Jan 7, 9:13 am, wrodiger <wrodi...@gmail.com> wrote:
> On Jan 4, 3:29 pm, wrodiger <wrodi...@gmail.com> wrote:
>
> > On Jan 4, 1:07 pm, dog_...@macgui.com (D Finnigan) wrote:
>
> > > wrodiger wrote:
>
> > > > Thanks in advance for any help,
>
> > > Here is a repair guide which may help:http://macgui.com/kb/article/759
>
> > Thanks, I'll take another look through this. I reseated and swapped a
> > few of the IC's mentioned here to no avail the other day.
>
> > Will
>
> Update: I reseated all chips involved in the text display generation
> to no avail. Further analysis showed bad characters in both INVERSE
> and FLASH mode. I then went through the text display section of Jim
> Sather's book "Understanding The Apple II" which describes the logic
> at gate level (great book by the way!). Based on my analysis, I have
> determined that this is likely a bad Character ROM because the bad
> bits within the characters on the display are at stationary points
> within the characters. By my reasoning, and looking at the bit
> shifting circuitry, this points to the ROM as the source. I ordered a
> replacement from arcadecomponents.com (a good source of replacement
> parts). I'll post an update when I receive this replacement and test.
>
> Will