Re: My Apple ][+ is now very, very sad...

[Linards Ticmanis <ticmanis@gmx.de>]

John wrote:

> Quick thought- maybe the PSU is causing some weird interference? (The
> fact that I can get a clear screen if I keep resetting makes me think
> not) I can take the PSU out of my //e to test this. Also, is there any
> chance the CPU from my //e will work in it? Its a 65C02, so I doubt
> it. And the whats keeping the //e from working may as well be the
> processor, so who knows.

Get a schematic and a circuit description (for example from the book
"Understanding the Apple II" which is on the net as a PDF).

Identify which chips are in the video generating circuits. Luckily most
of them are not ASICs as in the IIe and later models, but super common
74LSxx chips that are still readily available. Then buy a bunch of the
right chips and swap away.

With enough time and enough mental effort, a circuit description and a
schematic might even tell you where the error is most likely to be
located. For example, your sync generation seems to be unaffected since
the picture is centered and stable. Have you tried the graphics modes
(blindly type GR, HGR and HGR2)? Do they give the same appearance? If
those work, for example, then the culprit is likely to be in the
character generation part of the video circuit.

Also, there are several 74LSxx chips that occur multiple times on the
board. You can try swapping those around and see if you get an effect.

-- 
Linards Ticmanis