Re: IIgs self-test results

[rubywand@aol.com]

In article <travis-2201970114450001@dream-king.cisco.com>,
travis@cluracan.org (Ward C. Travis) writes:

>
>I've run a IIgs through a self-test ....
>
>The system then cycles through a long memory test and terminates, sadly,
>with this display beginning in the upper-left corner of the
>40-column-screen:
>
>   06010000
>     06010000
>       06010000
>
>.. and in the bottom line of the screen:
>
>   System bad: 06010000
>
>And, of course, the speaker emits a piercing bell that must last two or
>three seconds.
>
>So, does anyone know how to read the final code? Is it pointing me at a
>bad port? 


     The system bombed on test #06, which checks the registers and some
functions of the SCC, the Zilog 8530 Serial Controller Chip. Error #01
(the second pair of digits) indicates a failure to pass the Read/Write to
Register test. (Info is from Apple IIgs Technical Reference by M. Fischer,
page 215-216.)



> Is it pointing me at a bad port? Bad DRAM on the
> motherboard? (I recall the original Apple ][ memory
> diagnostic that named exactly which chip had failed..)  ....


     It does not seem likely that your system would pass the earlier tests
of RAM if you had a bad RAM chip.

     Your SCC could be bad; but, a better candidate may be one of the IC's
in the group which produces the RD, WR, and CE signals for the SCC. These
include a 74LS74 (UE13), a 74LS02 (UF9), an a 74LS51 (UD14).  The
schematic for the ROM-01 GS in the 'Hardware Reference shows several Test
Points for this group. This may indicate that the IC's should be checked
when you have "SCC problems".

     If your SCC (a square, 40-pin IC) is socketed, try scootching it up
(using a pin or needle at the corners) just a bit and re-socketing-- do
this with power OFF. If any of the other IC's is socketed, scootch-up and
re-socket each of these, too. This will, usually, fix a poor-contact
problem at one or more pins.

     Sometimes, surface-mounted IC's pop a lead. A lead which lead pops
away from the board may be hard to detect without very good lighting and a
magnifier. If you find a popped lead on one of the IC's, resolder it.  

     Monitoring Test Points while doing accesses to the SCC registers is a
way to determine whether or not _any_ signal is getting to the SCC's RD
(TestPoint 71), WR (TP 70), and/or CE (TP 69) pins. You will need some
kind of pulse detector, like a digital counter or a digital probe.


Rubywand