Hi guys!
Nobody here has any information to help me to solve my problem?
Do you think I should talk about this breakdown on another forum? If
yes, have you an address to recommend me?
Thanks
Dominique
On 15/10/2017 23:12, Dominique Carlier via cctalk wrote:
Hi everybody,
As I have no documentation / schematics I started to look for computer
schematics where it is about Z80 and “serial I/O channel B”, I found a
lot of data about this subject that I do not know at all.
These information would allow me to better target the breakdown, if
any of you would consent to pass on some of his knowledge.
In all documentation on Z80 based machines, I find the same elements,
similar architectures: CPU, PIO, CTC, SIO.
http://www.z80.info/gfx/nascom1main.gif
http://www.ep128.hu/Sp_Konyv/Pic/SIO_11.gif
I interchanged with the IC of my other CPU board which are of the same
model.
http://www.zeltrax.com/classiccmp_forum/sio_issue_01.jpg
But the error persists, so the problem is around.
I'm trying to find out why the SIO detects a problem on the channel B.
How does this detection system work? What are the solicited ICs? Do
they communicate through other ICs like multiplexers or others?
I would also like to simulate the absence of this problem in order to
see if this allows my UTS to have a successful POC test, to have again
access to the setup page of the machine.
Is it possible to do something at the SIO pin 30 (W/RDYB) to pretend
that the B channel is OK?
http://www.sbprojects.net/projects/izabella/assets/images/sio1.jpg
Can we imagine that the problem would be at the level of what checks
channel B and not channel B itself?
I also read a lot of obscure thing about memory, and I still wonder if
a memory problem could also play a part in this failure? You must
understand that I continue to try to troubleshoot this machine like
the others, comparative logic without advanced academic knowledge, a
challenge every time.
It's even harder because I have trouble identifying the components. I
do not find any results concerning the 3/4 of the ICs, as for example
these:
http://www.zeltrax.com/classiccmp_forum/sio_issue_02.jpg
And even for components like this, "AVX 224Z 8238"
http://www.zeltrax.com/classiccmp_forum/sio_issue_03.jpg
(ceramic capacitor of 220nf 50v? not sure)
There is also the fact that the tracks are not visible on the CPU
board which I try to repair, so I try to locate myself by comparing
component location to the original CPU board, in short a beautiful mess.
Meanwhile, I restore this beautiful Key Tronics keyboard which was in
a very sad condition. Here are some pictures of this restoration (work
in progress)
http://www.zeltrax.com/classiccmp_forum/keyboard2_01.jpg
http://www.zeltrax.com/classiccmp_forum/keyboard2_02.jpg
http://www.zeltrax.com/classiccmp_forum/keyboard2_03.jpg
<http://www.zeltrax.com/classiccmp_forum/keyboard2_03.jpg>
http://www.zeltrax.com/classiccmp_forum/keyboard2_04.jpg
http://www.zeltrax.com/classiccmp_forum/keyboard2_05.jpg
<http://www.zeltrax.com/classiccmp_forum/keyboard2_05.jpg>
http://www.zeltrax.com/classiccmp_forum/keyboard2_06.jpg
<http://www.zeltrax.com/classiccmp_forum/keyboard2_06.jpg>
http://www.zeltrax.com/classiccmp_forum/keyboard2_07.jpg
In any case I hold on, restarting this machine has become an
obsession, but without help I will still be on it for the next 10
years, thus HELP! ;-)
Everything would be perfectly fine if most of the time I did not have
at startup an error at line 9. of the POC test:
SERIAL I / O CHANNEL B: FAILED
