2017-10-17 13:56 GMT+02:00 Dominique Carlier via cctalk < cctalk@classiccmp.org>:
> 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 I don't know anything about the system you are about to repair but it make use of a standard CPU which is kind of useful when the schematic is missing. If I were you I would attach my trusty logic analyzer over the CPU to try to trace what it is doing. Which ROM does it access when it is doing the power up self test? Use a disassmbler on that particular ROM and work out what flow the CPU takes in the ROM contents and try to understand what causes it to take the decision that something is broken. Since my logic analyzer has fairly limited memory depth I would have it to trigger on for example accessing the SIO. /Mattis > > > > 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 >>>>> >>>> >>>> >> >> >
