Electronics > Repair
What more i can do?
222Lab_Test222:
--- Quote from: Harry_22 on December 25, 2024, 02:03:40 am ---
--- Quote from: m k on December 20, 2024, 03:31:57 pm ---
We can also be pretty sure that Harry didn't do any mistakes.
--- End quote ---
@222Lab_Test222, when the time permits check our measurements.
Measure directly on the chip pin. Start with non-working board IC16 data.
--- End quote ---
The datas are same, no change at all
m k:
Earlier data width and low address decode signals were rational.
Data signals of swapped ROMs compared to original position ones were not.
Change your approach.
For now you are concentrated to diagnose, change to repair mode.
Your goal is to repair, any board, not the board.
Check all faulty boards.
Swapped ROMs and data lines is one possibility.
That earlier A4 also.
If operation is similar to original faulty board change both ROM sockets, three chips inside them and DIP switch pack.
Logic chips are easier if sockets are off, DIP switches and sockets are general suspects, all are cheap.
Don't hassle, be sloppy or how ever you like to call a robot like function that is very easily happening when you do same things over and over again.
You can be fast all but that fraction of time when you must be slow, one of those moments is when you reseat components.
Don't operate simultaneously more boards than you have a good space for.
Tag everything so that you can be sure what is what, Roman numerals are good if space is not tall.
222Lab_Test222:
Looks like i need to again start from zero BUT keeping all the infos i get in mind.
asis:
Hi,
I would suggest you to hook on a more reliable synchronization source than IC1 MB3771 pin8 (Reset).
Which one?
Until there is a fragment of the circuit - I don't know.
-
Maybe you shouldn't overload the forum with pictures, maybe it's enough to write down in BIN or HEX form, those values on the pins that you will take from the buses during the measurement, i.e. get a data stream in the form of a virtual logic analyzer?
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There will be a number of questions about the circuit...
m k:
--- Quote from: 222Lab_Test222 on January 06, 2025, 01:17:39 pm ---Looks like i need to again start from zero BUT keeping all the infos i get in mind.
--- End quote ---
No, you just change the mode for a moment.
Your ROM data measurements indicate that the CPU has no ROM access at all.
CPU is socketed and ROMs also, the environment of use is possibly hostile.
It's an educated guess that some socket contacts are or have been bad and have possibly taken some logic gates with them.
Diagnosing that is difficult without proper tools.
So the short cut is to change all easy targets, changing few bits too much is not an issue.
But first you must check how common problem this no ROM access is.
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