Electronics > Repair

What more i can do?

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Analog Kid:
Pardon my intrusion into this thread--I'm by no means qualified to comment at all on any of your diagnostic procedures here--but I've been following this whole excruciatingly painful process from afar. Just one question:

Has the OP gone through the board, removed any socketed chips, and thoroughly cleaned the contacts (at least on the chips if not the sockets) before reinserting them?

222Lab_Test222:

--- Quote from: Analog Kid on January 07, 2025, 10:31:10 pm ---Pardon my intrusion into this thread--I'm by no means qualified to comment at all on any of your diagnostic procedures here--but I've been following this whole excruciatingly painful process from afar. Just one question:

Has the OP gone through the board, removed any socketed chips, and thoroughly cleaned the contacts (at least on the chips if not the sockets) before reinserting them?

--- End quote ---
Yes it has done multiple times.
I always clean with isopropyl alcohol.

SMdude:
I'm not sure if this has been covered, it probably has, but I have not read the whole thread.

The 74ls245's have you replaced these on a non working board?

Have you tried replacing all easily obtainable(and fittable!) parts on a non working board?

Sometimes for the cost of the parts involved and time to fit vs the time to actually diagnose which exact part is causing a fault it is better to just replace parts until it works or not! Also by replacing parts you can rule out which parts are not causing the problem.

m k:

--- Quote from: 222Lab_Test222 on January 06, 2025, 04:35:29 am ---
--- 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

--- End quote ---

I'm not sure that you are as accurate as you should.

If you're not changing components yet do ROM data measurements again twice.

First take chips out and measure if you can find any rational connections between ROM socket and inside socket ICs.
(skip pins that you already know are not connected)
Any of socket pins 10, 11, 12, 22 or 24
to
any of F32 or HC125 pins 3, 6, 8 or 11.

Then put ROMs to their correct positions and measure data lines as you did earlier.
Compare old and ne results with strict and pedantic way.
Don't concentrate to timing, concentrate to width of down period,

If your earlier measurement was something else than CPU pins then measure data lines again from CPU pins.
Are they same or just similar?

Then put ROMs to their swapped positions and measure data lines again.
Do old and new comparison using the same strict and pedantic way.
This time concentrate to shape of high parts after a rising curve, like D4 and its lower noise parts and D0 and its repetition of changes.
For D6 check timing between later drop and earlier rising, and active shape after that drop.

And do it again from CPU pins if earlier measurement was from some other position.
Are they same or just similar?

If data measurement result is actually same all the time we can be sure that ROMs have something to do with measuring results.
Reasons can be many, but we must be sure, or it continues to be a wild goose chase.

asis:
Hi,

222Lab_Test222
Returned to reply #283 - very helpful.
-
All the diagrams I post are for informational purposes only, so they may contain errors and inaccuracies.
Keep this in mind.
There will be changes and adjustments.
-
Please take another picture of the back side of the DRAM FRAM modules, having removed the paper stickers beforehand.
Thank you.

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