exxos blog - random goings on

[exxos]

So something died on my H5 :(
:sigh:

With the RAM in the diag-cart shows RAM fault..

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If I plug the RAM in, I just get 1 odd square appear on the terminal and garbage on the screen ?!

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I swapped out the RAM, GLUE,MMU, CPU, poked around everywhere.. Just died out of the blue..

Anyone seen that kinda fault before ?

[PhilC]

@exxos ram buffer chip?

[exxos]

@exxos ram buffer chip?

Would it still spew out diagnostic information if the buffers were bad though..

I plugged in my little diagnostic board, it shows the correct binary sequence for the start of ROM. So it's not like the address or databus is completely trashed. It runs code from ROM , the diagnostic cartridge, but only when the simm is unplugged. I mean really the diagnostic cartridge shouldn't care if the RAM is bad :roll:

I just continuity checked the simm back to the MMU.. its fine . I did try a Falcon RAM card.. Same problems.. The last thing I did was solder a wire onto the ROM2 line. If the LS11 hd gone bad.. it would have still booted with a ST536 anyway.

I will have to try and find diagrom ST version somewhere and give that a go.

[exxos]

I'm not sure this helps either, thats just locked up at that point.

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I'm using this one..

https://github.com/terriblefire/diagrom ... gROMST.rom

104 space, and plugged into the H5 ROM socket.

[exxos]

Finally had a chance to have a look at this problem some more...

Got to address lines measuring 1.1K to Vcc which is wrong. The measuring between the two address lines there is a dead short ! The question is where.....

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I guess there is two options..

1) put my power supply across the two pins and see what start smoking..
2) go find my low resistance meter...

[exxos]

So option 1 it is..


Started with a gentle 10mA.

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Then 50mA.

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Then 300mA.

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Nothing got hot or smoked. Granted wattage not that high. But that's a pretty substantial short somewhere !


Time to bring out the low resistance meter then :roll:


So first of all testing across basically the middle area of those to address lines...

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Then measuring on the SMT GLUE pad.. Getting closer...

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Then measuring to the cartridge port.. Getting closer still...

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Cartridge port to the SMT GLUE pad.. Getting closer...

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Cartridge port to SMT MMU pad.. Getting closer...

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Cartridge port to the PLCC MMU.. Homing in....

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Practically right on top of it... !

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So looking around the ROM socket...

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:headbang:

#BobsLaw.

Now things are starting to happen ! :D

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[ijor]

So option 1 it is..
Started with a gentle 10mA.
...
Time to bring out the low resistance meter then :roll:
...
Cartridge port to the PLCC MMU.. Homing in....
...
So looking around the ROM socket...
...
Now things are starting to happen ! :D

See, I could never do that kind of hardware investigation, not even with the help of the most powerful AI in the world. At least not unless the AI can also control a robot to perform the actual physical work, not just give recommendations. :)

[exxos]

See, I could never do that kind of hardware investigation, not even with the help of the most powerful AI in the world. At least not unless the AI can also control a robot to perform the actual physical work, not just give recommendations. :)

Physical work like that its hard for me sometimes because of my RSI. My hands always been a bit shakey which doesn't help. I'm losing finer control in my hands which isn't good. Need to rest more.. Always so much to get done though which is the problem.

Will try and keep off the forum for the next few days. I've got some smaller projects I'm working on which I think are cool.

[exxos]

New toys :D

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[Badwolf]

New toys :D

Ooo!

BW