64K RAM board troubleshooting

[Witchy]

Hi folks,

After embarrassingly fixing my failing EXDOS problem earlier I now seem to have a dead 64K card in my hand-upgraded EP128. Zozo's RAM test in EXOS 2.3 detects 128K but fails it instantly which makes me think it's a 5V problem so I'll look at that later, but in the meanwhile is there a known fault with these boards? I've already reseated it.

Cheers

Witchy

[Zozosoft]

The most common failure are the broken wire somewhere.

[Zozosoft]

Try to view the failed memory in hex editor for example in ASMON. Then you can see if one or more data bits are non working (broken wire or dead RAM chip), or problem with address lines (99% broken wire).

[Witchy]

Hi Zozo,

Yes, I think the 5V wire for the 4164s is suspect since I resoldered it after removing/reseating the board and now there's various bits of RAM marked bad on power up so I'll reflow it again at some point

W

[Witchy]

Evening all,

I've remade the joint from the LS244 to the 5V line on the 4164s but getting the RAM test to hold without a keyboard connected is difficult. What's the preferred method of supporting the keyboard while still being able to get a DMM in to test voltages?

Cheers!

[Zozosoft]

You can use the keyboard membrane without the top of case.

[Witchy]

You can use the keyboard membrane without the top of case.

Hah! Why didn't I think of that

[Witchy]

Sweet, another one fixed. 2 broken wires that didn't become obvious until I took the board out to buzz it with a DMM

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[gflorez]

Aha!, you have an original RGB cable!

Can you put a picture of the connector?

[Witchy]

Sure!

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