Need help repairing Philips MSX2 NMS 8250

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By llopis

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17-09-2019, 21:40

New update in the saga. Unless some new revelation come up, I'm ready to throw the towel.

A friend of mine has an 8250 that was working years ago. So I thought it would be very useful to have a working one side by side to compare what's going on and potentially replace ICs. Great.

I get it, fire it up and... black screen and light on the keyboard always on, just like my faulty one! Weird, but just about anything can cause that. I open it up, start looking around: voltages fine, clock signals fine, data lines fine... /CAS on the system RAM, always high. Just like mine!!!!

So what's going on? Is there some magic to make these computers work and I need to do something more than just pressing the POWER button?? Or are these computers designed in such a way that when anything fails, they always end up having the same symptoms?

By Manuel

Ascended (15696)

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17-09-2019, 22:21

The common thing is... you! What did you do to these poor innocent machines??? Tongue

By llopis

Rookie (32)

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17-09-2019, 22:40

Seriously! I even started wondering whether I had to had the keyboard plugged in for example since for most tests I had it unplugged. But no, that wasn't it.

By Manuel

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17-09-2019, 23:29

So did you try to replace the VDP?

By llopis

Rookie (32)

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18-09-2019, 08:33

No, I didn't. I would have swapped it with this one from my friend's, but since it also wasn't working, I figured I wouldn't get very far.

By llopis

Rookie (32)

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18-09-2019, 09:36

Oh, and just to make sure I'm not being a total idiot, I did try the composite out and the RF out with the same results. So it's not just a matter of my SCART cable being bad :-)

By Manuel

Ascended (15696)

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18-09-2019, 10:43

Sure, but your lit up CAPS lock LED indicates something is wrong other than a video cable...

By llopis

Rookie (32)

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18-09-2019, 12:20

Actually, there is something in common between the two MSX2s: the keyboard. My friend just gave me the main unit to test figuring I already had a keyboard. Maybe I have a killer keyboard from hell :-)

By Grauw

Ascended (8398)

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18-09-2019, 12:37

So does it boot up with the keyboard disconnected?

By llopis

Rookie (32)

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19-09-2019, 10:20

Grauw wrote:

So does it boot up with the keyboard disconnected?

Nope. Doesn't boot with or without it.

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