nms 8245 joystick port failure ?

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Por GreyFoxNL

Rookie (23)

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24-11-2018, 22:43

GreyFoxNL happy is an understatement Omega. Both the 8245 and 8250 in perfect working order now.
It's a shame i have to work tomorrow Big smile. Thank you so much for your time !!!!
I would also like to thank everyone that posted here in this thread, it was all very helpfull in the process of getting my 8245 fixed !!

Off topic: my megaflashrom arrived while you were fixing my computers omega Big smile...
Lets get it installed and hope i will get some sleep tonight .....

Por Omega

Master (231)

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25-11-2018, 02:27

No problem, happy to have saved two more MSXes Smile
Have fun with them and your MFR!

Por gdx

Enlighted (5575)

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25-11-2018, 09:56

Great!

Where did you find these S3527?

Por GreyFoxNL

Rookie (23)

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25-11-2018, 17:09

Lucky for me, Omega had a donor board from a 8245 lying around.
Talk about a needle in a haystack Smile

Por Louthrax

Prophet (2414)

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25-11-2018, 19:11

Nice story, and nice soldering skills! Replacing a whole MSX engine is something that would still make me a bit shaky Smile

I'm also wondering what could cause these MSX Engine chips to break (as this seems to be a common issue)? Only aging or something bad from the user side ?

Por GreyFoxNL

Rookie (23)

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25-11-2018, 19:20

My guess is that something happened during transport in this case.
I trust the seller and he tested it before it was shipped.

Por Manuel

Ascended (18845)

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25-11-2018, 20:39

I heard once from Bas that a short-circuit at the joystick port can cause this. I've had the same issue once. So, perhaps you did it yourself when plugging something in or touch it with something.

Por GreyFoxNL

Rookie (23)

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25-11-2018, 22:50

straight out of the box it had the mallfunction and i didn't use a joystick when the error occured.
Guess we will never know for sure what caused it... the most important thing is that a very good looking nms8245 has been saved and is ready for many more years of service Wink

Por Omega

Master (231)

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26-11-2018, 21:30

On this model the joystick ports are directly connected to the engine. So if you for example have a static discharge while your fingers touch the joyports, it will most probably kill or damage the engine Sad

Unfortunately most MSX models have directly connected stuff like parallel port and joysticks. Manufacturers could have put buffers in between for protection, but that would have increased cost price... The LF devices Philips used are just noise suppression, they don't protect the inside against voltage discharges. Another likely cause for damaging such an input is connecting some device that isn't supposed to be connected to the MSX.

A simple short circuit isn't likely to cause issues to such a port since that is what a joystick does: shorting the input to gnd. Shorting it to +5v would not matter, it would just read off..

Replacing the Engine isn't that difficult if you have the right equipment: a hot air station, some SMD soldering skills and good flux. A hot air station can be bought for 50 bucks (858D clone from China). Hot air is used for desoldering, for soldering in a new component any decent soldering iron will do (preferably temperature controlled). In any case: do not practice smd soldering on a MSX board Eek! Take some old internet router or something like that and use it for practicing de/resoldering smd Wink

Por Manuel

Ascended (18845)

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26-11-2018, 23:43

Omega, thanks, that's what I meant. Discharges, not short-circuits Smile

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