NMS8245 Troubleshooting Tips

By luppie

Paladin (854)

luppie's picture

12-04-2014, 10:58

I'm in the process of restoring a 8245
Now I've got an extra 8245 that is not working and before I'm using that one for spare parts, I want to try to get this machine back2life. When I power up the machine I've got a black screen and my OSD tells me that there is a NTSC signal.
(Randomly the internal relay gives me the click of death, but most often there is no click)

On the slot's I've got a +12V / -12V / 5V (it's 4.99554 V)

After optically inspecting all electronics I found that R26 on the Pal-Encoder was fried and replaced it. No Luck.
I swapped the Pal Encoder with my working machine and the Pal encoder works in the other machine, but not in the defect machine.

The machine was upgraded with 7Mhz, so it was easy to replace the CPU with an other one and revert the 7Mhz Mod. Still no luck.

The main rom was also on a socket so I've tested that one also in the other machine, the Rom works normaly.

I removed the Ram IC's and tested the machine with a external memory mapper, still no luck.

There are no other components anymore that I can easily swap between the 2 machines, so I'm looking for other things I can check/measure. Looking at the datasheet I can only find repair/troubleshoot instructions on the drive and not on the machine it self. Any hints on how to troubleshoot this any further ?

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By luppie

Paladin (854)

luppie's picture

14-04-2014, 21:33

Tonight I have replaced the VDP and now I'm getting randomly a White or Black or Red or Green or Yellow or Blue screen or less often a click of death.

Still looking for other options to get this machine back to life.

By Denus

Expert (120)

Denus's picture

20-04-2014, 12:18

Ok I know, it's obvious, but I guess the easiest way is to buy a cheap beaten-up but working third system.

That's what I did with my Toshiba HX-10: got 3 of them and could restore two machines.
One is now pristine (very pleased with it), another is also good looking and working great and the third one has now all the broken and defective casing, KB and electronics parts and is only meant for some spare parts, if required.

Although the NMS8245 is quite hard to find these days.

By Daemos

Paragon (1669)

Daemos's picture

20-04-2014, 15:37

Quote:

Tonight I have replaced the VDP and now I'm getting randomly a White or Black or Red or Green or Yellow or Blue screen or less often a click of death.

This means something has changed but the problem is not solved. Sounds like a power surge to me. Propably the device had a bad voltage overload so many chips might have been damaged. I don't know how to test for bad digital parts though... FInding out if the S3527 is still allright is a good start. It will save you a lot of trouble and headaches since that one is non replacable.

By Eugeny_Brychkov

Paragon (1066)

Eugeny_Brychkov's picture

20-04-2014, 23:58

luppie wrote:

Still looking for other options to get this machine back to life.

Needs troubleshooting. Which diagnostic tools do you have?

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