NMS8280 recapping

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Door gianlucarenzi

Supporter (5)

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10-10-2020, 16:29

Hello, guys!
I am trying to revive back to life, my old NMS8280 MSX2 machine. It had some issue 30 years ago with the insertion of the front floppies, and at that time I stopped using it, due to the new Amiga 500 and Amiga 1200 machines. Sorry! ;-)
After almost 30 years of excellent storage I wish to power it on again. Firstly I dismounted it all, so I can recap it as soon as possbile, before turn it on again. I traced down ALL ELECTROLITICS capacitors (Video Board, Main Board and Power Supply) and they are a LOT!! Now I have a big list, but I do not know if it is good to replace them all. Are there any chance if there is a ready-made kit for it?
Regards,
Gianluca

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Van Meits

Scribe (6046)

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10-10-2020, 16:55

Hi and welcome.
Good to see you picked your 8280 up again.
I'm not aware of an existing capacitor kit. but if you invest perhaps a bit more than one hour you can probably create a list yourself.
Your computer is not on the suspect list. I personally would just switch it on.

Small tip: in the PSU set the jumper from 220V to 240V. The 4 diodes will love you for it.

Van jltursan

Prophet (2344)

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10-10-2020, 18:06

Quote:

Your computer is not on the suspect list. I personally would just switch it on.

Agreed, the NMS8280 (unlike the A1200) doesn't usually suffer of leaking or dying caps. Turn on the machine and only if you feel yourself brave enough, recap the machine.

Btw, welcome to the forum!

Van Grauw

Ascended (9396)

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10-10-2020, 19:30

I second the comments above. If the machine has no issues and no known problem with caps, recapping can do more harm than it does good (broken traces, placement errors, etc).

The thing you do want to watch out for with the Philips desktop models is that the front panel plastic is very brittle and can break easily when put under pressure, especially in shipping.

I generally have no hesitation turning on old MSX hardware. Of course stuff can break, I did have an issue with one logic IC that I needed to find and repair, but otherwise all my four MSX computers are in perfect health. And just blindly replacing all caps does not seem like something that would make them better in any way, but does create risk of messing up.

Also generally speaking I see more issues with dead RAM chips than capacitors pop up on the forums here. Yet there’s no general concept of “re-ramming”, and I think there’s no need for such a blunt axe approach. I think the concept of replacing all caps comes from and (only makes sense for) retro hardware communities where there have been known capacitor issues.

Van Pac

Guardian (5924)

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10-10-2020, 20:48

Don't forget to check the internal battery for a possible leaking. On the other hand, depending on the future application you have in mind, you might consider fixing the sound problems common in NMS8250/55/80 models. Here you have the service manual.

Van Meits

Scribe (6046)

afbeelding van Meits

10-10-2020, 21:03

The battery has probably gone below 1V, so it's useless now. The used battery is not known to leak because it's sealed.
Nevertheless cutting it out is the best way Smile

These come from 8250/5s which have been switched off for probably some twenty years and show no sign of leakage.

Van Alexey

Guardian (2896)

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12-10-2020, 18:01

Did anyone try to install the goldcap instead of a battery?

Van Meits

Scribe (6046)

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12-10-2020, 19:27

cr2032 with a diode to avoid recharging has been done.

Van gianlucarenzi

Supporter (5)

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01-11-2020, 20:16

Do you have a schematic to do so?

I suppose a diode in line within the Anode in the positive pin and the (K)athode in the positive of the CR2032 but this will prevent only a reverse fitting. And it will drop the voltage from 3.0V (CR2032) to a 2.6V to the computer. Is it correct anyway?

Regards,
Gianluca

Van gianlucarenzi

Supporter (5)

afbeelding van gianlucarenzi

01-11-2020, 20:19

Due to my job we usually use GOLDCAP for data retention of RTC. But it works for a couple of weeks without turn on the computer. It is worth the try only if you are planning to use the computer a couple days a week. Or one time within 15 days...

Van gianlucarenzi

Supporter (5)

afbeelding van gianlucarenzi

01-11-2020, 20:22

Thanks a lot for service manual. I will use it for sure... So my concern are about the powersupply big capacitors. The internal battery has 0.2V but luckly no leakage so far.

Thanks again

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