Broken ON/OFF switch

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By CX5Mer

Champion (327)

CX5Mer's picture

11-07-2015, 15:27

Unfortunately the ON/OFF switch on my Philips VG-8235 MSX2 has now broken down completely! This switch has never worked 100% of the time ever since I got this computer last December, which was always worrying me, but at least I can be sure that it's the switch itself which isn't working, instead of any of the many other components. Some of you are probably thinking now that this is a simple repair job. Unfortunately, I don't know how to repair it. Please can you give me some instructions on how to do this repair?

BTW, I've had a look at the service manual on http://msx.hansotten.com/uploads/msxdocs/vg8235sm20.pdf and it means nothing to me! I hope someone can explain how to do the repair in a way that I can understand.

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By Jipe

Paragon (1594)

Jipe's picture

11-07-2015, 15:57

exist two supply power in Philips VG8235
check the model under the MSX
/00 , /19 ,/39 or other type

By CX5Mer

Champion (327)

CX5Mer's picture

11-07-2015, 16:06

It says on the label underneath "TYPE VG8235/00 220V 50Hz 24W". I haven't yet unscrewed the case and I'll wait until after I get some instructions from someone before I do this.

By Jipe

Paragon (1594)

Jipe's picture

11-07-2015, 17:39

this is a integrated power supply and the switch is inside a metal box

see : http://img543.imageshack.us/img543/9448/dsc01012.png

By CX5Mer

Champion (327)

CX5Mer's picture

12-07-2015, 11:20

How can I repair it then? The metal box probably contains capacitors which could kill me if I touch them. I don't want to have to pay postage from the UK to the Netherlands and back again to get it repaired. The PSU looks a bit like a PC PSU, but must be smaller.

By Jipe

Paragon (1594)

Jipe's picture

12-07-2015, 13:08

yes is dangerous if the supply is broken , the capacitors can contain 400V
don't connect to 220V
you can let wait two day for discharge capacitor
normaly open the cover and don't touch the board for acces to the switch
you can shunt the switch for trying the power supply
but closed the metal box before testing
-
warning to 220V , if you are not sure don't make it

By RetroTechie

Paragon (1563)

RetroTechie's picture

13-07-2015, 03:55

You need a dual-pole, single-throw switch, that's specified for 230V AC use, and fits in the available space with enough clearance for electrical safety. That is, with 2 "make" contacts that operate in parallel. Any electronics and some hardware stores will have something usable (if you can't rip something from an old VCR in your attic LOL! ). If there's an electronics store near you, just bring the switch or opened psu with you. In the ideal case, something that fits in there 1:1. If not, something that will require a bit of drilling / grinding the metal box to make the switch fit (if necessary in a different location). If all else fails, you could route AC wires out of that box & fit the switch elsewhere in the computer case.

Jipe wrote:

the capacitors can contain 400V

Ehm, ~320V (DC).

Quote:

don't connect to 220V
you can let wait two day for discharge capacitor

Ehm, under a minute (see schematic, there's bleeder resistors across "bad boys" C4/C5). There may be a few other capacitors that retain charge after power off, but not with enough energy contents to do damage (to a person).

CX5Mer wrote:

Some of you are probably thinking now that this is a simple repair job.

It is, period. Does not require instructions, schematic, or component specifications. Unless...

Quote:

Unfortunately, I don't know how to repair it.

That alone suggests it may be better to have someone else do it. Finding a suitable switch is easy, wiring it up too. Doing that in a manner that's reliable and SAFE both mechanically and electrically, is not hard either but requires some experience.

Are you sure you want to do this yourself? Unless you're living in the middle of nowhere, I have no doubt whatsoever that someone who knows how to fix this properly, will live within a few hundred meters from you. FIND THAT PERSON! (rather than botch it and put yours or other people's lives at risk).

By CX5Mer

Champion (327)

CX5Mer's picture

14-07-2015, 18:56

Thanks for your advice RetroTechnie! To sum up, I need a dual pole, single throw switch, which fits into the space.

I don't know anyone local who could repair it. There are basically two things I could do.

1. Take the switch and my Philips MSX2 computer along to a Restart Party as on http://therestartproject.org/events/

2. Contact the eBay seller, who I found out is a member of a well known MSX club in the Netherlands. This club has probably got a spare compatible PSU which they could send me.

BTW, I'm confused about the mentions of a 230V PSU. This Dutch MSX2 computer dates from the time when the Netherlands used 220V and the UK used 240V. Even so, it was possible to use 240V appliances on 220V and probably vice versa as well.

By NYYRIKKI

Enlighted (6016)

NYYRIKKI's picture

14-07-2015, 20:03

If you can't find replacement, one option is just to remove/skip the switch and glue this to backplane.

By CX5Mer

Champion (327)

CX5Mer's picture

14-07-2015, 21:22

That looks good. The problem is how to remove/skip the switch.

By CX5Mer

Champion (327)

CX5Mer's picture

14-07-2015, 23:41

I have just managed to take the case apart so I can look at the PSU and the other parts. What I found was a PSU which is marked 230V instead of 220V or 240V, but it doesn't seem to be completely enclosed, unlike a modern PC PSU. There's a gap where someone could stick their fingers right into the PSU, with some fairly large capacitors to the right of this. Another issue is that I'm not sure where this PSU ends. There's a circuit board to the right which is partly on top of the PSU and prevents me from removing the metal semi enclosure unless I also unscrew that board. There seem to be connectors coming from the PSU plugged into two places on the motherboard. One on the left edge, which looks similar to a PC Molex connector, and another on the right hand side of the motherboard, which may be the main power connector to the board and is definitely smaller than a 20 or 24 pin PC PSU connector. I wasn't really surprised to see that some repairs have been done with wires connecting different parts of the motherboard, which I assume are because of broken tracks on the motherboard. I've taken some pics of all this, which I hope to post on here soon. Obviously, I haven't managed to get access to the part of the switch inside the PSU yet.

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