Toshiba HX-10 no power

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By BignellaMSX

Resident (42)

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26-04-2021, 12:42

Hi all,

I recently dug out my MSX collection from my parents loft, I thought they'd thrown it away, so well happy to find it!

Trouble is the power light doesn't come on.
I've seen some posts where the power works but black screen but nothing about restoring/checking power supply.

Any pointers? I have no idea where to start.
I would really like to get it working and play from my carts rather than emulators as I have for many years.

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By Alexey

Guardian (3239)

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26-04-2021, 19:34

Usual thing - open up, check visually for broken or burnt components first. Then check what's on +12v, -12v and +5v power rails with a multimeter. If one or more voltages are missing, check what's coming to voltage regulators' INPUT pins. I case of a missing voltage on the input, check the diodes that convert AC to DC. If the problem is still not localized, it's worth to check what's coming to the board from the transformer (AC).

By BananaPie

Resident (58)

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28-04-2021, 20:45

I had to do this on another MSX machine. Without a multimeter, you can't do anything.

By BignellaMSX

Resident (42)

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29-04-2021, 09:37

Ok, I've got a multimeter and there's power from the transformer connector.

Only one chip looks a bit dodgy:

I'm going to attempt to check voltages on the board.

By BananaPie

Resident (58)

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29-04-2021, 10:51

Do you have any contact cleaner? Make sure the pins are not bent.

By Jipe

Paragon (1515)

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29-04-2021, 10:53

this is the VDP video processor with oxidized silver pins

clean with white vinegar and rub with a toothbrush

By BignellaMSX

Resident (42)

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29-04-2021, 13:18

oh, ok, so not burnt out.

everything else has gleaming silver pins so this one stood out.
the actual end of the pins that go in the socket are all clean and silver.

By BananaPie

Resident (58)

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30-04-2021, 12:53

Make sure that the PSU is getting the correct power from the external plug once more before you close the machine.

By BignellaMSX

Resident (42)

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30-04-2021, 16:27

Completely dismantled it for a good clean and it looks like there may have been a spillage at some point. Not that I remember it, but wouldn't put it past my younger brother to have done it and not told anyone!

But the marks are only on the bottom plastic and the large metal base plate bottom, there's no evidence of it on the PCB.

PCB looks fine

The only other dodgy looking thing I've noticed is the solder around these pins

I've tested continuity across the board and that's fine. I just can't seem to get a voltage anywhere other than from the PSU connector although having not used a multimeter before I'm relying on what I'm reading on the web.

If anyone is able to actually show me where I should be placing the testing probes for the different voltages that would really help. I've looked at the diagram on the back of the board but that doesn't really help.

By Alexey

Guardian (3239)

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30-04-2021, 16:53

Please make a picture from the component side of the board.

By Jipe

Paragon (1515)

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30-04-2021, 17:11

with a multimeter on the connector SLOT #1 you can verify :

+5V between pin 41 45
+12V between pin 41 48
-12V between pin 41 50

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