Power supply for Philips VG-8010 MSX

Guardian (3597)

26-05-2019, 21:50

DISCLAIMER: THIS INFORMATION IS FOR EDUCATIONAL PURPOSES ONLY. I AM NOT RESPONSIBLE FOR ANY DAMAGES RESULTED FROM SIMILAR MODIFICATIONS TO ANY MSX COMPUTERS.

Recently I've got a Philips VG-8010 MSX computer without a power supply. The machine was sold as "broken", but after connecting +5v to the board it booted normally. I tried to find a matching power supply for it, but didn't succeed. Also the connector of the PSU on that computer was non-standard, so I decided to check if it was possible to install an internal power supply. Luckily this machine has an RF module that is completely useless nowadays. So I removed the module and its cable and measured the amount of free space inside. According to my calculations the remaining space should have been enough for a 30 Watt triple voltage power supply like this one:

https://www.aliexpress.com/item/Factory-outlet-30W-5V-12V-12...

For the total price of 11.5 Euro the experiment would be OK even with a failed result. So I bought that power supply from AliExpress. It arrived yesterday and I started the modification. First of all I removed the shielding and heat dissipation plate from the PSU. I placed the power supply inside and noticed that a small modification was necessary for the bottom of the case. I removed around 1cm of plastic so that the remaining heat dissipation plate could fit inside (see the red arrow):

As this PSU gets quite hot, I drilled a few 3mm holes near the heat sinks:

Those holes should improve the ventilation of the case when the power supply gets hot. The RF socket's hole offered a nice opportunity to get the 220v cable into the case. So I took a standard PC power supply cable, cut the connector and glued it into the case while leaving the wires ready for connecting to the PSU:

The PSU without the shielding and the heat dissipation plate looks like that:

As the PSU is going to be installed upside down, its board needs some protection to avoid touching the aluminum plate that the keyboard is mounted on. So I cut a piece of thick transparent plastic (some PC PSUs have those under the board) and glued it onto the board:

Then I took a few thick wires from a busted PC power supply: 2 red wires for +5v, 2 black wires for ground, 1 yellow wire for +12v and one orange wire for -12v and connected everything including the 220v wires to the PSU:

A few cuts in the transparent shielding were necessary for the upper case cover to get properly closed (see the red arrows):

To fit properly the remaining heat sink needed to be a bit trimmed (see the red arrows). Also as the heat sink gets mighty hot, I had to install an additional heat dissipation plate made out of 1mm thick aluminum stripe that I used to create a holder for FS-A1ST's 220v transformer before. I cut the long enough piece, drilled 2 holes and attached the stripe to the main heat sink with 2 screws that used to hold the original heat dissipation plate. I also put some thermal paste between the stripe and the heat sink:

Then the wires were soldered onto the board. I soldered the ground wires to 2 different places on the board. The power wires were soldered to the tracks near the power socket. After some cable management it was time to close the upper case cover:

It closed without any major effort, but required a bit of a push. The screws secured it well. Now I am running a test with King's Valley 2 and Carnivore (1 hour so far) to make sure that the power supply inside doesn't overheat. It gets hot, but not more that 80 Celsius. Will run it for a few more hours:

Maybe someone will find this information useful.

Por Manuel

Ascended (19465)

26-05-2019, 21:59

Wow, impressive, but it sounds rather risky and invasive... and 80 degrees sounds really really hot! Why is it getting so hot??

Por Wierzbowsky

Guardian (3597)

26-05-2019, 22:25

Actually I only estimate the temperature to be 80 Celsius inside. It's probably lower, but I can't measure it with my tools. Without the upper case it was around 56 Celsius under the same load. I don't think that even 80 Celsius could damage the PSU. It may reduce the lifespan of the voltage converter (or whatever part) that is attached to the heatsink, but I am ready to take this risk.

Normally the heatsink is attached to the massive aluminum plate that serves the base for the PSU board. And the metal shielding that is attached to the plate also helps to dissipate the heat. Without these parts, the PSU's remaining heatsink gets VERY hot under load. So without the additional home-made heatsink that I attached myself, using the PSU inside the MSX would be quite risky.

Por gdx

Enlighted (6213)

27-05-2019, 02:45

Good job Alexey!

Original power supply provides three DC voltages (+5V, +12V, -12V). MSX1 without floppy disk drive rarely consumes more than 25W. Your power supply can provide up to 30W. So I do not think it heats so much, probably about 60°C maximum.

It's less convenient but me, I would have kept the shielding and I use it in a external case.

Edit: On MSX the majority of the current goes through the 5V but maybe your power supply has been thought for a consumption spread over the three voltage. That would explain why it heats a lot.

Por Wierzbowsky

Guardian (3597)

27-05-2019, 12:32

I had a thought about making an external case. But then I would need to change the power socket and that looked like trouble. So I decided to go for the internal solution and it worked out well. A few hours of testing with Carnivore2 playing several games didn't reveal any problems.

There's minor interference on the composite video, probably from the unshielded PSU, but that is bearable. On RGB there should be no artifacts. I will make the RGB cable soon and test it with my GBS-8200 converter.

Por Wierzbowsky

Guardian (3597)

27-05-2019, 21:30

WTF? This computer doesn't have RGB out? What a PoS design...

Por Grauw

Ascended (10768)

27-05-2019, 21:45

Unlike the V99x8, the TMS9918 doesn’t output RGB natively does it? Most MSX1 computers don’t have RGB output I think. But then for some reason the French models do, for some reason.

Por The_Engineer

Master (192)

27-05-2019, 22:15

Quote:

But then for some reason the French models do, for some reason.

Well, SECAM and SCART are responsible for that.

Por gdx

Enlighted (6213)

28-05-2019, 01:58

You must replace the TMS9918/9118 with TMS9928/9128 and do some modifications to make output RGB natively.

Por RetroTechie

Paragon (1563)

28-05-2019, 06:37

Grauw wrote:

Unlike the V99x8, the TMS9918 doesn’t output RGB natively does it?

Wikipedia has a nice overview. The ones marked "luminance and color difference" output Y, B-Y and R-Y signals, which is relatively easy to encode into RGB. Basically using a transistor circuit to add/subtract some signals. It's similar (but not the same I think) as YUV signals.

Iirc the 99xx types use 16K x 1 bit VRAM (the infamous 4116 chips), the 91xx type can use 16K x 4 bit chips. Toshiba's T6950 outputs composite video (NTSC/PAL switchable).

Quote:

Most MSX1 computers don’t have RGB output I think. But then for some reason the French models do, for some reason.

Noticed that too. I suspect the SCART connector has been quite popular in France, hence much gear released over there made sure to include RGB output.

@Alexey: nice opportunity to contribute to the power consumption thread ;-)

Por zPasi

Champion (499)

30-05-2019, 10:09

Nice project! I have one VG-8010 too, so this looks interesting.

I wonder, in theory a RasPI capable 2.4A USB power supply should be more than enough for an MSX. Of course there is no +-12V but you can generate that with a dual-voltage DC/DC step-up converter module like this one.

Worth a try?