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Sony HitBit HB-F1 II – Power Supply Modifications

Whilst picking this up from a Hard-Off in DenDen Town, Osaka, I was told by the cashier that there was no power supply and that finding one would be a challenge. I wasn't too worried about this as using a 110v power supply in AU is just painful. Secondly, there seemed to be enough information on the internet to rig something together once I'd found time to do so back home.

So yeah, the power supply is a three-pin jack with AC 18v, DC 9v and Ground. This is confirmed on my unit by the voltage ratings inscribed on the base of the unit.

Finding an external supply with these two voltages would be an expensive task, so the better answer was to review the two links above to see what they did to convert. After a quick scan, it seemed that the AC voltage was used to create a -12v rail for the cartridge port and a +12v, which also was only for the cartridge port?. It seems that the MSX itself only needed the 9v DC, which it then also converted to 5v DC to run the entire system. Let's open'er'up! There are six screws under in the base that need removing. The lid will then lift off. The keyboard can then be removed, being gentle with the mylar ribbon cable.

You're then presented with the RF shielding. They've used a plastic-coated foil and it's quite soft! It's held down by screws around the bottom half, so find them all and remove them.

From here, it's the usual Sony-esque work of art. The PCB is so clean and tidy and the layout is precise. All the power paraphenalia is top-left and most of it will be redundant once we're finished with it. We're removing the power socket, so I went ahead and removed the motherboard from the case. There's 3 screws holding this down.

They went out of their way with the PCB graphic layer. They've actually drawn the connecting circuit lines on the underside of the board. There's no need to constantly flip it over if you're trying to trace a connection! There's also amazing information on pins of important ICs... and, for that note... DC sockets?

Seeing this written on the underside of the power plug threw me! Can I just supply the above voltages and get away with it? I won't need a complex supply for AC voltage if this is the case? I wired in the 12v line and, well, nothing came out! Hah. This seems to be a mis-print on the PCB? Those are NOT the voltages required.

So, I could go on about how I tested voltages in random locations and got some things going, whilst others stopped... and vice versa... but I wont, I'll just present the answer for this unit. You'll need a power supply that has +5v, +12v and -12v. Officially, you don't need the latter two if you're just using boring game cartridges. The unit only makes +12v and -12v to send to the cartridge port, and these are only used for "special" carts.. such as RS-232, etc.

Because I'm a perfectionist, I wanted to not 'downgrade' this machine... so I chose a Pico-ATX supply, as it had all the required supply voltages and an easy-to-use DC socket.

I de-soldered the ATX plug as it was just going to consume vital space inside the MSX.

On the MSX board, there's a large horizontal cable marked +/-12v. Desolder this from the left end and solder the appropriate wires to the associated supply voltages on the PicoATX.

Finally, there are two 7805 regulators that need to be removed. There's one that's bolted to the heatsink on the left and I de-soldered the wires from the mainboard. There's another nearby with a tiny heatsink on it that also needs to be removed.

With them both out, just flip the board and solder a wire into each of the OUT pins.

These need to be fed with 5v. I love how, even though the top regulator doesn't have the OUT pin described, that you can follow the traces easily from the IN of the lower regulator. The jumper wire, on the other side of the board, in the top-left of the image is drawn on this side of the board!

Once you've de-soldered the power socket, print out my personally-designed DC socket mount and use it to mount the DC socket to the board.

Finally, de-solder the power switch cable from both ends. Using one side of the power switch (it's DPST), connect one pin to ground and the other to PS_ON on the PicoATX.

Jam the lot back into the case.

When re-assembling, make sure to not screw the latches on the printer port. Try not to slice your fingers as you pinch them together and feed the board into the case.

Don't forget the two screws on the back of the case which hold the RCA socket and DC socket in place. These poor connectors get a lot of punishment. Before totally closing up this machine, I threw all the parts I removed into a zip-lock bag and stuck it under the lid. You never know, someone in the future might want to restore it to original condition?

And then it was done! Test? Of course...

Unfortunately, this unit doesn't have cursor keys! It's only got the gamepad directional arrows, and so I can't even play my favourite game.

Atari 7800 Controller Button Replacement

This Atari 7800 Gamepad came to me with one of the plastic buttons missing. They're held into the shell via two 2x2mm lugs and they must have perished after decades of abuse.

Without waiting around, I popped open the case and measured up the surviving button.

The button has a slight gradient on top, which I'm sure my 3D printer will struggle with...

And underneath there's a small tab to press on the rubber membrane inside the controller. Anyway, straight into Tinkercad I went to design a replacement.

I didn't even bother with the tab on the base... it's all just flat. The rubber membrane in the controller has a flat top anyway.

It printed OK! Could do with a sand, but I didn't have any wet-dry.

Not the prettiest... but it works perfectly! Here's the STL.