USB power mod

By dproldan

Rookie (19)

Аватар пользователя dproldan

12-12-2021, 17:55

Hi.

These last weeks, I've been repairing and restoring some computers that had no power supply. Instead of tracking down and buying the hard-to-find power supplies, I decided to use USB power adapters to get 5VDC and use a DC-DC converter to get the +-12 volts needed for some parts of these computers and for the cartridge slots.

The only goal of this modification is to have these otherwise wasted computers back in working order, no more and no less. It has been tested thoroughly with all kind of cartridges and combinations without any issue, so that goal has been reached. If you want to replicate this, keep reading!, but I will not be responsible for anything that happens to you, your computers or your property. I'm only showing what I did but I don't recommend you do it.

The parts used are:
- USB B female connector.
- 5 v input, dual +-12 v output, 2W DC-DC converter: (RKZE-0512D, DPUN02L-12, PDM2-S5-D12-S or equivalent)
- 6 cm pieces of wire (2 x black, 1 x red, 1 x yellow, 1 x blue)
- epoxy glue

This modification has been done to the following computers so far. It could work with may others, but the pictures and instructions are for these:
- Panasonic FS-A1
- Sony HB-F1
- Sony HB-F1II

The summary of it is:
1.- Remove the original power input connector and the voltage regulator
2.- Place the USB connector on the PCB and connect the 5 volts rail
3.- Place the DC-DC converter and solder the cables to the PCB

Let's start! (all pictures are here too: https://imgur.com/a/C8tVDBh)

1.- Open the computer and desolder the Power input connector and the voltage regulators:

2.- Check the USB connector placement, mark the holes, make the holes:




3.- Solder the cables to the USB connector and the DC-DC converter, important!! use heatshrink tube or hot melt glue to protect them, you don't want a loose wire inside the computer:

4.- Solder the USB connector and the 5VDC input (sorry I only have one picture of the Sony computers, GND should be clear, 5 VDC is always the center pin of the original connector) :

5.- Attach the DC-DC converter to the PCB with epoxy or something strong. Don't cover any holes in the PCB!

6.- Solder the wires as shown:

Sony HB-F1 II:

Sony HB-F1:

Panasonic FS-A1:

7.- Make a bridge from input to output of the original 5 VDC regulators.

Sony HB-F1:

Panasonic FS-A1:

8.- Check everything is correctly placed, no short circuits anywhere, and... try it!

You should use a 1 amp USB adapter and a good USB printer cable. There are some thin cables that will cause problems.
Also, some USB B male connectors are too short to work. Use the long ones:

Enjoy!

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By raulsantacruz

Hero (600)

Аватар пользователя raulsantacruz

12-12-2021, 18:43

Incredible mod Daniel!!! Nishi Nishi Nishi I can confirm they works like a charm!!

Thank you for share with all

By Pentarou

Champion (423)

Аватар пользователя Pentarou

12-12-2021, 18:54

I saw the pictures elsewhere and I agree that the finished mod looks very clean, however...
Normal USB will give only 100mA unless you trick it by joining the two D signals (if I remember correctly) and in any case, even if you are using a dumb PSU that gives max current regardless of the device, you will only get 1.8A max.
Cheap cables will also give a massive voltage drop, did you measure if you are really getting 5V or something like 4?

By Alexey

Guardian (3375)

Аватар пользователя Alexey

12-12-2021, 19:32

From my own experience with USB cables I can tell that quite a few of them contain very thin wires that are not capable of carrying more than few hundred mA current. So, even if you are going to use a 2A rated charger, with USB2 cable you won't get enough current at the machine.

If you are going to power up an MSX that normally needs 2-3A current (and if it has an old disk drive, then the peak values can be even higher), you have to use USB3 cables that are designed to carry up to 2A. And the sockets should be also USB3 compatible.

In addition, if you are using DC-DC converters, you should put 10uF filter caps for inputs and outputs.

By Pentarou

Champion (423)

Аватар пользователя Pentarou

12-12-2021, 19:37

IMHO USB3 cables and sockets are a bad idea: expensive and difficult to find.
USB C is a better solution. As it has become the standard to power small devices.