Another conversation about the HB-F1 PSU

Por bartre

Supporter (6)

imagem de bartre

18-07-2021, 06:39

Heyo,

So I've spent the better part of two days of my free time digging into this, since I'm sick of having 1 good power supply for multiple systems.
I'm wondering how hard it would be to build up a new PSU for one of the compatible units.
I've read through the french posting for a new build here.

The circuit looks simple enough, and the info is out there to find the proper plug (sdd018-n1000/neo geo CD or I could swap the socket on the system)
But since I'm in an area where 120V is the standard, I'm wondering what it would take to adapt the existing design to handle a different voltage.

I'm pretty handy on fixing/soldering/etc, so i'm up to the physical task, but I'm not super familiar with the design/theory behind it.
Would I just need to find two transformers that deal in 100-120v and output the same as what's used in the french post?

If so, I've found these-
110 -> 9V
https://www.ebay.com/itm/153730704705?hash=item23cb106541:g:...

110 -> 18v
https://www.ebay.com/itm/153730704713?hash=item23cb106549:g:...

Also these on Newark

https://www.newark.com/block/fl4-18/isolation-transformer-4-...
https://www.newark.com/myrra/45031/isolation-transformer-10-...

total cost there would be about $25, then PCB, cord, diodes, and caps, but it's tough to find these on their own these days.

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Por bartre

Supporter (6)

imagem de bartre

18-07-2021, 08:06

I was drawing up what I'm thinking of, not a super complex circuit, but I just want to make sure I'm using the correct transformers.

Por gdx

Enlighted (4642)

imagem de gdx

18-07-2021, 09:06

Your schematic is bad for DC 9V. You have to do as indicated here:
https://www.msx.org/forum/msx-talk/hardware/panasonic-fsaa51...

Also check out the FS-A1 and HB-F1 wikis.

Por bartre

Supporter (6)

imagem de bartre

18-07-2021, 15:36

Thanks, I had read through that topic but I guess I hadn't completely grasped it.
The 9v transformer I linked is listed as 2X9v, which should be adequate for the schematic listed in that thread.

so a crude redo-

Por gdx

Enlighted (4642)

imagem de gdx

18-07-2021, 16:26

The capacitor must be after the diodes otherwise you will have a short circuit.
There is no fuse in the original power supply. They are not very useful but if you want to put, calculate the right values. There are not the same intensities. Also, put the ~9V GND in the center of the two coils.

Por Pentarou

Champion (389)

imagem de Pentarou

18-07-2021, 16:35

Given that nowadays there are cheap and good UBEC modules, wouldn't it be cheaper and more space efficient to use only the 18v AC transformer and replace the whole 9v section with a 9V UBEC (or similar DC-DC converter)?

Por gdx

Enlighted (4642)

imagem de gdx

18-07-2021, 17:03

With an oscilloscope you get a 9V signal about as follows. (dotted signal is without the capacitor)

Pentarou wrote:

Given that nowadays there are cheap and good UBEC modules, wouldn't it be cheaper and more space efficient to use only the 18v AC transformer and replace the whole 9v section with a 9V UBEC (or similar DC-DC converter)?

The goal is to make a power supply similar to the original without modifying the MSX, but otherwise, you can take directly a power supply -/+12V and + 5V, or only +12V and then recreate the -12V (with a voltage inverter) and the +5V (with a regulator circuit) from +12V. There are several possible solutions.

Por Pentarou

Champion (389)

imagem de Pentarou

18-07-2021, 17:08

Yes, it's obvious that the whole MSX can be powered by just one voltage, but I was talking about the 9V DC section inside the HB-F1 PSU.
The design from msxvillage is an exact replica of the original but there's no need to do that.
Instead of 2 different transformers, one can use just one (for the AC) and use an UBEC to generate the DC.
As I wrote above it would be both cheaper and more space efficient.

Por bartre

Supporter (6)

imagem de bartre

18-07-2021, 18:55

gdx wrote:

The goal is to make a power supply similar to the original without modifying the MSX, but otherwise, you can take directly a power supply -/+12V and + 5V, or only +12V and then recreate the -12V (with a voltage inverter) and the +5V (with a regulator circuit) from +12V. There are several possible solutions.

I was not aware of this.
So these models can be powered off of lower voltages than indicated on the PSU?

Regarding the UBEC suggestion, if I'm understanding correctly, this would essentially break down to running the one transformer to get the 18VAC, then in addition to running that to the system, also use the transfomer to power the UBEC which would handle the output of the 9VDC?

using one of these or similar I'm guessing?
https://www.getfpv.com/ubec-high-voltage-adjustable-6v-9v-12...

Por Pentarou

Champion (389)

imagem de Pentarou

18-07-2021, 19:29

Most MSX computers use 5V DC for the logic chips and +/- 12V DC for the audio/video circuits or add-on cartridges.
The external power blocks are rated higher because the voltage conversion happens internally to the computer (also older linear adapters needed a bit more voltage than they output) .

So in most cases it's possible to use a single 5V PSU coupled with a small adapter board like this one +5V Input & 12V Positive/Negative Dual Output (used by the Omega MSX).

Quote:

running the one transformer to get the 18VAC, then in addition to running that to the system, also use the transfomer to power the UBEC which would handle the output of the 9VDC?

Yes.

Por gdx

Enlighted (4642)

imagem de gdx

19-07-2021, 10:30

I think you can just take one transformer with two AC 9V outputs (about 24VA) and get AC 18V with 2 x 9V in serie and make the DC 9V as indicated in the diagram above.

Pentarou wrote:

As I wrote above it would be both cheaper and more space efficient.

Not sure.

I think you can use a pico PSU but it requires modifications of the MSX.
https://www.ebay.com/itm/352971291251