Beware usb 5v mods for japanese MSXs

Par pakoto

Resident (38)

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03-02-2022, 10:37

Some mods has been published, and jap msx modified with 5v usb mod are being sold.

They work perfectly with original cartridges and floppy adapter, but any DIY cartridge (sound cartridge, sd mapper, sdmmr...) or orignal music carts needs +12v or even -12v.

Keep that in mind when buying or selling those msx. Only if support +5v, +12v and -12v are fully compatible.

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Par pakoto

Resident (38)

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03-02-2022, 13:24

EDIT: SDMMR don´t need +-12v, works with only 5v.

Par ducasp

Hero (550)

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03-02-2022, 15:21

Technobytes 9990 and OPL4, at least the Konami style/size ones, do not use 12V or -12V at all, I remember this from when I was helping Victor Trucco to debug the prototypes of SM-X and I have those cartridges and 12V and -12V are not connected at all....

Schematics of SD Mapper also do not show usage of anything other than 5V:

https://github.com/fbelavenuto/msxsdmapperv2/blob/master/Har...

Not that I'm a fan of those mods, just making it clear about stuff that doesn't depend on +/- 12V

Par pakoto

Resident (38)

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03-02-2022, 17:05

correct, thanks. Can´t edit first post.
Now i have an sdmmr full working with modified sony jap msx2, only with 5v line connected.

curiously, two msx1 i try to replace power supply don´t boot only with 5v. Euro sanyo needs +12v to boot up. National japanese msx1 need same 5v/12v to boot, but also needs -12v to get clear sound.

Par Grauw

Ascended (10581)

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03-02-2022, 17:30

The Panasoft FM-PAC requires 12V afaik.

Par Alexey

Guardian (3385)

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03-02-2022, 19:53

Carnivore2 requires both 12v power inputs for the amplifier.

Par Parn

Paladin (784)

Portrait de Parn

04-02-2022, 17:22

Please forgive my ignorance, but what is a USB 5V mod? I've looked around but I can't make head or tails of what I found.

Par Grauw

Ascended (10581)

Portrait de Grauw

04-02-2022, 18:14

I presume it is replacing the power cord or power input connection with an USB B-type connector. Useful for machines where the internal PSU has failed (difficult to find a fitting replacement) or where the external PSU is missing and the connector is an unusual one (looking at you, FS-A1).

This is the first time I’ve heard of it, I guess it is a creative solution, though not without issues.

Par Briqunullus

Champion (512)

Portrait de Briqunullus

04-02-2022, 18:14

I was asking myself the same question. Maybe it's this one? Although that one seems to have a DC-DC converter for +-12v.

Par raulsantacruz

Hero (600)

Portrait de raulsantacruz

05-03-2022, 20:55

Briqunullus wrote:

I was asking myself the same question. Maybe it's this one? Although that one seems to have a DC-DC converter for +-12v.

Exactly! I have one computer converted using this mod and 12+ cartridge works perfectly (tested with FMPac , V9990, etc.).