About NMS-8250 power supply

Master (195)

20-07-2009, 01:22

I've a question about NMS-8250 power supply: My computer has a third slot, so I'll use a Compact Flash and an old (very old) Zip-Drive into it (into the case), connected by an IDE interface. But I don't know if the original power supply will be able to provide energy for all these components (CF, Zip and a floppy drive). I'll be much easier to use it than installing a PC power supply into the case.
Any ideas?

Thanks in advance, Ricardo.

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Por Repair-Bas

Paragon (1176)

20-07-2009, 07:25

http://bas-ditta.info/verkoopenlinks/doehetzelf/8250voeding.htm

Por Bastiaan

Champion (333)

20-07-2009, 16:22

translation:
replace the 4 original diodes with a bigger type (6A), place them as high as possible to get a good (cooling) air-flow around them

Por RetroTechie

Paragon (1563)

23-07-2009, 02:52

Or:
* replace diodes with a >5A bridge rectifier, screwed directly to metal frame for cooling (easy/cheap), and/or
* replace +5V regulator with switching type, to make a much more efficient power supply (not so cheap/easy, but elegant fix).
Also check cooling on the +12V regulator if you're adding PC stuff like a ZIP drive.

Just out of curiosity: why use a ZIP drive, once you have a CompactFlash i/f attached? Aren't you making things more complicated than necessary that way

Por rjp

Master (195)

27-07-2009, 06:15

Thanks for all replies. I've got Zip-Drives (SCSI ones) in my Turbo-R and one of my Linuxboxes (my server). Besides that, I do have these Zip-Drives and some Zip-Disks. It's basically a way of "recycling" old stuff that can be still useful. I can't use a CD-ROM drive internally (lack of space).

Por rjp

Master (195)

27-07-2009, 07:04

BTW, my NMS-8250 was upgraded to a 2+, and it runs smoothly. But it has a ROM from a Brazilian "upgrade" kit. Although it has some funny issues, like having all portuguese accents in a keyboard which doesn't have them, I want to use the right ROM in my 8250.

Is there any specific ROM file for the 8250-based MSX 2+?

Por Erikie

Champion (324)

27-07-2009, 09:14

check this page: http://msx.retro8bits.com/msx-2-upgrades.html
there you can find roms for 8250 :)

Por rjp

Master (195)

07-08-2009, 01:01

Hi, I found the ROMs, but there was a problem: The SUBROM is a 64Kb (512 kbits) one, but the MSX can't handle more than 256 kbits SUBROMs. As I have been told, it would be necessary some form of mapping, which becomes more confusing. so, we tried some ROMs, but weren't successful.

Any ideas?

Por Erikie

Champion (324)

07-08-2009, 09:23

that is not true, in the 8250 there is no place for this you have to get an extra address line to the rom. It is all documented on HansO website. A15 needs to be connected to the rom with a wire from the mainboard. That pin should not be connected in the rom socket

Por rjp

Master (195)

07-08-2009, 17:57

I got these ROMs: http://msx.retro8bits.com/msxarchives/msx2plusromsjpnms8250.zip:

32768 Defl:N 26143 20% 08-30-03 13:19 4d0fa7b9 PLUSBIOS.ROM
65536 Defl:N 38286 42% 08-30-03 13:19 ef062f96 PLUSSUB2.ROM
32768 Defl:N 23509 28% 08-30-03 13:19 5818eee6 PLUSDISK.ROM

PLUSBIOS.ROM - NMS-8250's MSX 2+ Main ROM.
PLUSSUB2.ROM - NMS-8250's MSX 2+ SubROM.
PLUSDISK.ROM - NMS-8250's MSX 2+ Disk ROM.

Am I right?

So, why does it has 64 Kb?

We tried a MSX 1 ROM, and it runs perfectly. We tried some MSX 2+ ROMs (that one from above, and from the Brazilian upgrade kits AC88+ and DDX 2+), but none of them were successful. This MSX is a NMS-8250, which was upgraded to MSX 2+ (http://msx.retro8bits.com/msxdocs/v9958inNMS8250e.pdf), had a third slot (http://msx.retro8bits.com/msxdocs/philipsnms82xxslot3.pdf), and new colors (all silver). Ah, and I changed the power supply, from 220 to 110v, but I don't think it's really important.

We guess that there is some BIOS routine which is looking for something (maybe FM, or the RTC), and it fails.

Any ideas? Thanks in advance.

Por Erikie

Champion (324)

07-08-2009, 18:35

for 2+ you also need to build the F4 latch however the machine also boots without it but you will not see the MSX logo come up. And you cannot simply put the 64K rom chip in the 32K rom socket without taking care of A15 yourself
otherwise only 32K is visible and it wont work for you