nms 8280 & v9958?

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Por grit

Resident (53)

imagem de grit

24-10-2007, 18:51

I've started this conversion a very long time ago. Also built in a SIMM memory expansion and then my 8280 did not boot. (I only heard the cassette relay click and that was it.) I've taken out the simm expansion already, managed to find some 64K x 4 memory bank chips to restore that to original but I would like to keep the v9958 inthere.

Has anyone on the forum here done the V9958 swap? I used the hans otten schedule back then but I see I have also cut two resistors (R166 and R167) which normally provide 5V to the VDP pin 26 and 27 but I can't see that in any description. Is this nescessary?

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Por Jipe

Paragon (1594)

imagem de Jipe

24-10-2007, 19:40

not necessairy to cut R166 R167
check
pin 27 -> ground
pin 21 -> +5V
pin 4 -> ground
click in the cassette relay -> no rom or no ram valid
put a 64k cartridge expension in a slot and see if MSX work
if work check RAM
if no work check rom or a wire cut

Por OeiOeiVogeltje

Paragon (1426)

imagem de OeiOeiVogeltje

24-10-2007, 22:03

jipe how do you know this?

where did you get that info?

(just curious)

Por Jipe

Paragon (1594)

imagem de Jipe

25-10-2007, 11:22

no manual no book just personnal experience and curiosity

just expand and repare more 8250 55 80 HB700 Turbo-R
expand -> no work -> search error -> often PCB wire broken when desold Ram

if you desold the ram inside the MSX and Insert external Ram in cartridge the MSX works perfectly
i don't try on Turbo-R i have a doubt because Ram is directly on R800

Por Erikie

Champion (324)

imagem de Erikie

29-05-2008, 13:37

not necessairy to cut R166 R167
check
pin 27 -> ground
pin 21 -> +5V
pin 4 -> ground
click in the cassette relay -> no rom or no ram valid
put a 64k cartridge expension in a slot and see if MSX work
if work check RAM
if no work check rom or a wire cut

Does this also apply for the nms 8250? As I just built in a v9958 in my 8250 and the screen is not looking as I want. It is blue but not syncing correctly.
I did the following:
removed R166 and R167
wire from pin 4 to 20 and 27
and wire from pin 21 to 58

Por Jipe

Paragon (1594)

imagem de Jipe

29-05-2008, 14:26

8250 and 8280 are same board
just video digit board is different
check all your wire around the VDP because then desold you can breaking one or many wire

Por Erikie

Champion (324)

imagem de Erikie

29-05-2008, 14:54

Indeed I am already checking out all pins from vdp to other connections. As I had no sdip socket I soldered the new vdp straight into the pcb.
But I will also wire it according to your instructions. Hope it works out!

Por Jipe

Paragon (1594)

imagem de Jipe

29-05-2008, 15:31

have you the schematic of 8250 ?
check wire one to one with a multimeter with beeper
no miracle with R166 R167 connecting -> is same working

Por Erikie

Champion (324)

imagem de Erikie

29-05-2008, 15:34

I have the original service manual Smile
at the moment one of the 2 pins of R166 / R167 is unconnected which is strange to me.
with the resistor in it is connected to at least something.

Unfortenately my multimeter has no beep ...

Por Erikie

Champion (324)

imagem de Erikie

29-05-2008, 19:59

Well my machine works again. IEither I connect my rom not correctly so the msx logo is not displayed very well or something else is wrong.
Does someone have a good 2+ subrom for me? I downloaded the one from Hans0 Site in a 27c512 eprom ...

Por Jipe

Paragon (1594)

imagem de Jipe

29-05-2008, 21:39

sure this rom work fine
you must added PORT F4 decoder for all function

http://www.msxarchive.nl/pub/msx/mirrors/msx2.com/hansoranje/F4-LatchenAdresdecoder.JPG

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