mysterious switches

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By HansO

Paladin (672)

HansO's picture

03-11-2005, 22:38

BTW, did you actually check the functionality of the switches? Judging from the texts above, it seems that you're assuming their functions by what other people tell you. My '80 has 2 switches: one for 7MHz (as mentioned by others) and one for KUN-Basic.

Indeed, it can be any function the owner/modder could find nice to do. Thats the beauty of the MSX: so easy to mod!

By msxrestarter

Master (222)

msxrestarter's picture

03-11-2005, 23:00

I will try to carefully dismantle my precious MSX to follow the wires coming from the switches.
Won't be for today however, will first read service manual to know how to proceed with this.
Is there something I need to be extra carefull with ?

By HansO

Paladin (672)

HansO's picture

03-11-2005, 23:13

I will try to carefully dismantle my precious MSX to follow the wires coming from the switches.
Won't be for today however, will first read service manual to know how to proceed with this.
Is there something I need to be extra carefull with ?

Make many photos, so you know where to resolder wires if they get loose!

By BiFi

Enlighted (4348)

BiFi's picture

04-11-2005, 07:07

Most likely there's also a raised diode block to convert AC into pulsating DC, which can be quite hot in a 8280.

I kindof doubt KUN-Basic being a switchable feature. The official KUN-Basic has a CALL BC to initialize the compiler. DOS2 is a known switchable feature. So are 7 MHz, MSX2/MSX2+ selection and composite/S-Video.

There are modified SubROMs which do have a memory counter routine for about every MSX2 type.

btw... for some strange reason Memman crashes when the internal DOS2 is switched on (and booted up)... and msd, when DOS2 wasn't switchable the machine would boot up with DOS2 every time which isn't what you wanted. It's really not set up like in the turboR you know... Wink

to check which VDP is installed try this:

PRINT (VDP(-1)\2)AND31

if it returns 0 it's a V9938, if it return 2 it's a V9958.

By msxrestarter

Master (222)

msxrestarter's picture

11-11-2005, 19:51

Just completed checking the features behind the 3 switches:

left switch: 7 Mhz on/off
middle switch: MSXDOS2 on/off
right switch: S-video on/off

Checked the cpu speed with benchmark/clock program made by A.M.C. de Kinderen (Rijnmond Computer Club).

@HansO: is it normal that if you are using S-video input and you flip the switch to the composite side the image goes to black and white in stead of color ? Question
(is also the other way around : when you're using composite input and you flip the switch to s-video, the image stays on the screen but changes to black and white instead of color)

By HansO

Paladin (672)

HansO's picture

11-11-2005, 20:34


@HansO: is it normal that if you are using S-video input and you flip the switch to the composite side the image goes to black and white in stead of color ? Question
(is also the other way around : when you're using composite input and you flip the switch to s-video, the image stays on the screen but changes to black and white instead of color)

It is. With S-video the color is separate from the signal. The parts remaining are sync + intensity, which delivers a black and white (actuially greyscale) picture.
Everything stays in color btw if you use a rgb monitor. Your monitor is now attached to composite video output?

By msxrestarter

Master (222)

msxrestarter's picture

11-11-2005, 22:09

Monitor is attached to computer with normal scart cable.

By HansO

Paladin (672)

HansO's picture

11-11-2005, 22:31

Monitor is attached to computer with normal scart cable.

Scart cables come in two kinds: fully wired (thick, 21 wires, all rgb+ sync+composite+audio signals) or partly wired (thinner, only composite video and audio). I guess you have the partly wired type or a monitor with only composite input.

By msxrestarter

Master (222)

msxrestarter's picture

11-11-2005, 22:55

Tried another scartcable and works fine now Big smile
Again, thanks for your quick reply !

P.S. With the help of msxfemale I've got me a second 8280, also with some modifications. Will post some pictures soon.

By msxrestarter

Master (222)

msxrestarter's picture

11-11-2005, 23:23

The new 8280 I've bought, has two switches and a potmeter
users.telenet.be/msxrestarter/voorkant%20schakelaars.jpg
users.telenet.be/msxrestarter/achterkant%20schaklelaars.jpg

The right switch is used to boost up the drive loading speed.
When turned on, loading is almost two times faster.
Maybe this switch triggers a 'fast diskrom', have seen this mentioned in almost all e-bay sales of Repairbas.

The left switch turns the potmeter on or off.
When turned on, you can modify the sound : turning clockwise increases the sound, anticlockwise reduces it.
The former owner told me this was neccessary for using his FM-PAC. Seems like sometimes the sound created by the FM-PAC is to high in volume compared to the sound from the MSX soundchip.
However I don't have this problem with my other 8280, so I don't exactly know what is the sense of this modification.
As you can see, the switch&potmeter are connected to C383 (witch has been cut) an to the cartridge port.
users.telenet.be/msxrestarter/cartridge%20aansluiting.jpg
users.telenet.be/msxrestarter/draad%20gesoldeerd%20aan%20C383.jpg

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