Couple of questions about SVI-738..

By Mirsku

Supporter (4)

Аватар пользователя Mirsku

07-01-2010, 21:49

Hello to everybody.
I just managed to get Spectravideo SVI-738 with Finnish manuals and original carrying case from a Finnish auction site.
While I was waiting for it to arrive I took a little view to various MSX related sites, hoping to find any good information about that specific MSX model, and I learned that it could be modded into an MSX2 machine.

So it arrived today and I cleaned the mainboard from any dust (it was a lot cleaner than I thought Smile ) and tested DD floppy drive with it, and since it would work I´m planning to add it into it later after I get it to fit better. It seems that it is the model with 2 vram chips and 2 missing spaces. And there is empty space for Real time clock too.
Since it is in very good condition and pretty clean I decided not to waste the V9938 chip on only 16k of vram so I have a couple of questions for the gurus.

- I was not able to find the 64kb 4bit SRAM chips from anywhere but I found "64k x 4 120ns DIP18" labeled DRAM chips from Finnish electronics store so will they work too? I am going to solder the "holders" for chips, or whatever they are called, first since I am not very skilled with soldering.

- The old DD floppy drive I found before worked fine (placed switches to 0 and RY positions) so I´m going to just put it in after I make something to hold it, but will it be able to read DD floppies too well? (I mean that when I tested with SD floppy it worked but is there something with bios or something that works as a bottleneck?)

The last thing is that if I would like to make it into full MSX2 would MSX2 roms from any broken MSX2 work fine or do I need some sort of hacked roms since I have Scandinavian keyboard layout?
I know there are couple of Finnish MSX gurus out there so there might be some sort of "MSX2+SCN keyboard" solution..

Sorry for my bad English, when it comes to technical related terms it just goes "what the heck is that called in English?"
And of course I can send pic of the mainboard if it is needed.

-Mirsku

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By Manuel

Ascended (19273)

Аватар пользователя Manuel

07-01-2010, 22:59

http://msx.retro8bits.com/msxdocs/sviombouw.pdf might help, thanks Hans Otten.

By Mirsku

Supporter (4)

Аватар пользователя Mirsku

07-01-2010, 23:17

I have already looked into that pdf and that is why I asked about the chips. I mean is there anyone who used DRAM chips instead of SRAM chips to confirm that they will work? Anyway what is the difference between those two? timing?
If somebody confirms that the chips I mentioned works and have tested them, I will buy and solder those as fast as I can after the store restocks them Big smile

By Leo

Paragon (1236)

Аватар пользователя Leo

08-01-2010, 11:04

the chip soundss the same, you can give a try if you solder sockets for ram chips.
I recently bought a bunch of 256kbit x 4 on ebay and i have not found any 64k x 4 bit recently.
i have unmodified 738 also so any news on your mods are interesting !

By NYYRIKKI

Enlighted (6016)

Аватар пользователя NYYRIKKI

08-01-2010, 15:29

Yes, you are going to need hacked ROM's in order to bypass the fact that SVI-738 does not have RTC. (Sure you can also build RTC, but I don't think it is worth the trouble.)

How ever there exists already hacked Finnish MSX2 ROM's for SVI-738. Mail me if you need them and I'll dig them up... I should have them somewhere... I've added also some other usefull functionality like selecting Hz mode on boot by holding "H"-key down to the ROM's.

By Stt1

Hero (615)

Аватар пользователя Stt1

16-01-2010, 01:55

I should have plenty of those 64k x 4 bit chips. Also, I should have a set or two MSX2 ROMs for SVI-738 somewhere here unless Nyyrikki finds his.

Mirsku: you wont be able to use the DD-drive without ROM-upgrade as the old ROMs support only 360kb drive.

Building up RTC isn't propably worth the trouble. You would need also a RTC-chip from one MSX2 or build your own version...

SVI-738 modifications are not too bad for a beginner, there is quite a plenty of room for making soldering and when you're careful all should go just fine. Also, you should consider changing one resistor from audio line for fixing fm and scc-sounds. RGB-connector wouldn't be too bad either as the video-out quality is quite bad (imo), but needs a minor modification to the case as well. If you want to go all the way just for hobby, you can go even further than MSX2...

- Saku

By Mirsku

Supporter (4)

Аватар пользователя Mirsku

17-01-2010, 19:41

Mirsku: you wont be able to use the DD-drive without ROM-upgrade as the old ROMs support only 360kb drive.

Umm the first thing that I did was replacing the floppy drive. I used old Panasonic HD drive (and finding that drive wasn´t easy) that didn´t have jumpers but had little switches near the cable connector that allowed to change it to RY and 0. And it reads floppies that are formatted with dos and have tested couple of those homebrew games with it and it reads fine but haven´t tested if it can format disks.
Upon testing I found another little problem and Nyyrikki already gave instructions to that. The chip that controlled the joystick movement was bad.

At the moment the project is little frozen because the shop where I was looking for suitable DRAM chips has nothing left so I just have to wait until they restock, after that I´m planning to do the necessary upgrades and I was planning to take a couple of pics becouse I haven´t found pictures of upgrade from anywhere and they would have been really helpful so I hope somebody finds SVI-738 modification a little bit easier with pics and of course very good information there is floating around already Smile

And by the way are you from Finland too? If I could get suitable memory chips and roms without waiting (and hoping that they will really restock those chips) I could start soldering asap.

That RGB mod involves using capasitors to boost the signal? Is it just to solder wires from chips legs and other ends to the connector (for example normal vga connector) and adding caps in middle of those wires or does it need something else to be done?

I already ordered another MSX (VG-8235/20 with necessary upgrades) to stay the way it is so the SVI can be upgraded and modded further whenever it is necessary.