Philips VG 8235 disk drive

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Van carlsson

Supporter (5)

afbeelding van carlsson

07-01-2008, 00:56

You have to change the diskrom, the drive cable, a little modification on the main-board and the best is to to change the power supply.
Sorry to bring up an old topic, but I own another VG-8235/00 that is fitted with a modern PC floppy drive but only 360K capacity. I have downloaded a Disk ROM image and burned a new EPROM. When I tried to format a floppy double-sided, Basic said "Bad parameter". After disassembling the computer, I found the floppy drive cable was assembled to fit a NMS 8245 instead of a VG 8235.

I found a guide by HansO 2003 which I believe strives to support 720K floppy drives. It mentions 2-3 wires should be connected to LF58, LF65 and LF61 in order to work on the 8235. Is this what you refer to "a little modification on the mainboard"? If so, could anyone explain which end of the three pin capacitors (?) I should solder the wires to? As the cable was wired, the side select pin was going to pin #8 (side select on the 8245, but drive select 2 on the 8235), and ditto for the "in use/open" pin.

Van mohai

Paladin (957)

afbeelding van mohai

15-01-2008, 11:13

I have a 8235/00 too. Actually, drive is changed and diskrom too.
If you do not want to bother with soldering, there is an easy sollution. Just plug a standard 34-pin cable in the "external drive" connector in the back (i passed it bellow the mainboard to where the drive is) and connect to PC drive. Maybe you will need to swap cables 10 and 12 (drive select 0 and 1).
If you do not get atched diskrom, try with poke -609,201, it helps a lot...
I did not use extra voltage regulators also, as 8235/00 power supply is enough if you use only one drive (i was able to connect 2 indeed!).

By the way, do not forget to fix the mapper as it is indicated in the technical manual. This way you will get -true- 128K. Wink

Van Repair-Bas

Paragon (1149)

afbeelding van Repair-Bas

15-01-2008, 14:48

What a horrible schematic is that. Where do you fint that little adapter-print?
Rewire the drive-cable.
Oeioeivogeltje discribed how I change that cable with any extra parts (and ofcourse costs)

Van mohai

Paladin (957)

afbeelding van mohai

16-01-2008, 14:30

Notice that 8235/00 is a very special model. Drive connector is not "exactly" the same than 8245.
8235/20 and others have a very different board. Sollution for them and 8245 is not the same.
For more info on connectors, try http://msx.retro8bits.com/msxdocs/vg8235sm00.pdf and http://msx.retro8bits.com/msxmanuals.html

Van Repair-Bas

Paragon (1149)

afbeelding van Repair-Bas

16-01-2008, 17:28

The 8235/00 has the same connector as the 8245 and the 8235/20
But for both types of the 8235 you need to make a little modifications on the mainboard.

Van mohai

Paladin (957)

afbeelding van mohai

21-01-2008, 18:04

I am sure i did not modify the mainboard at all in the 8235/00 (big board). I only replaced the drive and changed diskrom
Maybe, to get extra signals, like Diskchange, modifications are needed...

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