HB-F9S v9938 partially dead?

Expert (76)

25-12-2015, 17:09

I was having some problems with text modes as I posted here:
http://www.msx.org/forum/msx-talk/hardware/scramble-characte...

but today it seems the video chip has partially died.

I get the MSX boot logo but then when it supposed to show the basic/MSX-DOS prompt the screen goes black . I can briefly see Nextor detecting devices messages but after the CF card is detected the screen goes black. I still hear the keyboard clicks through the TV speaker though...

If I plug a game cartridge or load a autoexec floppy disk I get to the game and the video works fine. I dont know much about the MSX hardware but it seems the text modes (if theres such a thing) are not working.

Im inclined to belive the graphic chip is dead, but before I try to replace it I would like to know if it could be something else... maybe the video RAM?

By Algorythms

Champion (287)

25-12-2015, 17:33

Wait until it boots into basic.
Type:
color 15,0,0
Is the text visible? If so you can save the settings by typing:
set screen

By SuchAGoonie

Expert (108)

25-12-2015, 17:26

Maybe you'll find something in this topic. It also had an MSX with messed up output:

http://www.msx.org/forum/msx-talk/hardware/hit-bit-wbroken-graphics

By Algorythms

Champion (287)

25-12-2015, 17:32

I see you were having problems with the text mode before this. Did the characters appear correctly until the screen scrolled?
If so, I have the same problem with my Turbo R, and in my case it is because I have changed to a faster crystal in my MSX. My original (28.xxx MHz ?) was fried, so I connected one 40MHz and one 32MHz crystal which I can switch between.
But my vram is not fast enough I believe, so when I switch to Z80 mode the text mode behaves like yours when it scrolls.

By blackmsx

Expert (76)

25-12-2015, 18:02

Algorythms wrote:

Wait until it boots into basic.
Type:
color 15,0,0
Is the text visible? If so you can save the settings by typing:
set screen

hahaha! it was the color attributes in the screen... sorry, my bad. Since I was having problems before I assumed the video chip was dying...Thanks for that, it worked.

I have indeed problems with the text in mode 0 either in 40 or 80 columns (works fine in mode 1). The text is fine until it starts scrolling. But this only happens when I have a Sunrise IDE with a CF card plugged in...

By sd_snatcher

Prophet (3425)

25-12-2015, 18:16

@blackmsx

Try running Kightmare to check if there's any screen corruption. After that downgrade back to IDE250.DAT and also check if the problem persists.

@Algorythms

The solution to your case might be simple: you must add a BAT95 diode to connect the /WAIT pin of the V9958 to the /WAIT pin of the slot-1. Then, type the following command on BASIC and check if the problem stops:

VDP(26)=4

Or you can just try to buy the correct 28.63636MHz crystal at eBay.

By Jipe

Paragon (1437)

25-12-2015, 18:07

try to desold the battery BATT1 GB50H and reboot
the screen parameters is saving in the chip clock ( integrated in the S1985 System Contrler )

By blackmsx

Expert (76)

25-12-2015, 22:06

sd_snatcher wrote:

@blackmsx
Try running Kightmare to check if there's any screen corruption. After that downgrade back to IDE250.DAT and also check if the problem persists.

Thanks for the advice. I tryed both things. I dont see any glitches while playing Knightmare. I flashed back to IDE250.dat but the scrolling text problem persist. As far as I can tell, as soon as the CF card is detected the problem appears...

By RetroTechie

Paragon (1563)

26-12-2015, 12:21

Can you try the exact same thing that causes the problem to show, on other MSX machine(s)? With the same IDE interface, that is. Preferably another HB-F9S of course, but checks on other models would also help.

Can you run a mapper test program on your HB-F9S? And if available a program for testing VRAM too? And for both I mean programs that exercise the entire (V)RAM, not just test how much there is.

To others: is there some easy way to read back the Flash EPROM's contents from that Sunrise IDE interface? That writing the Flash chip works, doesn't mean it's working 100% correct (depending on how well the flashing utility does its job).

Given the symptoms described so far, I very much suspect a memory problem. If it is, you just have to determine which memory is at fault. If it isn't, it would be good to rule out as a possible cause. Other than that it looks like the kind of thing you'd have with a badly working turbo circuit. But I see no mention of that being part of the equation here...

By blackmsx

Expert (76)

26-12-2015, 21:19

Thanks again for your help.

I tryed on a MSX1 machine I have and theres no text problem. Althoug the situation is different because the system isnt loading from the CF card... So I cannot do the same tests on this machine really.

It is worth to mention that I have internally upgraded the HB-F9S to 512k, with a single SRAM chip (I havent added a turbo circuit though). I also thought that might be the problem so yesterday I reversed the modification and put the original 4 RAM chips back in. The problem was still there....There is always the chance I've damaged something while doing the memory upgrade...

I've runned Testram and it detects and test the memory succesfully. Is there any other memory test software to try out?

By flyguille

Prophet (3028)

26-12-2015, 21:30

the scrolling has nothing to do with RAM, if it don't hung, z80 and RAM are stable ok.

The scrolling routine is a VPEEK + VPOKE running all the name table, so maybe reading VRAM is the issue, not VPOKE, by that reason, you see games or logo screen ok.

But, vpeeking is also used for know what command you entered before run it.

Do you have, erratic "syntax i/o error" on correct commands?