Philips NMS 8250: Problems with video output

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By 8its

Expert (71)

8its's picture

05-11-2011, 10:05

hi, somebody can identify and solve this problem? connected by scart cable and RF also, with the same result.
A lot of thanks

Img1
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By assembler

Champion (378)

assembler's picture

05-11-2011, 10:34

I think this is a rom or vram problem.

with a game inserted, the graphics are OK?

By Manuel

Ascended (15802)

Manuel's picture

05-11-2011, 11:16

I agree Smile

By 8its

Expert (71)

8its's picture

05-11-2011, 11:19

I think this is a rom or vram problem.

with a game inserted, the graphics are OK?

graphics not works with a game

By 8its

Expert (71)

8its's picture

05-11-2011, 11:21

Is the rom or vram problem, how it solves?

By assembler

Champion (378)

assembler's picture

05-11-2011, 11:24

If you start the MSX with a cartridge, graphics are corrupted too?

By 8its

Expert (71)

8its's picture

05-11-2011, 11:33

If you start the MSX with a cartridge, graphics are corrupted too?

Yes

By lovemsx

Resident (41)

lovemsx's picture

05-11-2011, 11:44

Hi, change vram's chip and solve the problem, good luck Wink

By assembler

Champion (378)

assembler's picture

05-11-2011, 11:59

Then is a VDP or VRAM problem.

Try this basic program

10 SCREEN 5
20 FOR P=0 TO 3
30 SET PAGE P,P
40 FOR x=0 TO 255 step 5
41 LINE (X,0)-(X,191),RND(1)*16
42 NEXT
50 FOR Y=0 TO 191 step 5
51 LINE (0,Y)-(255,Y),RND(1)*16
52 NEXT
70 A$=INPUT$(1)
80 NEXT

It will draw some lines in 4 diferent pages of VRAM. Press any key to change page.

If only some of the pages are corrupted in the test, the problem is the VRAM.
If all the pages are corruptes, the problem can be the VDP or the VRAM.

You can check the board if there are some bad solderings (first you should locate the VDP and VRAM CHIPS)

By slowerisbetter

Master (194)

slowerisbetter's picture

05-11-2011, 12:14

A friend of mine had (in the 80s) something like this when he pulled out a cartridge while the computer was on. He 'debugged' the problem (nothing to lose as the computer was now unusable) by sticking a paperclip in the cartridge port randomly and lo and behold in some position it solved itself. He had his MSX-2 working for YEARS after that with that paperclip stuck in slot one. Not saying you should try that though, the above tests/solutions sound a bit more scientific Wink

By 8its

Expert (71)

8its's picture

05-11-2011, 13:14

Then is a VDP or VRAM problem.

Try this basic program

10 SCREEN 5
20 FOR P=0 TO 3
30 SET PAGE P,P
40 FOR x=0 TO 255 step 5
41 LINE (X,0)-(X,191),RND(1)*16
42 NEXT
50 FOR Y=0 TO 191 step 5
51 LINE (0,Y)-(255,Y),RND(1)*16
52 NEXT
70 A$=INPUT$(1)
80 NEXT

It will draw some lines in 4 diferent pages of VRAM. Press any key to change page.

If only some of the pages are corrupted in the test, the problem is the VRAM.
If all the pages are corruptes, the problem can be the VDP or the VRAM.

You can check the board if there are some bad solderings (first you should locate the VDP and VRAM CHIPS)

impossible write! Smile After three lines i don't know that had written ¿?¿?¿

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