Philips NMS 8250: Problems with video output

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Door 8its

Expert (71)

afbeelding van 8its

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

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Van assembler

Champion (404)

afbeelding van assembler

05-11-2011, 10:34

I think this is a rom or vram problem.

with a game inserted, the graphics are OK?

Van Manuel

Ascended (18394)

afbeelding van Manuel

05-11-2011, 11:16

I agree Smile

Van 8its

Expert (71)

afbeelding van 8its

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

Van 8its

Expert (71)

afbeelding van 8its

05-11-2011, 11:21

Is the rom or vram problem, how it solves?

Van assembler

Champion (404)

afbeelding van assembler

05-11-2011, 11:24

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

Van 8its

Expert (71)

afbeelding van 8its

05-11-2011, 11:33

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

Yes

Van lovemsx

Resident (41)

afbeelding van lovemsx

05-11-2011, 11:44

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

Van assembler

Champion (404)

afbeelding van assembler

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)

Van slowerisbetter

Master (194)

afbeelding van slowerisbetter

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

Van 8its

Expert (71)

afbeelding van 8its

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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