NMS8280 video problem.

Resident (49)

12-12-2010, 16:54

After a long time i've turned on my 8280 expanded to 2+,
it's working good but the video output is waving a little bit.
It seems like a demo effect
Thinking it can be a power problem i changed the power source with another one without this problem, but nothing changed.
What i can do?

I've seen that some 8280 have a metal plate over the disk drives, mine hasn't. Why it's there?

thank you
mau

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Por mohai

Paladin (1007)

12-12-2010, 17:27

It can be some AC going to video modulator or to VDP chip.
If sond is OK, then problem is only in video circuitry or modulator.

Try to check and change surrounding capacitors specially electrolitic ones.

Por Jipe

Paragon (1614)

12-12-2010, 17:43

the metal plate is a temperature dissipator for drives

the synchro signal is modified on 8280 expanded 2+

but the schematic is here :

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Por Repair-Bas

Paragon (1175)

12-12-2010, 17:53

There are 3 types of 8280's
the 1st one has no plate on the drives.

Did you use another power supply of an 8280?

Try with a voltage-meter to find all 3 voltages on connector PC.
1st without cable, 2nd with cable.

Por Jipe

Paragon (1614)

12-12-2010, 18:00

i know 2 different model of video board in 8280

the older have a little board near

Por Jipe

Paragon (1614)

12-12-2010, 18:13

http://www.msxarchive.nl/pub/msx/mirrors/msx2.com/hansoranje/v9958.JPG

Por mau_rizio

Resident (49)

12-12-2010, 21:10

@mohai: wich capacitors?

@Jipe: my has the little board on the top left of the digitizer board. I will try to verify the scheme you posted.

@Repair-Bas: i used the power supply of another 8280 without that problem.I 'm not so good with those thing, can you explain how to do the test with the voltage-meter?

Por Jipe

Paragon (1614)

13-12-2010, 11:20

i tried to modify this type of 8280 with the small board but the result was not very good
finaly i replace the video board by another model with only one board (8280 broken)
it is also necessary to replace the drill plate with the cursors in front panel

Por mau_rizio

Resident (49)

13-12-2010, 23:54

What kind of modification?

Por Jipe

Paragon (1614)

14-12-2010, 12:28

just the synchro signal with the V9958

Por mau_rizio

Resident (49)

14-12-2010, 12:33

@Repair-Bas: Please, i 'm not so good with those thing, can you explain how to do the test with the voltage-meter? thank you