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

By mohai

Paragon (1031)

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.

By Jipe

Paragon (1625)

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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By Repair-Bas

Paragon (1176)

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.

By Jipe

Paragon (1625)

12-12-2010, 18:00

i know 2 different model of video board in 8280

the older have a little board near

By Jipe

Paragon (1625)

12-12-2010, 18:13

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

By 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?

By Jipe

Paragon (1625)

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

By mau_rizio

Resident (49)

13-12-2010, 23:54

What kind of modification?

By Jipe

Paragon (1625)

14-12-2010, 12:28

just the synchro signal with the V9958

By 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