Phillips VG8235 - Color video + V9958 Problems...

Supporter (11)

04-11-2009, 23:11

Hi, there...

Does anybody help me? The question is: My 8235 are crazy!!! This colors appears descolored or b&W...I just substitute an X-Tal...various models (Pal-M/N/B/G and NTSC) and nothing!!! Any idea, my friends? Second...I bought a V9958 and changes a old VDP (includes jumpers 1,4, 27 and 21,58...in Hanso´s site, i found more information as capacitor 100nF between 20,21 pins...In Gilberto web site, plugs pin 26 with Z80 R1) but...My computer turn on, but a bad signal (interferences, screen not center and in graphic mode, turns on a vertical in TV)...I check PSU and works fine...Any idea?
Thanks in advance...
The Wall

By thewalll28

Supporter (11)

04-11-2009, 23:16

More one qustion: I adapted a commodore A520 for use in 8235, but don´t shows colors too...Sorry my bad english...Thanks again

By thewalll28

Supporter (11)

05-11-2009, 21:52

anybody? I discovered whom encoder unit blue bad signal...Red and Greenm,ok!! well... VDP (still 9938 ) could be a problem?
thanks in advance
cheers

By Leo

Paragon (1236)

05-11-2009, 21:59

i had changed the vdp on my vg8235 like 5yrs ago.
I remember the colors were darker and yellowish , and the beginig it was very very dark, and i did a fix, i dnt remember (hehehehe ) i will have to open it after so many years to see what i did i remember it was
a wire from vdp to direct rgb output (piggy fix)

By thewalll28

Supporter (11)

06-11-2009, 03:49

Hi, Leo...thanks for idea...I plugs 3 pins of RGB from V9958 to commodore a520 and, aparently works, but...2 problems I don´t understand...
1) I plugs in commodore a520...Works fine, but in B&W...Do you knows if A520 supplies internal Xtal frequency ? Encoder unit not regonize a blue signal...So, I uses a A520...
2) MSX2+ Roms are in 60 HZ VDP Int, buit the screen would be in 50hz because TV vertical dispates!!! Any idea?
Thank you...
Cheers

By Leo

Paragon (1236)

06-11-2009, 06:37

i am not sure to understand :
msx is ok.
But A520 is B&W only ? dont know much of commodore, maybe the monitor should send
a signal to th a520 so it can understand he can switch from B&W to color ?

For 50/60Hz you can go into basic and type vdp(10) = 10 or vdp(10)=2 to choose 50 or 60Hz.
you can make a little .bat file in msx dos for that.

But i guess any time you will change screen it will get back to rom default value (like games )

Beware connecting direct wires without buffers can ask to much current to the vdp buffers,
it may burn : just ot let you (i am lived with it during a year though )

--> that is the reason why i look after a bargain for a 41cm lcd TV for my msx

By thewalll28

Supporter (11)

06-11-2009, 21:50

Leo...Many thanks again...I typed in Basic VDP(10)=10 and VDP(10)=2 and same results...Display in Pal mode...don´t show in NTSC mode...I uses VG 8235 in screen 0, width 80...But,not stop flickers dispaly...What´s happening?
Thank you

By MäSäXi

Paragon (1884)

07-11-2009, 08:57

i am not sure to understand :
msx is ok.
But A520 is B&W only ? dont know much of commodore, maybe the monitor should send
a signal to th a520

A520 is a TV modulator for Amiga. Not for monitor use.

See:

http://www.amiga-hardware.com/showhardware.cgi?HARDID=725

By Leo

Paragon (1236)

07-11-2009, 13:44

you mean A520 modulates RGB or composite output from MSX2+ ?

if you put composite from a japanese msx2+ , it is ntsc and color coding is different from PAL which is also different from SECAM.

Typically when you want to plug a wrong standard you end up with BW image.

A520 is multistandard ?

By DD

Expert (88)

07-11-2009, 21:25

If you have flickering with VDP(10)=2, do you have a NTSC TV system then??

If VDP(10)=0 stops flickering, then your TV is NTSC and won't display colours with a standard 8235 and probably the A520 neither... I am not sure if the PAL ecnoder of the 8235 can make NTSC, if your TV supports SCART you can use that. Don't forget to pull pin 16 to +5V via a 75Ohm resistor to activate the RGB input of the SCART.

By thewalll28

Supporter (11)

08-11-2009, 02:50

Yeah!!! A520 is TV modulator and I plug Philips in an TV NTSC video mode...And no!!! My TV don´t have scart port...Simply A/V mode...I plugs directly RGB pins from V9958 to A520 RGB inputs...8235 encoder unit is a problem in output blue signal...don´t works...Well, I try command VDP un basic and looks stop flicker...So, I post rgis result here again...
Thanks for all MSX friends...
Cheers