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View Full Version : Sony Hit Bit 75 MSX - Blue picture via SCART



chinnyhill10
30th January 2015, 23:21
Just taken delivery of a Sony Hit Bit 75B. Have been running it using a fully wired SCART lead into my Samsung LCD TV.

What I've noticed is the picture is slightly washed out when running via full RGB and black is elevated to a dark blue.

If I plug a composite cable into the SCART the colour balance is perfect.

Anyone come across this? The composite seems perfect so I am assuming it is a signal level problem somewhere. Possibly a resistor needed somewhere or perhaps resisters on all 3 RGB lines?

Picture is perfectly clear and sharp, its just the colours are wrong.

Anyone know?

Thanks.

kaosoverride
31st January 2015, 11:11
Looks like the MSX is RGB TTL level (0-5V) so you need to make it TV level compatible (0-1V) like this BBC Micro RGB mod.

Basically you use 220 resistors and should work...

82498

chinnyhill10
31st January 2015, 11:15
Looks like the MSX is RGB TTL level (0-5V) so you need to make it TV level compatible (0-1V) like this BBC Micro RGB mod.

Basically you use 220 resistors and should work...

82498

Fantastic. Thank you so much!

Will print that out and will take it to the shed for an afternoon of soldering and swearing. :-)

Cheers.

chinnyhill10
31st January 2015, 18:06
Put 220's on the RGB channel and a 270 on the sync. Pic too dark now and still hinting towards blue on the blacks.

kaosoverride
1st February 2015, 23:03
From http://msx.hansotten.com/index.php?page=msxmanuals

Take the HB75 service manual.

http://msx.hansotten.com/uploads/msxdocs/sonyhp5575sm.pdf

RGB is made from Y, B-Y and R-Y signals, there are some transistors and resistances at the circuit.

- - - Updated - - -

Page 53 of the PDF. There are some variable resistors for the RGB channels, or the color diferential. Give a try!!

chinnyhill10
2nd February 2015, 00:04
Thanks. Have bookmarked that so I can have a look inside the unit when I get some time.

Given the rewired joystick that came with the unit, it's perfectly possible the previous owner has been inside the unit and tweaked those variable resisters for his own setup.

Will update when I've had a chance to look.

Thanks.