# RGBs video signal unstable

#### Simon_m74

Jul 25, 2016
31
Hi
On my Virtual Reality machines, there are two types of LCDs used in the headsets - depending on the machine version.
On version uses Epson LCDs, while the other uses Panasonic.

The machines also output to an external display via a 9pin Dplug - CGA (RGB & sync)

On an old CRT, this works fine, with either a system for Panasonic of Epson.
With LCDs, using either a CGA to VGA, or CGA to Composite - with an Epson system its fine, but on a Panasonic system, the video output is unstable.
Effects like no sync on some LCDs, or vertical shaking or odd colours..

I have found a manual with a note in it... so I hope this helps you help me making the video stable on a Panasonic system.

In the manual, it states that the video output is:
Type : RGB Analogue
Volatege : 1v Pk to Pk
Impedence : 75ohm
Connection 9 pin D-type
Line period : 64 nano seconds (15kHz)
Field rate : 49.92 Hz
sync voltage : 0.3v
Now the interesting bit:
Sync type : Printed as Combined Sync (+ve) - I believe this is for the panasonic screens
The combined has been crossed out, and hand written as Neg Going TTL. Which I imagine is for the Epson screens

Now, my hope is, that I can get a stable output on Panasonic systems, as most of my machines are Panasoinc systems.

Thanks

Simon

Jul 25, 2016
31
any ideas?

Thanks

#### kellys_eye

Jun 25, 2010
4,880
I'm confused.
I can get a stable output on Panasonic systems
What do you want? A stable OUTPUT or a stable video INPUT?

The whole wording of your query just doesn't make sense (to me) and I can't figure out what you've got, what your issue is or what you want.

The video signal needs to match the monitors requirements - obviously. Either convert the video signal to match the monitor or use a monitor that accepts the video.

#### Simon_m74

Jul 25, 2016
31
Hi
Sorry for confusion,
Right - the output from the VR machine, shows to be unstable when connected to an LCD panel, but fine on a CRT monitor/TV.
Depending on the LCD panel/TV I use, I get from best, a good image, that slowly jumps up and down a few pixels, to randomly going out of vertical sync, random large black horizontal bars and random colours, usually heading towards purples.
I have recently read that as a scart RCBS connection, uses the composite line a the sync - and that a lot of modern monitor/TV systems require a resistor on the sync line, otherwise the voltage is too high.

I have installed a resistor - but have not yet had time to plug it in to check - I hope to tonight,
The resistor / sync line being too high - does to me sound like its what could cause the instability ?

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