Overscan with Sony KX-27PS1 via SCART

[Kong Jnr.]

Hey guys,

I'm running a KX-27PS1 which has a sort of fisheye shaped tube and as such, has a problem with overscanning in those areas, i.e how much ships you have left in Galaga.

I've searched and searched for a method of adjusting the overscan amount though due to it's age, it might not have that functionality. Most horizontal games look and feel fine though playing vertical games such as Galaga and Donkey Kong usually have the words "High Score" up the top missing and a similar amount at the bottom missing.

I was wondering if anyone has any idea on how to display these vertical games in a slighty 'squashed' down view or any other tweaks that might help with overscan until/if I find a way to physically adjust it on the monitor.

I'm running MAME 0.134 with Soft15khz over a VGA to SCART connection.

Thanks heaps in advance guys!

[grantspain]

if its quite an old tv then you would almost certainly find a vertical and horizontal size adjustment pot on the actual monitor chassis

[Kong Jnr.]

I've located three pots inside, one marked H.Stat, one (as far as I can tell) marked SCRN and another marked FOCUS. Haven't had the guts to turn any of them yet until I find out what they do

[grantspain]

focus and screen volts are on the flyback,screen volts is a pre-brightness and focus is self explaining
i do not know what h.stat is-something to do with stabilisation of high voltage so do not touch this

[Jack Burton]

From what I can gather online H. Stat refers to horizontal convergence.  If the convergence of your monitor is fine I wouldn't bother it at all.

I wouldn't touch any of the three unless something looked especially wrong with the image.

It would probably be easier to try to adjust your screen size through software at first.  Some tweaking of modelines in Soft 15khz may give you the result you desire. 

But first try a resolution that is slightly higher than your games intended resolution.   If done correctly this should put the image in the center of the screen, and the unused lines will be off in the overscan.  This should give you a very similar visual result to want you want.

[Kong Jnr.]

Hey Jack, I played around with a few resolutions with Galaga, (as it turns out, it seems only 288 line games that give me grief) and the only one that displayed the full image was 640x480 though that was roughly 50% of normal size and looked a bit like a postage stamp

I recently discovered in the MAME 0.134 menu 'slider controls' which lets you shrink the image down. I managed to shrink it down vertically which screwed up a few graphical things but I'm sure if I shrink it by the same amount on the horizontal it should look fine. I did notice a bit of lag when doing this with Frogger, not sure if it uses more CPU to shrink the image down. I'll do some more tests and let you guys know!

[Jack Burton]

hmmm, is 400x300 one of the default resolutions added with Soft 15khz?  If not I think that may be worth a try.  

Are you attempting to run Galaga in vertical mode or horizontal with pillarboxing?

[Kong Jnr.]

Hi Jack, I've been attempting to run in on a horizontal display with pillarboxing. 400x300 doesn't appear native to Soft15khz so i'll have to research how to add custom modelines to Soft15khz and work out all that out.

I just tried using the slider options to scale the image down but couldn't hit a sweetspot where all the text was correct. I took some photos with my phone to illustrate it for posterity.

Unscaled / Native


Equally scaled


You can see the definition between the A and M is lost when scaled.