CRM14 Monitor image too high on screen - Space invaders pt2

[highjon]

Hi guys - looking for advice.....
I have been slowing trying to learn how to fix  the monitor in my old Space invaders Pt2 -  monitor CRM14 M
The image is sitting too high on the screen, ie. I cannot see the scores or UFO at the top of the screen. The adjustment pots for horizontal and vertical cannot adjust this out.
I have found the jumpers for vertical positioning, but because the screen is turned on its side, this adjust the image horizontally.
 I have looked for vertical jumpers and can see some that are connected to large polypropelne capacitors. Funny thing is that they are around the area of "cap 53" which is not fitted but has a component type & value on the circuit diagram.
image attached - indicating large cap at pin marked width and a couple of pins marked W & M, about 60mm apart, but have nothing connected - although these caps  values are shown on the manual
I got the manual here - http://www.arcadecollectors.co.uk/techinfo/arcade-manuals/
This monitor did work correctly before, but developed ROM problems where by I sent the game board to a guy to upgrade the 10 x roms for 1 x rom. I then got gameplay but with an unstable image / rolling. Changing some caps and transistors around the horiz/vertical deflection circuit and now the image can tune to be steady, but sits too high. Vertical phase? ( monitor on its side)
 The variable resistor which controls the vertical height is shown in the manual as being a 0-5K, but measuring this proves it to be only 0-2.9k, could it be as simple as changing this pot ?
Please understand I am a bit clever with pinball machines but a bit green on the monitor front.
Any advice or ideas would be gratefully appreciated.
 
thanks
John

ps - your site has the most difficult verification letters I have came across - would have joined ages ago but couldnt crack the code lol