intermitent power on and off veiwsonic va912

HI all i have a old veiwsonic va912 used as a extended desktop in a 4 monitor set up, a bit ago it started powering off then on again without any user input. im not exatly new to motitor problems so have managed to narow it down first a discription of the fault

1. after the monitor is powered on from cold it will run no probs for 5 min or so
2. after this it will turn its self off competly no power leds no turning back on if i press power botton its as if the power cable is unpluged
3. after 30-60 secs it will power back on
4. after 30-60 secs it will power off again and this will reapeat indefenatly
5. so after some looking around i found this site and a forum that seemed to have same issues as mine the main marked up ansew was yes its prob the power board buy a new one, one of the other ansewers did metion it could be a overheat problem so i striped the monitor again (id already had it in bits and did a visual inspetion for bulged caps with no look) and did note that some solder joints had burnt, so i resoldered and the prob was still there but with the board exposed the screen stayed on for longer, and with a fan blowing on it it stayed on indefenatly though after some time it got very buzzy noise wise and lots off tiny horazotal lines started to blurr the picture.
6. so i belive some of the CAPs are bad is there a way to test them? well on board ive orderd a multi pack of CAPs but would like to narrow it down obviose start are the solder joints that were burnt, id rather not just replace all of them as i am boand to runn in to this prob again at some point and would like to know a effechent way of narrowing it down and only replaceing bad CAPs
7. Thanks for reading and Thanks for any responses
8. im going to strip a tv with a smashed screen and see if any of the CAPs are the right size and report back with any thing i find Thanks again all :)