Hi,
A Multimeter is never enough for failure analyzis...
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
This I´ve learned over 20yrs ago in a "painful" way and it´s still valid.
Looking at the 5V for the Controlboard with scope, first setting the timebase to 10s because I wanted to see the signal rising.
But there´s no rising, there´s a huge noise on the dc-signal, reduce timebase to µs, aha...
Something is heavy oscillating and the signal remains even when you disconnect the plug from the controlboard, so it´s definetly on the supply board.
The board itself is "simple" as it can gets, several aux voltages from the transformer goes through rectifiers and then stabilizing with classical 78/79xx types, plus one 317.
And where every other voltage is clean, the 5V for the controller is oscillating.
So the 5V regulator must be replaced.
I got several ones here, but not in fully isolated housings.
Maybe for testing I´ll take one.
So or so, I think this was it...
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/xcool.gif.pagespeed.ic.cOxV6sPNRd.png)
If I´m right, next step will follow, what to do with the touch panel and (perhaps) with the backlight.
Martin
(edit why are the pics "shuffled"...it´s not my order I´ve placed them)