failed PCB circuit - anyone able to have a look? (long shot)

["slashcomfort" <xslash@xxxxxxx>]

I have a gate opener circuit which worked up to a few hours ago.
Rather than go through the process of sending it back to be repaired,
I'm thinking it will be a simple component thats gone in it and so
I'm going to ask those experienced with power supply type circuits to
see if it obvious. Will send jpg of board to those interested in
having a quick look.

Nothing looks blown, all fuses are ok, no components looked cooked

The unit takes 230v AC into a toroidal transformer and outputs 12v AC
(yes, AC). This work ok as when the board fails, i still see 12V on
the board from this. Somewhere along the line it gets converted to
12vDC and 5vDC.

Theres a LED labeled 5vDC that is always normally on, since the fault
this starts off bright as it should, then slowly fades (after about
5 - 30 seconds - the board still works as it should during this short
period but its not long enough to open/close the gates) - this is
what appears to be at fault - I beleive the boards brains work off
5vDC and its failing.  Also, theres a Normally open switch that you
press to activate the gate, this read 5v while the LED is bright
(normal) then just drops to zilch. To me (and i havent done
electronics for years) primary components not including the relays
(used for switching motors on/off) are a couple of transisters
mounted on a heatsink (power conversion?) and a large capacitor.
Could it be the capacitor has blown and not holding its charge?
email me for a photo of the board if interested

any help appreciated

thanks

Ade