[ICOM] IC761 Power supply

[zl3kr]

While operating PSK (approx 20-25 watts out) the overload cut in and 
closed the rig down. After 2 to 3 minutes I switched back on and it 
powered up ok, however as soon as I went to transmit it shut down again.
I repeated this a couple of times with same result but then tried the 
rig on CW and SSB where it was able to run full power, went back to PSK
and it shut down again.
Now on trying to switch on again the overload relay clicks in about 3 
times and shuts down straight away.
A visual inspection of the Power Supply shows no signs of Capacitor 
leakage or overheating on the PC Board.
I wonder if anyone has any suggestions as to the most likely place to 
start looking for the problem please. I appreciate any help.
Alan ZL3KR