[1000mp] Power supply prob??

[f f]

After putting up  new beam, my MK V starting cutting in and out.  I 
turned it off and let it rest and tried again; same results.  I noticed 
the power supply power light, turning on and then dimming off.  It has 
been hot in the shack, so I tried it last night in cooler wx and it did 
the same thing right during a PSK QSO.
Anyone have the same problem?  I did find the schematic on the net, but 
will see what comments I get before tearing into it.
Thanks for the help.
Jim, K6UUW