[ICOM] IC-718 that dies on 30m, revives, dies again

[N4ch at aol.com]

2 things to try, before opening the rig up:   Have  another receiver nearby 
tuned to the frequency U are transmitting on, and also  place a DC ammeter 
in series with the 12 volt supply cabling, so U can listen to  what the Icom 
is doing, and look at how much current it is drawing while  transmitting on 
30 meters.   If the radio draws a lot of current but U  hear nothing on the 
"monitor" receiver, the PA is probably oscillating, and  trying to put out 
a lot of power on some unknown (and perhaps far removed)  frequency.   See 
what an inline watt/SWR meter says........if U see  power (but the SWR 
suddenly jumps to a high value) the RF coming out of the  radio isn't on the 
frequency it's supposed to be on.   This could be  caused by several things, 
ranging from a bad relay contact in the low pass  filter section that's switched 
in when 30 meters is selected to perhaps a bad  case of RF feedback if the 
antenna is near your rig.   Does the  problem go away if you disconnect the 
antenna and substitute a dummy load  ?   I'm assuming the radio works OK on 
the other bands besides  30.   Good luck.
 
73, Herman, N4CH.