Dear Group, I am a fairly new member and this is my first posting, but I think I can help on this one. I have had considerable experience with R1225 PA meltdown. It defiantly will not support high duty cycle at full power. In the course of rebuilding I have found three things that allow them to survive. 1) The PA transistor in almost every case is not torqued correctly and has poor thermal transfer to the fairly massive heat sink. I have found that the screws require up to about an additional half turn. I attribute this to significant improvement in heat survivability. 2) The silver solder is a real good idea when putting things back together. 3) Don't run it above 9 amps. This should make about 25 Watts. It seems to hold under worse case conditions at this point. In the extreme when the ambient temperature is like the inside of a closed car left in the sun, additional fan cooling is additional insurance. Best of luck. Would like to hear if anybody else has encountered this transistor torquing problem.
BRIAN ALESIO B.A. Radio Company Inc. It's not so much a defect as it is asking the rptr to do more than it was designed for. It may be a 45 watt PA but in rptr use, medium to HD rptr use, drop it down to about 25 to 30 watts out of the PA. Enjoy what you get thru the duplexer. Asking for more will melt the PA. The earlier units had a temp controlled fan that only came on when the PA was about to melt. The next generation of power supplies came with a switch to turn the fan on permanently. You will probably be able to fix them without the manual. Most of the time the PA transistor collector got hot, melted the solder & the chip caps moved (slid down the pcb due to gravity). I repaired these on a regular basis without needing new parts unless the damage literaly burnt the pcb around the collector lead. I removed the chip caps, removed the solder on the collector tab & trace & resoldered it all back in with silver solder. This, along with turning the factory output down, made them last a long time even under HD casino use. I think it took me maybe 45-60 mins to get it all apart, fix it, reassemble, reinstall. Lots of times I did it in place at the customer's premises. rtc
