{Collins} Interesting 30S-1 Experience



I experienced an odd failure which I decided to share in case anyone else runs into it. My 30S-1 abruptly began blowing plate fuses when I loaded it past about 1KW output (it has the increased screen voltage mod). I also noticed it was taking more drive than normal for a given power output.  When I went to unplug it to prepare for digging around inside, I discovered that the 240 vac plug had backed almost all the way out of the outlet.  A light bulb immediately lit over my head as I realized that the voltage drop across the poorly connected plug must have pushed the current in the plate transformer primary above the fuse rating at about the 1KW output level, especially when I was off resonance and efficiency was low as I tuned. Pushing the plug back into the wall solved the problem. Probably the simplest glitch I ever fixed. Another variation on the classic first troubleshooting question, "Is it plugged in?"

I am using 12 amp fast blows in the plate circuit. A Collins SB recommends changing to 15 amps, which are what is shown on my schematic, though they are labelled 12 amps on the fuse panel. Probably the 12 amp fuses are running close to the line, and it doesn't take much to push them over.  

73,

Ora
W9DJ



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