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« on: December 30, 2015, 1617 UTC »
Hi,
I am trying to recover from a newbe mistake of a couple of years ago. I had purchased an Ameriton 80A amp used in good shape and I was setting up my shack for a higher power transmission. Icon 746 into a 80A with a LDG AT 1000 pro tuner (1 kw) into a Cushcraft A3S 3-element beam (10-15-20m) with a 40 meter add-on. Everything worked beautiful testing 10-40m with the 80a operating on 115v putting out 700-1000 watts depending on the band. The tuner did not have to work hard since the antenna was tuned to these frequencies.
I then tried 80 m and apparently I did not have the antenna tuned properly with the tuner. When I engaged the amp and started to transmit, all hell broke lose and the transmission was very short. After that, the amp would not transmit anything.
I unplugged the amp and took off the cover to look for damage. To make a long story short, the relay contacts were burned (replaced), a couple of diodes were burned on the PO/ALC detector board (all replaced), and the safety choke was smoked (replaced). Put the amp back together and it worked as before on 10-40m. No output on either 80 or 160 m into a dummy load. Looked a little further and 80m contacts on the band selection switch were burned (replaced the whole switch). Amp still only shows output on 10-40 m.
Checked the radio and it puts out RF at 80 m though a little weak. Sent it in and no damage to the radio. Substituted a different radio which has a robust 100 w on 80 into the amp (Icon 706) and still no output. I replaced the pertinant doorknob caps within the 80 m circuit with no effect. I even checked the tuned input components for 80 m but the RF would have to flash back through the tube. No problem found.
Frankly, I am puzzled because I cannot find any component defective on the 80m circuit or I have replaced them all.
Any suggestions or help is requested. The amp acts like no RF is entering the tube on 80 m and the output on 160 m is very small (20 w).
I am new to the forum so I have not figured out if I could post the schematic.
Thanks