My everyday amplifier started showing some signs of needed some attention about a month or so ago. I have been kind of busy and took it out of line and used a back up amp for a while. Curiosity got the better of me so I took the covers off this past weekend to see if I could find out what was ailing it.
This amp is pretty much all factory aside from the two main filter caps being replaced (not by me) at some point in the past. It has 6-6KD6 tubes (maybe original?) in it. I had the cover off of it 1 time since I have owned it (about a year and a half). It has been mainly used behind my TS440 on the "Low" setting. With 60-75 watts input, it showed 450-475 watts output on SSB. It has occasionally been used behind my 139XLR on the "High" setting. With 20 watts input, it showed 550-600 watts output on SSB. All reports were the signal was clean but recently I had reports the audio was "fuzzy" and noticed output was climbing to near 900 watts! Oops, time to shut it down.
Below are a few pictures of what I have found when opening the case.
Clean face. (Not a fan of the plastic toggle switches)
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Underside of RF deck. (No signs of previous work aside from the filter caps)
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You can see the white wire is frayed and has been hot. It was pinched under the edge of the circuit board along with the 2 coax cables-for years! The wire comes from the upper left terminal of the Cinch-Jones plug (total of 3 wires on that terminal) I believe it to be 1 of the 12vac feeds from the transformer which is later rectified and applied to the control grid of the driver tubes.
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I will be working on this in the near future and since it is my "everyday" amp it may get a lot of new parts!
Stay tuned.
73's
David
