The project is complete!

Today I powered up the amp and made a contact on 20 meters SSB. I'm showing somewhere between 500 and 600 watts output. That is the end of the story. But here is a little more about how I got here.

The capacitors came in, from Digi-Key. I was able to order the exact replacement part number (from CDE) as the ones originally installed in the amp. Also, the 811's came in from Tube Depot, very carefully packed and all in perfect working order. And my Variac came in, from Amazon, and I hooked it up and measured the output using my Kill-a-Watt plug-in device. The voltage on the knob seems to be off by as much as 10-15% of the indicated reading. That's not a huge deal, but worth knowing.

So all of these replacement parts got here at different times during this past week. I just kept them in quarantine while waiting for the rest of stuff to get here. (I've been doing that for most stuff that I buy mail order - when it gets here, I set it in a remote place, and just walk around it for a day or so, for the cooties to die.)

Also, one of the things that I needed to change, so that I could use this amplifier, was to upgrade my antenna situation. I have a 20-meter double bazooka antenna which is rated for high power, but the feed line I was using was RG8-X or maybe even RG-58. It was actually two pieces with a barrel connector, since it was just a "temporary" setup while I fixed and remounted my vertical. But that vertical (actually the balun in the matchbox at the base of it) can't take more than 100 watts, so it's not a candidate for use with high power.

So I ordered and received some coax cable, and soldered a couple of PL-259 connectors to it after cutting it for the right length. And the "right length" has changed, as before, I had mounted the antenna over my metal roof, but now have that stretched between two trees. So I got some height, and I got it away from metal. And the new location is virtually invisible from the street, so my place looks a lot less full of wires and antennas - for the neighbors. (Hat tip to MPD Digital, www.usacoax.com who sold me the cable, and it was quick and perfect!)

So today was busy - after a planning meeting with K8OD and WG0Y, about Winter Field Day 2021 (we had a Zoom meeting with the club and K4HOG gang), I came back home to move the antenna, which was of course, actually taking it down and raising it, so it was really two things, not just one. Lots of up and down on the ladder and slingshotting into the tree, etc., all that antenna raising stuff. (This time I did NOT leave any fishing weights in the tree branches, so I must be getting better at this!)

After the antenna was up and tested, and the coax replaced, I tuned through the band. Also, I checked the SWR and it looks like the resonance point has moved a little. But this antenna is under 1.5:1 across the entire 20-m band. So it's all good.

I still had a lot of the day left so I figured I would attack the amplifier. I replaced the capacitors, and replaced the tubes, and put it back together enough to engage the safety interlock. I powered it up at low voltage, and nothing bad happened. (I also found out that the Kill-a-Watt doesn't operate unless you get the line voltage to around 75-80 volts. It still passes through everything, but the metering doesn't display anything until that threshhold.)

After a while, I went to full voltage, and things were still good.

So the RF cabling needs to be addressed, with high power, since I am now going from the radio, through the wattmeter/SWR meter, to the amp, out the amp and into the antenna tuner/SWR/dummy load box, and then out to the antenna. Everywhere after the amp needs to be good cable that can take power.

The first one I tried, a short pre-made section of 9913, gave me infinite SWR (with the amp in standby). I assumed that maybe the relay inside had a bad contact, but it was easier to switch that cable and see if the problem changes -- it did. Now everything plays nice, and I started bringing up the amplifier. At this point, I'm just following the instructions as if it were a new amp, so after downloading the manual from the MFJ site, I went through that step-by-step and it all worked as it should.

I made a few test transmissions, and then went outside to see if I set anything on fire (only kidding a little) and as timing would have it, K8OD was passing by, so I had to tell him all about my day! (Remember I was at his place earlier in the day, yet all of this was new since then!)

I left the amp powered up in standby for three hours while I sat nearby doing various stuff, just to watch it (and within sniff distance too) in case anything went wrong.

So I am convinced that it's as good as new and ready to use! The inside was in new condition, and the outer case is almost new condition, but a few scratches and some "footprints" from whatever I had sitting on it in years past.

So I will probably use it about as much as I used to, that is, only when I can't get through barefoot. My bazooka really works well, although only for one band, and whatever other antennas I end up using, for the other bands, I'll just be sure that they can take some high power.

Ultimate I'm going to put up a doublet, maybe 130' and fed with ladder line, which can take plenty of power. That actually might make sense to have that up in time to use it for WFD.

But for now, I am just savoring the results of this simple change to the antenna, and also knowing that I can QRO if I need to. I'm going to get on 20 CW in the morning and see what the gray line gives me.

Thanks for following along on this story. If you have any comments or questions, feel free to comment on any of the postings where I have told this story.

73, and see you on the air,
Dave
KZ1O

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