Monday, September 24, 2012

Project Clean Up Part 1: Chapter 5

Chapter Five: "Ecstasy and Agony"


This is a continuation, the First part is Here,  a complete list is available under "Ham Radio Master links" on the sidebar.

Good news, I made my first QSO with the Twin tube 80!

Bad news, won't be making another one any time soon!

Yay smoke!

In Chronological order, the good news first:
I made my first QSO with this rig!
Yep, it's true, actually made my first two QSO's, one with W1PID in New Hampshire, and one with AK4O down the road from me in Tampa. I got so excited, that I forgot to video the QSO w/ W1PID, even though that was my intention. Here is a vid from right after the QSO,
I felt pretty good about it!
About three hours before 9pm (local time, 0100 UTC), I announced that I would be QRV at 0100 UTC on the QRP-L reflector, the NoGA yahoo group, and other places. About 20 minutes before starting, I went out to the shack, turned on the RX rig, and plugged in the TT80, I noticed a lil' spark right as I plugged it in, looking back I think this was the beginning of the end of the capacitors in this iteration of the power supply. At the time, I didn't think anything about it because hey, tubes were glowin', and there was no smoke!
After getting some of the kids in bed, and tucked in for the night, it was radio operating time. I started calling CQ, and it seemed like almost immediately, I got a return, notably, from W1PID, click his call sign and read his adventures, they are well worth it! He takes his radios all over the place :) Considering my antenna on 80m is a W3EDP with the counterpoise unhooked (is just over 1/4 wave on 80m), and worked against my station ground, I'm glad to have worked anyone, but feel especially good that my signal made it all the way to New Hampshire!
I then took to calling CQ again. Avoiding static crashes, and other QRN, and the ever present Digi QRM, it wasn't easy, especially using the Swan as a receiver. It says "CW" on the mode selector switch, but this is a lie :) it's really the USB SSB filter working, so you hear 2.7KHz of bandwidth all at once. I've had some success using an active audio filter, but I've got a lot of work to do in the shack before I get that particular aspect of the problem solved. I have seen people homebrew CW filters to install in the Swan 100MX, but I don't know if I will yet or not.
About 20 minutes after the first QSO, I copied and replied to AK4O who lives about 36 miles from me (as the signal flies), and also got a nice email from him. I called CQ some more after that, for about an hour, without any luck.
Then, I unplugged the TT80, and tuned around some with the Swan, on 80 and 40, and decided to start trying different tubes (same type) in the sockets. you know what they say about not messin' with a good thing?





And Then:
















EGADS!
Whatever went on in there, wasn't good.
hmmm,
since the first thing I did was change out a tube, I checked the tube base, and I didn't see any obvious shorts, so I began to suspect the capacitor. I remembered the extra beefy spark when I first plugged in the power supply, and I knew I had a suspect!





I found pieces of the rectifier diode, and cleaned up the box and filament transformer with simple green. That's some awesome cleaner. Then I decided to function check the filament transformer. It passed. I tested the resistance across the power surge resistor between the two capacitors: it failed. No continuity!
I then rewired up a new power supply using my last 470 microfarad 250v rated electrolytic, and a new 220 microfarad 250v electrolytic. I went to a 50ohm 10watt power surge resistor (it was as close as Radio Shack could get). Now I am ready to test things out before hooking the TT80 back up. I'm just looking for 150V dc power. Whelp, as soon as I plugged it in the 470 microfarad blew up again.
dang.
I'm throwing this cord out, grabbing another, and trying to scrounge up a couple more caps.
Until then, this project is officially on hold!

Click here to read Chapter 6: "After Action Report and Rebuild Plans"
73,

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