Archive for March, 2010


March 2nd, 2010

One of my TS-930s (2-million S/N) has always been a little touchy when it comes to the synthesizer PLLs. A while back, I put new electrolytic capacitors in the power supply because the old ones were drying out, reducing the regulation. After setting the supply voltage back to 28.5 volts, I noticed the PLL wouldn’t lock (indicated by the letters PL.L on the display—this radio has the PIEXX digital board upgrade) on any band.

Thanks to KA5IPF, whose expertise has been invaluable to me as a Kenwood owner, I learned that this was probably due to the master heterodyne oscillator not oscillating since it affected all bands. I tweaked L77 on the signal unit (front corner of the radio behind the PITCH/AF TUNE knob) until the oscillator dropped out, then backed up until it came back and dropped again. Then, I split the difference, just as Clif recommended. I had the radio on 40 CW at the time. And, it was so touchy that when I changed bands, it would unlock again. So, I got it dialed in on 40 CW and left it. This was fine since I was operating domestic contests at the time and having a radio on 40 all the time from the Midwest is usually a good idea.

But, now that I’ve moved to the East Coast where DX contests are the name of the game, I’ve decided that it would be a good idea if the radio were more frequency-agile. I pulled it apart last night and got to the PLL board, which is notorious for cold solder joints. (Is it a bad thing when you “just know” how to get to any circuit in your radio in 10 minutes or less? Probably.) I didn’t see anything that looked visibly cold, but I went around and reflowed a bunch of joints and, fresh off my success with the TS-700, I cleaned all the connectors. Then, I repeated the L77 master heterodyne oscillator adjustment.

It seems to be working now, although I need to give it a good run in a contest to be sure. This leaves only the radio that eats expensive transistors like popcorn to be repaired…


March 2nd, 2010

Saw a talk by John C. Knight of the University of Virginia yesterday:  The Use of Rigorous Arguments in Engineering.  Basically, instead of employing standards to ensure interoperability and reliability of complex systems, he proposes using a (tree-like) structure of justifications that is specific to the project.   These two statements remained with me:

An argument without evidence is unfounded.

Evidence without an argument is unexplained.

Although it sounds obvious, we engineers and scientists occasionally forget these principles in the rush to write-up our work.