Homebrewing

Homebrewing is a lot of fun. And you do not have to possess a MA in Electronics to put it to good use,
A while back I was thinking seriously about buying a CT-17 from Icom. This is an interface to connect a PC to up to 4 Icom radios, it cost 140 dollars or so for a new one, and on the used market you see them from 70 to 90 dollars. While daydreaming of one, I downloaded the manual and began to read, the schematic was interesting, it was basically just a MAX232 chip and its associated circuitry, I hurried to the Mouser web site, totaled the parts were only 14 dollars and that included shipping!!! I ordered and received the parts in short order, this is the result


The little box on top is the homebrewed CT17, works in fact better than the original as one fellow ham pointed out that the output from the MAX232 was not buffered and in fact under certain conditions could result in radio damage, I added a buffering IC to take care of this for a whopping 1 dollar addition.
Below is the Winkey2 Serial that was built from a kit, anther wonderful toy at only 36 dollars it beats any keyer out there!

Fixin a broke power supply
Like a lot of hams, I thought that just because I had gotten some decent up time on my Astron power supplies that they were "bulletproof", nothing could be further from the truth. Over the years I had noticed some knowledgeable hams making somewhat negative remarks about the Astrons but I dismissed that as people who never had taken the time to own one. Then one day early this year I decided the current hungry 756 Pro II needed something a little more potent than the skimpy 20A supply I was using. I put a WTB ad out and within a day or so I had a selection to choose from. One in particular was from a well-known ham who sold a lot of gear. It was from an estate sale and the price was right. So off went a money order and in a couple of days I had my new 35A metered Astron. The first sign of trouble was when I fired it up and found that with 100 watts continuous output the current meter on the PS showed only 10 amps. The manual states the rig draws 23 amps at full output. I decided to live with that little quirk since otherwise the power supply seemed OK. OK that is until about 2 months later when during a contest I QSYed to 15 meters and upon keying the rig the whole thing died as dead as disco. I thought at first that this surely had to be RF related as the rig worked fine on 20 meters. And it seemed to work fine into my dummy load. But try as I might, the problem was never solved. Then I decided to connect my old 20 amp supply to the 756 and see what happened. Voila, success! No problems whatsoever. Then in the midst of my searching, I found the Repeater Builders website And I found the real facts on Astron power supplies. I had pass transistors failing in mine. The first clue was the low current reading. The meter doesn't read true current, it measures the voltage drop on the pass transistors and if anything is amiss it will not be correct. Again Mouser to the rescue, I ordered 4 of the 2N5302 transistors which are 50 watts heavier each than the stock 2N3771's and I picked 1 50 Amp continuous rectifier to replaced the dual 35 rectifiers that Astron had wired in, while on this I also added an external fan bolted to the heatsink that I robbed from an old PC power supply. Now I have the best power supply I have owned in 30 years of hamming. At the end of CQWW RTTY during the longest and heaviest-duty operation one could imagine, my heat sink was only lukewarm to the touch, without the fan you would have been able to fry eggs on it! Also after replacing the pass transistors my current not reads about 22.75 amps, not too bad 23 is what the manuals states.



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