Friday, April 19, 2013

BREADBOARD POWER SUPPLY

     One of two identical units needed for the ARRL rig in "Building an Amateur Radiotelephone Transmitter" and a nice example of later breadboard construction.  Mine follows the original as closely as I could manage, with the addition of a fuse and front-panel switch.
     Still dangerous, despite a smear of white paint on the neutral side of the AC plug so you can get it in the socket right way round and a ground terminal connected to the shells of the transformer and choke to hook to station ground.  Making it child- and pet-safe can be done but you'd need some ingenuity, especially if maintaining a period look is a goal.

     This one checked out at over 500V with a capacitor-input filter -- those 630 Volt Solen Fast filter condensers suddenly don't seem all that extravagant!  I changed to choke-input (look closely and you can tell) and the output is still too high for the application: the transformer dates to before Hammond changing to a tapped 115-125VAC primary and the HV secondary was high-ish to start with.  So it'll have to be replaced by the next step down.  Good thing I hadn't built both of them.

     Too bad I'd already bought two transformers.  Hey, extras for the next project -- might even be big enough for the Harvey-Wells Bandmaster power supply that needs built.

4 comments:

  1. That is very nice looking work! Soldering I can do. Wood I cannot.

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  2. Wood just has a different set of rule -- mostly "measure twice, cut once, keep doing it until things are right." For most of us, the ratio of setup time to cutting/assembling time is -- and needs to be -- ridiculous -- 5:1 or more. And that is very, very hard to do, or at least it is for me.

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  3. Lovely work this. I just discovered and signed up to follow your blog. I'm a ham interested in mid-century CW gear. -- Ken, K3VV

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