Archive for January, 2020:

2020-01-18 More Zenith Royal 200 Conversion to Silicon

Continued from post 2020-01-15 I dug through my drawers and boxes of transistors and found a bunch of MPSA56 PNP general purpose on tape, and put them into the LO and mixer. I think they helped slightly – they are lower minimum fT than the 2N3906s. I adjusted – optimized – the trimpots I had

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2020-01-16 How To Remove Battery Corrosion

I took a battery holder that was corroded by leaking alkaline cells and I put it in a cup of vinegar. After several hours it came out clean, and I washed it off and let it dry. It looks pretty good now.

2019-01-15 Zenith Royal 200 Conversion to Silicon

My Zenith Royal 200 conversion to silicon transistors is going slowly. Right now I’m working on getting a good sine wave out of the local oscillator (see photo). The waveform had high frequency parasitic ringing every other cycle. I put a 100 ohm resistor in series with the collector lead and it helped some. I

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2020-01-13 Slide Rule and Calculator Battery

From FB group Jan 19 Joe Haupt In the ’80s I occasionally did work in an electrical room on campus that had a 7 foot slide rule that had been removed from the classroom. It was there for years, but the fire inspectors would make us keep the junk from accumulating in closets, so it

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2020-01-11 Reinventing the Archer’s Bow – Amazing!

So why didn’t someone think of this long, long ago?  It has so many advantages.  It’s amazing!

2020-01-10 Corrosion and Damage On Diode Leads

This photo is a detector diode that was broken during replacing the electrolytic capacitors.  The lead on the top was twisted, apparently putting stress on the glass package.  I replaced it with a 1N270 germanium diode. comment from fb group Vintage Transistor Radios Did you notice that the leads are magnetic? They stick to the

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2020-01-08 Sorting Transistors Compared to Picking Fruit

I started thinking about how the makers of transistors sort the different grades of transistors as they’re manufactured. I thought that a reasonable analogy would be similar to how a farmer might sort the fruit he harvests. Here’s what I came up with.The farmer starts with the fruit his workers have gathered.  The fruit is

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2020-01-06 Two Similar Transistor Radios

I posted this a few days ago.https://m.facebook.com/groups/606087512820068?view=permalink&id=2638214152940717 Now I’ve replaced the capacitors in another one very similar, a DE LUXE. It’s not quite as complete and in as good a shape as the Encore. What surprised me was that some of the electrolytic capacitors were bad (measured open) and the symptom was no sound whatsoever

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2020-01-02 Coax Cable and Crimp-On Connectors

FB comment Years ago at work (community college) we had an IBM mainframe and the terminals were connected with coax cables. We also had thin Ethernet cabling. I had the proper connectors and thousand foot boxes of coax, and most importantly the proper stripping and crimping tools. I installed hundreds of coaxes, and I was

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2020-01-01 VA3IUL Website RF Projects

I spent too much time looking at the schematics and projects at this website.  Lots of interesting things to download.https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Homebrew_RF_Circuit_Design_Ideas.htm

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