Archive for the ‘Radio, Television entertainment’ Category:

2019-11-27 “Oscilator Colpitts” Doesn’t!

I found this schematic on a website and it’s recognizable because the author misspelled it oscilator – he left out one of the Ls (I corrected it on my copy). So I built it as shown but it wouldn’t oscillate. The values of base bias resistors R1 and R2 gave a saturated transistor. I had

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2019-11-26 My Radio As A Kid

from FB Comment Nov 26 I inherited old tube radios, I never had a boy’s radio, still don’t today. But I got a 2 transistor SupereX kit that I built. It was a crystal set with an earphone amplifier. Didn’t work very good because I lived a few miles from an AM transmitter and until

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2019-11-16 Fixing a Driver Transformer With An Open Primary

Also FB group Building Transistor Radios 2019-11-16 I was working on a Realtone 10 transistor AM radio that had a driver transformer with an open primary. I slit open the wrap and found the tiny fine wire on the right was loose so I soldered it to the heavy wire. But it was still open.

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2019-10-12 RF Oscillator Won’t Make A Sine Wave, Only Sawtooth

I wanted to make an RF Oscillator that puts out a sinewave at about 734 kHz, which uses two convenient values, 100 uH coil and 470 pF capacitor. I used the toroid core with 16 turns of 30 AWG wire, with a tap at 4 turns then later 8 turns. I built the circuit in

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2019-10-07 Zenith Royal 500H Troubleshooting

I got this from eBay, it doesn’t make any sound at all. It has a small crack in one corner but the case is otherwise okay. The screw on the bottom is corroded but the battery holder is in halfway decent shape. It needs a bit of cleaning, the metal is a bit tarnished but

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2019-10-05 Huge Corcom Filters For RFI

from FB group post to Building Transistor Radios 2019 Oct 5 I spent quite a bit of time adding filtering to my 0 to 30VDC, 10A SMPS to get rid of the RF interference. It was successful, I got rid of most of it, but not all. So I think I found the solution. This

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2019-09-09 Zenith Royal 475 Information

more text below Zenith Royal 475 ARF project & service info links: https://antiqueradios.com/forums/viewtopic.php?f=4&t=233319 https://www.antiqueradios.com/forums/viewtopic.php?f=4&t=226370 https://www.antiqueradios.com/forums/viewtopic.php?f=4&t=235052 The Zenith factory schematic and PCB layout is located on page 185 of the Beitmans service literature which is freely available on-line: https://www.americanradiohistory.com/Archive-Rider/BEITMAN-SUPREME/Beitman-1961.pdf ** also posted to FB group vintage transistor radios Usually the capacitors are the problem. There are

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2019-06-12 Plug-in Coils Pros And Cons

from FB group Regenerative Radio… Jun 13 I’ve thought about using plug-in coils, but I’ve had experience with Grid dip meters and there are a few important issues that must be dealt with. One is, what happens to the unused coils when the equipment is not in use. They get separated from the equipment and

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2019-06-11 Selenium Rectifier Burned Up, How To Replace

from FB group Vintage Transistor Radios Jun 12 Bob Kirsch has the right idea, but the single replacement diode *must* be rated for 400 V peak inverse voltage or more. A 1N4007 is cheap and readily available. I assume you’re in a country where the AC line voltage is 120 VAC, because the rectified DC

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2019-05-31 DIY Plastic Variable Capacitor

I hear others complain about the high cost of variable capacitors, especially the older air variables with metal plates. So I decided to DIY and make one. This is my first attempt so forgive the lack of elegance and unfinished look. I’m sure it could be improved on and made better with some effort. The

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