Archive for the ‘AM Band’ Category:

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

Also FB group Building Transistor Radios 2019-11-16 I was working on an 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. ☹️😱 So I

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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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2019-05-31 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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2019-05-29 Another Oscillator For AM Band

Also posted part to FB group Building Transistor Radios May 30 I built this coil by winding 20 turns 28 AWG enamel coated wire on a soda bottle cap. It has an inductance of about 17 microhenrys. I wound a tap for the antenna, but it would be more stable if a separate coil with

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2019-05-05 Using a 7805 For An Adjustable Regulator

from FB group Building Transistor Radios Willie Barnett When you understand how the 3 terminal regulators work, you can replace the 1N4148 and the almost impossible to get 1N34 with just a pair of resistors. The 7805 or 78L05 regulator always has a fixed voltage of 5V between the O and G pins. So you

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2019-04-05

from FB group Vintage Transistor Radios April 6 I clicked on the link and I looked at the schematic. I’m surprised that in 1959 they had a radio that used the OTL amplifier to drive the spkr. I remember OTL was used in the early ’60s for Hi Fi amps, but I didn’t think that

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