Archive for the ‘Receiver’ Category:

2020-05-28 Solid State Shortwave RF Preselector

Comment left 2020 May 29 on YouTube video in the title. This video covers MOSFET, dual gate MOSFET, JFET and BJT tuned preamps (preselectors) for his shortwave crystal radio. “The talk about using 18 volts for the cascode got me thinking about tube designs. When the plates need 100+V, and when the heater to cathode

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2020-05-22 PIM Passive InterModulation Explained

Good article on passive intermodulation, AKA the Rusty Bolt Effect.

2020-03-31 Collecting Novelty Transistor Radios

Also FB group Vintage Transistor Radios Collecting novelty transistor radios has a few drawbacks, the most obvious is that they are much rarer than regular transistor radios. Generally the new novelty transistor radios are much more expensive then a regular radio due to their limited production. The customer who just wants a radio is going

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2020-02-19 Nobility 15 transistor Radio Repair

2020 Feb 18 – Nobility 15 transistors OTL S/N (?J)29549 I replaced the electrolytic capacitors. The spkr buzzed when I touched the volume control. Nothing from the detector (transistor). It’s unusual. I pulled and tested some IF parts including one of the transistors, no problems found – transistor tested good. I called it a night.

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2020-02-17 I Bid On A Boy’s Radio, Lost

From FB group Vintage Transistor Radios Last week I bid on a boy’s radio, $26 which lasted up until near the end. But as usual I was outbid at the last minute. I think the demand exceeds the supply, and the prices go up too high. Looks like I’ll be getting one that no one

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2020-02-14 Zenith Royal 400 S/N Z551549 Replaced Capacitors, Driver Transformer

Zenith Royal 400 s/n Z551549 I soldered broken orange wire to battery holder. Replaced all four electrolytic capacitors. Silent speaker and nothing from earphone jack. I checked the voltage at the collector of the driver transistor, it was zero. One pin of the driver transformer primary measures 5.8 V, the other pin measured 0. Checked,

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2020-02-06 Royal 500H Alignment

From FB group This Zenith Royal 500H radio has the extra 8th transistor for the RF amplifier, so it should have excellent sensitivity and be able to pick up those weak stations. Most of the problems with old radios are with the electrolytic capacitors, but the Zeniths all use the carbon composition resistors and they

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2020-01-30 Royal 200 Silicon Conversion, Part 3

Also to FB group Vintage Transistor Radios I finally drew the line and said I’m finished fiddling with this Zenith Royal 200 and put it back together. I got it without knobs or handle, and with all the transistors missing. It’s not pretty, and the speaker cone is warped and sounds bad. This is the

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2020-01-20 Costs of Radio Assemblies and Parts

From FB group Vintage Transistor Radios A thought occured. Do you think that Motorola may have had a lot of parts for tube sets and they decided to use them up by putting a transistor chassis in them? If you break down a radio into its assemblies and/or parts, which of them has the highest

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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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