A Vintage Transistor Radio Gets A Repair

Here in 2023 the field of electronics covers a breathtaking variety of devices and applications, but if we were to go back in time far enough we’d enter an age in which computers were few and far between, and any automated control systems would have been electromechanical at best. Back in the 1950s the semiconductor industry was in relative infancy, and at the consumer end electronics were largely synonymous with radio. [Shango066] brings us a transistor radio from that era, a Jewel TR1 from about 1958, that despite its four-transistor simplicity to our eyes would have been a rare and expensive device when new.

As you’d expect, a transistor radio heading toward its 70th birthday requires a little care to return to its former glory, and while this one is very quiet it does at least work after a fashion. The video below the break is a long one that you might wish to watch at double speed, but it takes us through the now-rare skill of fault-finding and aligning an AM radio receiver. First up are a set of very tired electrolytic capacitors whose replacement restores the volume, and then it’s clear from the lack of stations that the set has a problem at the RF end. We’re treated to the full process of aligning a superhet receiver through the relatively forgiving low-frequency medium of a medium-wave radio. Along the way, he damages one of the IF transformers and has to replace it with a modern equivalent, which we would have concealed under the can from the original.

The video may be long, but it’s worth a look for the vintage parts if not for the quality of radio stations on the air today in California. For many readers, AM broadcast is becoming a thing of the past, so we’re not sure we’ll see this very often.

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Diagnose And Repair A Yaesu FT-7800 Ham Radio

Yaesu FT-7800 Ham Radio

[Alan Wolke] aka [w2aew] was challenged to repair a friends Yaesu FT-7800 ham radio. This radio operates on two ham bands, 2 m VHF and 70 cm UHF. The complaint was that the 2 m side was not working but the 70 cm was transmitting fine. Alan started by verifying the complaint using a Bird watt meter with a 50 watt slug and terminating the signal into a 50 W dummy load. [Allen’s] bird meter is the type that has an RF sampler that can be connected to an oscilloscope for added signal viewing and validation.

After verifying that the radio was not working as described, Alan starts by glancing over the circuit board to look for any obvious damage. He then walks us through a block diagram as well as a circuit diagram of the FT-7800 radio before stepping us through the troubleshooting and diagnostics of radio repair. Even when he realizes he might have found the problem he still steps us through the remainder of his diagnostics. The skills and knowledge that Alan shares is extremely valuable to anybody looking to repair radios.

Spoiler alert. At the end of the first video he determines that the pin diodes near the final VHF output were bad. In the second video he reveals that he could no longer source these bad components. Through some clever evaluation of a more current Yaesu radio, [Allen] was able to find suitable replacement components. Lesson two ends with some surface mount solder rework tips as well as testing that the repair was successful.

And just in case you don’t know what a pin diode is, or is used for, Alan shares a third video covering just what this component is and does in a radio. You can follow the jump to watch all three videos.

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