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If either one fails to go close enough to zero, the next question would be which one? The mode switch interrupts power to internal sections of the radio when it's turned. A circuit that's on the edge of cutting out can 'catch its breath', so to speak if the power is briefly interrupted. 73

Used the bridge-rectifier trick on 23-channel radios decades ago for a local quarry. The drivers figured out a blown radio was an unscheduled break. The owner didn't care that the voltage drop reduced the radio's transmit power. The bridge-rectifier trick works for anyone who doesn't have a...

The article does point out a remaining competitor in Massachusetts, Kennetron. https://www.kennetron.com/ Honestly never heard of them until now. Econco was it. 73

I should come up with a picture of some sort for this, but for now, find two wire jumpers on the circuit board, to the rear of the meter. J26 and J27 carry the radio's transmit-only and receive-only power feeds to the radio's circuits. They are almost 3/4 inch long, at an angle to the front edge...

Folks accustomed to the design of 40-channel SSB radios since the 1980s will expect the radio's internal carrier frequency to shift up and down to select upper or lower sideband. This is done by making the crystal filter's passband, or "frequency window" more or less symmetrical. A lot of...

Sooner or later oxygen gets into the act. The braid will eventually oxidize where it lays against the connector body's surfaces. Heat from high RF current will only speed up the oxygen chemistry. What should be a low-resistance connection from braid to plug has gradually higher resistance...

People skip soldering the coax braid on their coax jumpers. And for good reason. It's tough to get it hot enough to properly solder the braid to the connector, and not just to itself. But it makes the service life of that jumper short. The braid oxidizes and makes poor contact with the metal...

The black paint obscures ID of DEI transistors. Cracked apart some cadavers and that's what I found inside. The four-die layout of DEI's 2879 copy. Don't know anyone else using such a cornball layout. 73

The resistor is a casualty, not a cause. Just where is it on the circuit board? 73

The combiner that each transistor pair feeds into should have a resistor inside or alongside it. If this resistor is burned, one of the two pairs has dropped power. If I had to guess I'd look at the capacitor connected collector-to-collector on each pair. If one of those takes a hike you'll...

Unhook one end each of D16 and D17. See if L5 exhibits a peak now. L5 has no internal capacitor to go bad. If it won't show even a shallow peak there's a fault of some sort on its input side, most likely. Or maybe the antenna was connected during a storm when a neighbor's tree was stuck? Burned...

A pretty good HD restoration 73

Backwards. Pin 1 is towards the front of the radio, closest to the MB3756. The voltage on the real pin 10, nearest the rear panel, is coming out of the chip pin onto the foil pad. The pad should show zero with the pin lifted. Yeah, pin 10 reads a little low, but color me skeptical. A 'scope is...

Yeah, my idiot light's shining pretty brightly right now. Voltages look okay in the right order. A 'scope would instantly reveal if the audio level is the same on both sides of C179, the fat 330uf cap connected to pin 9. Not a common fault, but on the list of suspects. If it fails open circuit...

May not be "the" issue, but it's an issued. Pin 1 connects directly to the main B+ power coming in to the radio's circuit board. Means the radio is running from under 11 Volts. Needs more than that. 73

The IXYS part looks promising: The Fairchild part has been discontinued. The DigiKey listing is a drop ship from Rochester Electronics. Looks like they'll sell you all 150 in their stock or none. That company's claim to fame is buying up discontinued parts and getting a healthy markup after...

Somebody did the research work I have studiously avoided. Arbitrage is a keystone of capitalism. Find something with a value that exceeds its price. Buy low, sell high, right? Yeah, the secrecy angle is annoying, but somebody figured it out. Feel free to do the same thing. The specs for the...

Good to hear they can still spell "customer service". 73

Just make sure the fans blow onto the heat sink fins. That's where the heat is at. 73

Somebody got sloppy or in a hurry doing data entry. Where do you think those numbers came from? Someone with a keyboard. 73