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Some final/driver transistors have that extra diode inside them. Some don't. After all these decades, I'm still waiting for a proper explanation why. The tester is just shownig you what's there. 73

Have a close look at the filament pins. As in very-bright light and a magnifier. This is the pair of pins closest together. They carry the 15 Amps of filament current and get hot first. The real danger here is damage to the tube socket. The thick wire that passes through the glass base of the...

It was when it was built. Might or might not be now. 73

That resistor is in series with the radio's drive power to the transistors. A pair of MRF455s only needs about ten or twelve watts peak to smack them fairly hard. Even a wimpy AM CB does half-again more or twice that. You'll be hard pressed to find a radio that small. The resistor serves two...

It's an AM-only linear that has a switch marked "SSB" on the front. It's not there because it's useable, it's there because buyers think it should be. This is an old design, built decades ago with a handful of circuit details totally missing. Saved the maker money, and when everybody was using...

Sure makes it sound like there's a 'glitch' resistor that's popped in line with the HV to the anode choke. A DC meter that can safely handle 2000 Volts DC to the plate cap of a tube would reveal this if it's the problem. Zero Volts on the tube plates will get you a pegged-out grid meter. Might...

A 'scope is just a voltmeter with a dot in place of a meter needle. Positive voltage and the dot moves up. Negative input to the probe/vertical channel and the dot goes down. A time base sweeps the dot from left to right at a chosen speed. With any luck your 'scope is new enough to have...

The smaller, burnt resistor is R5, a 5.1k 5 Watt resistor. It's in series with the 12BY7 driver tube's screen grid. When R5 goes open circuit, no transmit. We use a 5k 5 Watt wirewound. No special reason to use a film resistor like the original. The longer resistor alongside it is R37...

This has been our policy for replacing any DIP-package chips for decades. You can reduce the heat stress to the circuit board foils by clipping the pins on the old chip, up against the 'shoulder' of the pin where it meets the plastic. Melting the solder and pulling each pin 16 or more times is...

Found another on the GE Superbase thread: https://www.microchipz.net/vco-units 73

There was an Ebay seller in England selling replacement VCO modules for Cybernet-made CBs. Can't remember the name. The tuning slug in the factory VCO module tends to get cracked and umoveable. I'll see if I have any record of who that was. Found him...

Yep, those are called "K-Tran" IF/RF transformers. They tune with a cup core on the outside of the winding, rather than with a hollow core and a slug on the inside. It was a high-performance part back in the day. The cup core was also a magnetic shield. You could crowd them closer together...

The HV filter caps all look original. Can't make out date codes printed on any of them, but I'm pretty sure that brand "Industrial" has been gone for 40-plus years. 73

Cans? As in slug-tuned IF/RF transformers? Yeah, most of them. T1 doesn't. It relies on C11 to tune it to resonance. The rest of them have at least on internal disc cap. 73

How many of the 10 or 12 electrolytic capacitors have been replaced? If any of them are original, this is trouble in the making even if all of them still work today. Good chance at least one of them is contributing to reduced performance. 73

Whupsie. Much bigger. My bad. Forgot how large that model's transmit power is. 73

Consider that a measurement in steps of 0.01 Volt has an uncertainty more or less equal to this lower limit. A difference that small just isn't significant. The rule for matching is the closer the better. We test a batch of 20 or 50 and mark the last digits on the rear. They get paired up by the...

Was also used as the power/speaker socket for 1970s car stereos. Can't remember what brand. 73

The problem is the amplifier is meant for a single-final radio. You're hitting it with about double what it's meant for. Any radio that has to be turned down below a one-Watt carrier is just too big. Simple, cheap fix is to push in the "AM" button. Should drop the gain enough to accomodate a...

If the mismatch increases with power level increase, two possibilities emerge. Either the amplifier's signal purity suffers as the power increases and it's adding a second frequency not in the band you're tuned for. Or the core of an inductor is saturating past 150 Watts, reducing its...