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Google is your friend. On a good day, at least. Only offered me one source today...

Tough to troubleshoot without a schematic. 73

Motorola data sheet from RF Parts. Says it's a MRF454 selected for performance measurements. 73

A display that won't clear itself before showing a sign-on "hello" probably has a hardware problem, not a firmware fault. One reason I stopped repairing hand-held electronics years ago was because most repair problems are caused by being dropped. I'll guess there's a mechanical failure somewhere...

Bear in mind that you're correcting boo-boos in the original 1970s design. Not a lot of attention was being paid to the amplifier's input impedance back then. You'll want to put a SWR meter and extra coax jumper between the radio and the amplifier's input jack. If the reading is much over 2 to 1...

Seems like the present takes up more and more of my time to cope with it. The future gets less and less attention, seems like. No apprentices in these parts. The occasional curious young person comes around. I just tell them I'm a hardware dinosaur waiting for the asteroid. 73

Opened in 1969? Got me beat by six years. Has to be really old by now. I wish his comeback all the luck in the world. Personal experience with folks in this sort of spot hasn't gone well, for the most part. 73

Cool! Welcome back. 73

Gotta take one leg loose to check the bias diode. The circuit resistance in parallel is too low to obtain a meaningful test of the diode in-circuit. Just won't work. 73

No, the solder adheres to a thin electroplated layer of nickel. The solid pin that comes through the glass is a tungsten alloy chosen to have a tempco of expansion that matches that of the glass. If either the pin or the glass were to expand faster than the other with heat, the glass-to-metal...

It should. For a while at least. It's kinda old, and may suffer from electrolytic cap disease if it has a lot of miles on it. Unless someone has been doing preventative maintenance there's a good chance one or more rotary controls will be 'scratchy' and need a taste of control cleaner. Probes...

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...