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A long key down could have compromised C148 and/or C149. All the final's RF current goes through C149. Makes it a candidate for heat damage. 73

Use the fattest silver mica cap you can find. If it's old enough to have a ceramic disc cap, it's time for an upgrade.

That's an old military-type part number. The "251" at the end means 250 ohms. As in "red-green-brown" if it were a fixed resistor with color bands. 73

Here is the web site for Hua Gao the "HG" folks. It's in chinese, so you'll need to click the 'english' button to read it. https://www.hgsemi.com/ Nothing there about buying. Like going to the Ford factory to buy an Escort. They only sell to dealers. The only trustworthy source I know besides...

Next question. Do any of the slugs in the four transmit coils show a peak with the top of the slug DEAD EVEN with the rim of the hole? A coil that's behaving properly and giving you a proper resonant peak will have one peak with the slug below the rim, and a second peak with the slug protruding...

The 26LX6 is probably okay for the driver. For my money the 30KD6 is the best choice. Finding sweep tubes is like finding original dealer parts for a 50 year-old car. They haven't all gone to the dump, but as every year goes by you have to turn over more rocks to find what you need. 73

Update: Turns out the 1981 edition is posted online at the World Radio History site. https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Technology-General/The-Screwdriver-Expert's-Guide-Franklin-1981.pdf It has been updated a few times in the last 44 years, but at least this one is...

I was gonna recommend the best book on the subject, but the author/publisher's web site has gone blank. "The Screwdriver's guide to undertanding and repairing CB radios" is the best intro there ever has been. Lou Franklin's writing style is breezy and understandable. Here's a link to a copy for...

Circuit board is type EPT069611Z most likely. Used in more than one FCC-legal 40-channel radio. The Siemens "S042P" transmit-mixer chip has a new name. Now made by ST Micro, it's TDA6130. Same part new name only. What kind of probe? A unshielded wire from a DMM? Or the tip of a 'scope probe...

Like P.T. Barnum said. "There's a sucker born every minute". 73

The clock/counter in the 1978 Cobra 2000GTL had a design boo-boo in it. They connected the output from an analog chip into the input of a digital chip. Turned out not to be too reliable. Enter Technical Service Bulletin 1232. It shows how to fix this tiny flaw with one disc capacitor and two...

More than one way to make a tube amp unstable. Maco did it by feeding the output energy from the front panel to the rear through coax that had the shield braid not connected. Turned the shield into an antenna, feeding unwanted feedback into the input circuits. An amplifier that's on the verge of...

The 2312 in the pic is not a Mitsubishi product. The driver to its left is. The difference is the width. Mitsubishi made the 2166, 1969 and 2312 9 mm wide. The width for most TO-220 transistor that look like those is 10 mm. A transistor with those numbers that is 10 mm wide is either a HuaGao or...

The old control should have some markings that reveal its resistance rating. Typically three digits in the same format as the three color bands on a fixed resistor. A 250 ohm part would be "251". A 100-ohm would be "101". The letter "B" either before or after the three digits indicates a...

Far as I know, Brian is an RF engineer by training. But some of the things he does baffle me from time to time. The stuff he ships that I've seen is legit. 73

That's a good view of the side opposite the burned resistors. Something is feeding juice into them. Sure don't know what. 73

Any chance there's an excessively-tall solder bump on the bottom surface of the pc board? That could create a short to ground against the heat sink surface. There should be no current through those resistors beyond the radio's drive RF. 73

Are you quite certain this chip is bad? It's probably the single most-reliable part in the Uniden 40-channel and RCI-made radios . RCI was using a tiny surface-mount pc board with pins to match the old chip and a TDA6130 smt mixer chip on it once supplies of the original part dried up for...

Added bias? Where? The center tap of the input transformer has a RF choke on it, with the other end grounded. Won't put any bias voltage on the transistor base leads that way. The resistors that burned appear to be in line with the radio drive power. A failed transistor tends to short internally...

Until I see a schematic that's all they are. Just another flavor of secret sauce. Ideally the radio's RMS power at full modulation should be the same regardless of carrier setting. It's all about the waveform. If you smoosh the positive peaks this raises the average power but hoses your audio...