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Might want to consider the ambient temperature, especially if it goes into a tube-type radio. It's all about temperature rise, after all. 73

I think it's the "EPT we didn't print a schematic" board. Pretty sure I have some pics at work that catch the number. We'll see. 73

Just when you think you've seen everything. Found a bad final transistor in a RCI2990DX. There was no heat sink compound between the ceramic insulating washer and the heat sink. But the washer was glued to the transistor with white bathtub caulk. I guess somebody told the weekend warrior to...

Shouldn't overburden the 8 or 9-Volt regulator in modern radios. An older radio that uses just a zener diode and ballast resistor will need to have that resistor removed and a 7808 or 7809 regulator put in its place. Or simply adding a regulator just to power the BR would be less trouble. The...

Seen Thunderbolt models with the stainless face, but not this one. The two band select switches suggest they were trying to jump through the same loophole in the rules that Palomar and D&A did, pretending to be a ham linear. If it has one 6LQ6 tube driving three it may be very close to the...

The 600-Watt rating is a total fraud. Looks like it will be working hard at 60 Watts. 73

RM Italy's AD203, "stinger" module looks like a good deal. Until the day it goes poof. This one is in a DAK mark X cabinet alongside a Taiwan Cobra 148 and suitable power supplies. The stinger's heat-sink plate is bolted to the rear panel of the cabinet. There's a standby switch that revealed...

Lou Franklin tells us that this chip came from four different vendors, each with its own type number. Motorola was the original developer and called it MC145104. National Semiconductor called theirs the MM55104 Panasonic MN6040A And finally Nucleaonic Products Inc. (NPC) called it SM5104...

Well look on the bright side. You trained it for free. 73

Now for the rest of the story. The front-panel band selector has been reconfigured for three tunable bands. The original crystals get removed if that's where they were found. We left off at V3. Either a single crystal gets removed from there, or you'll find a long solid wire that leads from V2...

I do remember seeing a disc cap on pin 3 of the mike socket that would do this. Changed it from a .01 or .02, whatever it was to a .001. Fixed the issue. Taking the pin 3 wire loose from the from the socket would reveal if the socket is involved. And if taking the wire loose doesn't change it...

Adding a second or third tuneable receive band to the *original* version of the Browning Golden Eagle Mark 3 receiver requires bypassing the factory circuits meant for receiving a fixed frequency using a 4 (or so) Mhz crystal. This was to use it as a business radio. Your plumbing trucks would...

Had a paper copy back in the day. Haven't seen that model in decades. Was popular when Copper was selling it in the 90s. I'll see if I can turn it up. Our paper library has suffered severe neglect since putting day-to-day schematics on computers. I have no recollection of how "J36" applies to...

So just what problem are we correcting here? Zener diodes are known to fail, but if a new one didn't correct the issue, it's being caused by something else. A new zener got tested at the factory. Shouldn't be bad out of the package. What's the issue? 73

Congratulations! Gotta love it when a plan comes together. 73

Good to hear Don is still around. Got me out of a few jams with parts nobody else had back in the day. Kinda lost track when the market for RCI parts opened up. 73

I'll admit to being baffled. Turns out there is no Sams CB volume that covers this one. The PLL01A chip says it needs a 10.24 MHz reference input. Pin 4 selects divide by two to the tenth (1024) when high. The schematic shows no connection. Makes it appear the pin is internally pulled up to a...

Wow! They upgraded to surface mount. The pink (violet?) wire is power, the black wire is ground. Leaves you three white wires. One of them is the audio output. The other two probably connect to a pushbutton switch. One white wire is attached near the board's edge near the black wire. I'll guess...

Took a couple of days off. That chip didn't show up in radios I remember from the 70s. Honestly don't recall modding a radio with that one in it. The only schemo I have here at home shows a PLL02A for that radio. I'll see what the Sams shows next time I get to work. 73