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The 148GTL isn't just one radio, it's a whole product line covering 40-plus years. Much like motor vehicles the internal layout, wire colors and design change over the decades. Not every year like automotive models, but a 1979 Cobra 148GTL is very different on the inside from a 2009 model...
The old "100-Watt bulb in series" test will work. If you get the phase backwards, the transformer becomes a low-value resistor and the bulb will be bright when power is applied. The bulb limits current to a safe value.
And if you get the phase correct between the two secondaries the bulb will...
Are you absolutely, positively sure that none of the new electrolytic caps are installed with the polarity backwards?
When that happens, the capacitor will usually break down internally and become a dead short. A resistor feeding into that capacitor will smoke after the capacitor fails.
Back...
Best clue for a "carrier" on sideband transmit is a frequency counter inline with the radio's coax. If your sideband carrier is stable, and on the channel frequency the fault is probably with the balanced modulator board. If the frequency is unstable, and not really near the selected channel...
It's a frankenradio, alright.
The PB208 should be a big performance improvement over the Malaysia pc board that this radio came with. Really looks like the front panel and counter module got grafted onto the Uniden main pc board/chassis.
73
Gotta wonder how much the temperature of the tube's exhaust air will drop between the tube and the temp sensor.
I'd figure 110 C air sounds like a safe zone. But the surfaces of the tube are bound to be hotter than the air passing over them. Just don't know how much.
Any idea what volume of...
Like this?
https://www.ebay.com/itm/116094116631?mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5336136228&customid=&toolid=10001&mkevt=1
We also have a relay that installs in a CB or "10-meter" radio to key an external amplifier.
My advice is that the higher the drive level, the more...
IT (was) ALAYEEEV!
For about a dozen keys of the mike, and one of the 1976-made 8950 tubes flashed and died.
Forever.
The owner says he has some tubes, so we'll pick up where I left off once he drops them off.
I'm about ready to call this "Maco Syndrome". Works great until 48-year old...
He's right. There is a limit to how close you can get metal to those loading coils before it disrupts the coil's tuning. That will drive up SWR. If you don't believe me, wrap your hand around one of those coils and see the SWR change from that alone.
73
Only effective way I know to tweak the VCO's tuning-voltage adjustment is with a 'scope.
The schemo is here: https://cbtricks.org/radios/cobra/132xlr/graphics/cobra_132xlr_sch.pdf
This radio has a somewhat-wacky PLL setup.
In most SSB CB radios you have a carrier crystal that's above the...
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