The original RCI 69FFB4 radio used four DEI copies of the 2SC2879 RF transistors for its built-in linear amplifier.
That part is a dog. The ones in this radio blew out fairly early. It sat a year or three before its new owner bought some legitimate HuaGao parts to get it back on the air. The black paint doesn't really obscure any part number. Rubbed it off and the surface under it appears blank.
But there's more to it than just four transistors. Never assume that transistors will be all that you need when they have failed.
It uses an oddball pc board to host the negative feedback (NFB) networks as well as one of the two output capacitors wired from one side of the output primary to the other. When I checked each one, they both flunked big time.
The surface-mount capacitors did not hold up well.
My solution is to use wire-lead parts large enough to handle the RF current without overheating.
Putting the NFB parts on a circuit board looks clever, but only if the parts chosen are up to the stresses of the job.
Showed nearly 500 Watt peaks AM, 350 PEP on sideband. Pretty mean.
73
That part is a dog. The ones in this radio blew out fairly early. It sat a year or three before its new owner bought some legitimate HuaGao parts to get it back on the air. The black paint doesn't really obscure any part number. Rubbed it off and the surface under it appears blank.
But there's more to it than just four transistors. Never assume that transistors will be all that you need when they have failed.
It uses an oddball pc board to host the negative feedback (NFB) networks as well as one of the two output capacitors wired from one side of the output primary to the other. When I checked each one, they both flunked big time.
The surface-mount capacitors did not hold up well.
My solution is to use wire-lead parts large enough to handle the RF current without overheating.
Putting the NFB parts on a circuit board looks clever, but only if the parts chosen are up to the stresses of the job.
Showed nearly 500 Watt peaks AM, 350 PEP on sideband. Pretty mean.
73
