Thanks a lot, Mark.? After work I will scope Q6 and probably swap
for a 2N3904 running with 12V tops.? I will let you know results.
Bob
On 8/20/2016 2:15 PM,
mapn4dr@... [SoftwareControlledHamRadio] wrote:
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?
Bob:
?? I also had the same problem with both of my 49ers. The
first one was a blown driver transistor, Q6. It would work
for a few minutes and then..... no output. I placed my
finger on the transistor and it was too hot to touch!
I replaced it with a 2N3904 NPN (which was the original
driver for the 49er), and now it runs cool with the same
power output from the D882. The second one was a blown
D882. ?Several other possibilities are an open C15 or a
shorted D3. They would prevent drive from reaching the
D882. One quick way to tell if any drive is getting to the
D882 is to put a 'scope or simple RF probe on the
collector of D6. If there is no output there or very
little, then I would suspect a faulty Q6.? Unfortunately,
the design of this 49er is such that the D882 is driven to
close to the maximum limits on output. This stresses the
device, and makes it more likely to blow. As was noted on
an earlier post, reducing the DC voltage to the 49er to 12
VDC from 13.5 VDC reduces that stress, and allows it to
run cooler. A ?heat sink with an?appropriate amount of
heat sink grease is also important to keeping the D882
going.
??? Best of luck!
72,
Marc N4DR
