I have checked all the components on the top of the RF board around
Q6. I have not removed the heatsink yet to check C122 and the other
components on the bottom of the board. Resistance checks show that R48
and R50 are correct. The DC voltages on Q6 should show some emitter
voltage when in TX, but the emitter is at 0VDC. The 1.8VDC on the base,
with 12VDC on the collector is trying to tell us something, maybe no
current flow in the transistor?
I have not seen or felt any evidence of overheating on any component
in the radio, at any time.
Gordon - N1MGO
On 3/4/2018 3:10 PM, Don Wilhelm wrote:
Gordon,
It is doubtful (but possible) that Q6 is bad. Did it overheat when
you powered up? - if it did, you would most likely have seen a wisp of
smoke.
How large is the signal at the base of Q6 when you have 800mV P-P on
the collector of Q5?
The base voltage on Q6 is higher than normal, it should be around 1.1
volts. I would suggest you check all components in the base circuit
of Q6 first.
73,
Don W3FPR
On 3/4/2018 2:26 PM, Gordon LaPoint wrote:
I'm building a K2 kit and I have a problem. I'm starting the
Alignment and Test, Part III on page 77-78. I have no rf out. I
have followed the rf through the tx chain and have a good signal at
(RF board) Q5 collector (800mv P-P) using a 400Mhz scope. I have a
signal on Q6 base, but nothing on the collector. The DC voltage (in
TX) at Q6 is 12.0 Collector, 1.8VDC base and 0 on emitter. I don't
see anything wrong DC wise, is it likley that Q6 is bad? What else
should I look for? With the radio off the R at Q6 emitter to ground
is 1.8ohms, that looks normal, so I don't have any current flow in
Q6, it looks like.
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