Then you have to open it up and by voltage checks, find out what is
causing it to transmit. It could be many things: It could be that the
transistor that supplies +TX has shorted. I could be that the microphone
cable ground has broken and the resulting hum pickup is triggering the
VOX. It could be that a stray strand of wire has fallen across the ptt
line. Or key line. Or that its ROHS and the tin of the lead free solder
has grown a whisker causing a short. You have to trace from the TX+
switch through all the control circuits because any one of them can
cause the problem, there is no place likely to be more suspect unless we
get to troubleshoot many of the same radios with the same fault. Likely
there are cables between boards that you can disconnect to isolate some
of the potential transmit triggers to isolate them. Others you may have
to isolate by cutting traces on boards. Or use a millivoltmeter to find
the lowest DC voltage on the accidentally grounded trace, but with only
milliamps of current you might need a DC microvoltmeter to find
differences along a trace. The DC millivoltmeter works good for finding
grounded power traces when you can limit the DC current at the power
supply to an amp or two. The closer to the short you measure, the lower
the voltage you find.
73, Jerry, K0CQ
On 8/8/2010 3:26 PM, F8EHJ wrote:
Thanks Erik,
I am happy to see that you solved the problem but I don't have any
acc cord plugged on transceiver.
I unplugged all cable and antenna. After performing a master reset, I
have always the same fault.
When I change the frequency to a non amateur band, the jupiter switch
to rx mode, it is in tx mode else.
73's
Hervé F8EHJ
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