Receiver Won't Receive
Problem: My MarkV
would not receive. I got back into town last night after a week
away from home on business and continued digging into my MkV to
troubleshoot the lack of RX.
Solution: As
said last week, there is a T/R circuit at the antenna input to
the rig that employs three transistors, a pin diode switch, and
a relay. The relay wasn't being activated. I was able to make
the relay work by supplying 12V to it and the rig received fine.
Today I did some troubleshooting and found that Q6451 was bad. I
replaced it, and while I was at it, I also replaced Q6450. I
verified correct operation of the circuit and the rig works FB
now.
Troubleshooting the problem and replacing the transistors was
relatively straight forward. Digging into the rig and getting
the main antenna tuner board out was pretty tricky. If you have
any questions, don't hesitate to ask.
Lou
W7HV
Deaf Receiver (Mark V)
Problem: "During
contests, anything can happen. For me it happened.
Two radios + amp end up to same freq,
and just few VOX TX clicks made
the receiving radio deaf. by
Jussi-Pekka, OH6RX
Solution:
I assumed (from block diagram) that the
tuner main unit didn't fail and that it has be to related to
RF-unit. I followed schematic from input (from tuner main unit)
until to BPF section and measured all semiconductors
which were connected to input signal
path. I found only one PIN diode
had failed (disconnect), D1056, 1SV271 Toshiba pin diode.
IRmax (reverse) with VR 50V only
0,1uA. VF 50V and IF
50mA. Just in case I measured
the whole BPF section PIN diodes, to be sure that it was
working. Opening/closing the radio takes quite a lot of time. No
other failed components.
For checks, you don't have to close all
screws and blocks, just make sure that
loosen parts wont make any more damage."
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