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Had to replace my K1, also. A couple observations.
Lead free solder SUCKS for desoldering. Pre-wetting it with a
little 60/40 makes it flow a bit easier onto solderwick.
If it happens once, it will probably happen again. The more you
work a board, the more likely a trace WILL lift, or a through-hole
will disappear. Instead of soldering in the replacement relay
(which may or may not fail again in the future), I used a dip
socket. Before the arguments against because of added lead
capacitance, etc., it works, the radio is happy with it, so I'm
happy with it.
On 8/22/2018 9:43 PM, Arvo W0VRA via
Good Evening, All.
My K1 relay was getting intermittently sticky on TX, so I decided
to replace it. I used an AXICOM with the same pinouts as the
stock Hongfa. I'm not very good at desoldering and tore up some
of the pads on the board. A little finagling and everything on the
DC side of the relay seems to be working. The connections labeled
TX on the schematic are getting 12V, and the connections labeled
RX are getting 12V when they're supposed to and 0V when they're
not supposed to.
But it's not transmitting. After studying the schematic for
what might be a problem with the new relay install, I'm
wondering what's the purpose of the RF side of K1? It appears
that when T/R is off, then the signal from the BNC connector
center goes through K3 and through K1 to the first set of
filters, and so on. When T/R is high (5V from the Raduino
signalling for transmitting), then K3 disconnects the received
signal trace from the BNC connector. K1 grounds the trace
coming from K3. Is this to prevent transmission RF energy from
bleeding into C80, causing some potentially nasty feedback?
And what would this have to do with the rig not transmitting?
The antenna signal is getting into the receive section, because
RX appears fine. If I'd done something wrong and K1 wasn't
interrupting the path from K3, then it should transmit anyway?
Am I missing something?
It's possible I damaged one of the delicate toroidal
transformers I suppose.
Any ideas will be appreciated!