?Hello,
I will not write too much more than previous colleagues - I also would start checking relays. Yes, relays. RX path goes through TWO relays K3 and K1 (type HFD27/012-S relay).?
By default RX path is shorted with pins 11-13 of K3, but also M1-M2 points just before audio amplifier are shorted during RX with K3 4-6 pins.
K1 relay shorts RX path through pins 4 and 6, but also powers RX or TX sections through second pair of contacts. So there are a lot of relay contacts which are influencing correct TRX operation. Not only passing radio signal through, but also powering of RX/TX sections. So in first place correct relays operation must be confirmed before we will go further. Contacts view from the bottom:
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I would start from bypassing (shortening) of pins 13-11 and 4-6 of both relays (K3 and K1) and would check for correct RX operation - all middle pins of K3 and K1.
!!!BUT be aware not to perform transmit during bypass because You will BRICK the radio! Replacing relay is difficult and needs good preparation/strategy.
It is large component with 8 legs - it is difficult to heat all them together and not break the PCB traces - via holes. Someone will use hot air, someone two irons and big drop of tin to heat up all legs simultaneously and carefully lift relay. Second person help may be also useful. Do no hurry. Another way is to carefully destroy/break the relay and try remove carefully leg one by one. Most important not to destroy the PCB/delicate via holes. So as You see replacing relay might be a challenge - so first make sure one of them is a root cause. If You will decide to swap - You can watch for better quality ones. I think OMRON G5V-2 12VDC is also a replacement. They are widely available. Or am I wrong? Good luck. Give us feedback. Regards. Tomasz
tomekdm sp7etd