I have a Royce i 620 that im scratching my head on. I have tried 3 or 4 different mics and I cannot turn the volume up hardly at all and it squeals. When I unkey the mic, I get a very loud BOOOOMP sound. Ive tried a turner jm plus 3, a plus 2, a unbranded power mic, 2 d 104s and a stock mic. I own another I 620 that doesn't have this issue, and I can run what I want on it..
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Royce i 620 mic issue.
- Thread starter rogodee
- Start date
Does that radio use a relay? It almost sounds like a "sticky" relay, where it hangs briefly, usually due to pitted contacts.
The squeal makes me wonder if someone's previously messed with the mic wiring in the radio. Squeal is almost always RF getting into the white audio wire, often due to issues with the mic cable ground..,...
The squeal makes me wonder if someone's previously messed with the mic wiring in the radio. Squeal is almost always RF getting into the white audio wire, often due to issues with the mic cable ground..,...
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Plug one of those mics in, take the back off, and use a multimeter to see if you have continuity between the mic cable ground braid and the chassis of the radio. If you have no continuity or any resistance above a couple ohms, then you have a mic ground issue.
Squeals on transmit are almost always due to poor ground and RF getting into the mic cable. In your case, you've tried several mics & all have the same symptom, so we can rule out the cable as a possibility. Could the mic plug on the radio be broken or missing pin(s)? Also, check the solder joints on the back of the mic plug inside the radio...... they often go bad after years of slight movement from mics being plugged and unplugged from the radio.
Squeals on transmit are almost always due to poor ground and RF getting into the mic cable. In your case, you've tried several mics & all have the same symptom, so we can rule out the cable as a possibility. Could the mic plug on the radio be broken or missing pin(s)? Also, check the solder joints on the back of the mic plug inside the radio...... they often go bad after years of slight movement from mics being plugged and unplugged from the radio.
Do the continuity test again but this time from the mic to the circuit board ground, instead of the chassis. Some older radios have a "floating ground" so they could be run on a 12 volt negative-hot system if needed. Let me know what result you get.
