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Bearcat 880 no transmit

Patriot2Alpha

New Member
Apr 15, 2023
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Hey yall! Green mountains here waving! I have a bearcat 880 for a buddy, I can't get any transmit out of it but I do get sound through the PA great recieve audio just no transmit. I changed the finals still no luck. I have genuine Mitsubishi ones on the way. Any where else to look for the issue?? Thanks in advanced!
 

I would start with a radio on the same channel, and see if you hear anything at all from this radio when it transmits. A coax jumper on the monitor radio with the shell backed off the connector at the far end gets you a half-inch long "sniffing" antenna you can poke around the transmit mixer chip in the 880.

If you can hear a weak signal, the problem is downstream from the mixer circuit.

If you hear nothing, there's no point to molesting the driver or final just yet.

A DC voltmeter on the metal tab surface of the final transistor should show around 6 to 7 Volts DC in AM transmit, and around 13 Volts sideband. If not, the modulator transistor may have failed.

Test the old final for a short between collector and emitter. If it's shorted, this would suggest possible damage to the modulator transistor.

73
 

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