I had a similar situation several years back with an Icom 2720. I needed a temporary indoor setup, & used a mobile antenna near the radio. I didn't have the power cables coiled up, but because the antenna was within 10 feet of the radio, the transmit wouldn't let go. It happened with 2 radios. I moved the antenna a few more feet away, & the problem vanished. I am again using a similar temporary indoor setup, & the antenna is even closer to the radio, but this time it's a Kenwood TK840, & it's unaffected by the antenna. GARY N4KVEI think I've found the problem. I did SO MUCH reading on this everywhere I could find on the 'net and most of what I saw was concerning failure to xmit instead of sticking ON xmit. But the most helpful solution I found concerned the power cables and the antenna cable. My radio is set up as a base, sitting on top of a 25A power supply, and the stock power cables are still wrapped up in the original factory twisty with just a few inches of red and black wires routed to the power terminals on the supply. This bundle of wires is laying right next to the antenna cable. The article I found was about a mobile installation but it opened my eyes to the real issue-- When I pressed the PTT I think the antenna cable induced a voltage on the coiled-up power cables which affected the digital commands to the board to keep transmitting: in effect it never knew I had let off the PTT. I've moved the power cables/wrapping away from the antenna lead and the problem has disappeared.
Hope I'm right. And I hope this helps someone else.
I took my 133 apart to check and the only thing I found was that the rubber mat of keys was misaligned with the condenser mic and the hole. I just drilled through both (with the mic apart and the Circuit Board removed) So far everyone says my audio has improved on my 208'sSome years ago, when I picked up my 2nd or 3rd 208, I did a quick bench setup using a quarter wave antenna mounted on the radio with a right-angle PL259. I hit the PTT and all hell broke loose. The display went nuts, and the radio lost power, as nearly as I can recall. I immediately realized that 50 watts being radiated right next to the radio was not such a good idea.
And Rick, you might still wish to consider doing the microphone mods I suggested. The 133 is famous for producing thin-sounding audio due to the too-small mic hole and piece of black cloth that Icom puts over the mic element behind that hole.
Glad you found the problem.
Regards from DC.