XTS5000 RX Failure - Bad Oscillator?

[Ken.Adams]

I've got an XTS5000 M3 UHF R1 that suddenly seems to have stopped receiving. I'm hoping to get some idea of what might be wrong and how to fix it.

When I open squelch with the monitor button I get static as you would normally hear on a clear channel, even if there is a signal on that channel. Occasionally I will switch to a channel and the radio will detect a constant carrier (red indicator light blinks) and if I hit the monitor button or disable PL, I'll hear a constant signal that sounds like a steady low pitched hum.

I'm not getting any error messages on power-up, and the radio seems to be transmitting fine. Channel Announce works fine, so I assume it's not an audio path problem. The radio has not been subject to any physical shock or exposed to water. I've broken it down and checked all the internal connections - everything seems normal. I removed the secure module temporarily to see if that made a difference - it did not. I've gone through the troubleshooting flow charts in the DSM and landed on "CHECK LO" - this is where I'm stuck.

First of all, does this sound like a local oscillator problem? If so, is there any way to verify this without removing the RF shield on the board to get to the oscillator? Is this even an issue I can fix, or do I need to replace the entire RF board? This is a personally owned radio used for Amateur service that I'd rather not send to the depot.