I have one of the earliest Flex-6600M radios released, as I was added to the Alpha Test Team.
As such my expectations have been from delivery that this particular radio would be likely to need some updating along the way.
I have been running the radio 24/7 since delivery, and though no performance problems came up the Heat sinks on the ADC boards fell off or slid down (one fell and one slid).
FlexRadio Systems had mailed a field repair kit and because I had no noticeable issues I put off installation until today.
Took me longer to gather my tools than do the job!
Basically you take the top of the radio off, remove a screw so you can pull each ADC board free, add the new heat sink while removing or securing the original heat sinks, reseat the ADC board, put the secure entry screws back, and put the top back on.
There are two heat sinks to deal with in the Flex-6600/6600M radios and just one heat sink in the Flex-6400/6400M models.
In my case I removed the original heat sinks completely, though some hams are securing them in place along with the new heat sink installation.
One wonders if there is a heat sink adhesive problem, as there are reports that some new Icom transceivers also have a heat sink problem. Not certain if those radios can be repaired in the field.
FlexRadio Systems released a PEN (Product Enhancement Notice) that covers the heat sinks and a preamp enhancement for 6m. I’m holding off sending the radio in for the rest of this PEN.
BTW FlexRadio Systems picks up the tab if you’d rather send your radio in for this PEN. My total time invested was circa ten minutes.