Before the keygens or the ATtiny85 hack, the way that many of us owners were getting around the problem of expired options was by using a clock reset/self-cal exploit to restart the trial minutes.
If A-model owners are still unable to use existing keygens after downgrading, this might help them, at least until a permanent solution is found, to continue to have access to the various options. The technique is known to work for sure on FW versions <= v.01.00.00.03, but since the other hacks first started coming out around the time of the release of v.01.01.00.02, I'm not sure if it has ever been tested on that (or any later) version.
If this doesn't work on current versions (>= v.02), an A-model owner could then downgrade and run the technique again, but the question then arises as to whether the change to the structure of unit settings stored in FRAM would allow the trial minutes to be maintained when upgrading back to v.02.01.00.03. Certainly there is no harm in trying - worst case scenario is that trial minutes are lost when upgrading from a v.01 to a v.02 firmware.
Since I got an official key some time ago, it's been quite awhile since I used this technique myself. The latest versions of the technique that I post here are courtesy of forum member Wim13, who did many hours of testing on it. He may have a more updated version which he could post - I'll leave that to him.
The techniques (known to work in versions 00.01.00.02 -> 01.00.00.03 at a minimum) are as follows:
Manual:
Make sure System -> Startup is Default.
Set the clock to 2099, 31 Dec, and 23:58 hour.
Wait a few minutes for the clock to rollover past 00:00 (you can see it in the normal screen at the bottom right),
Put the clock back to the correct date and time.
Reboot
Wait at least 30 minutes for warm-up, then do a self-calibration.
After the scope is finished, it will reboot once.
Make sure System -> Startup is Default.
Then you just have to wait for awhile. The options will come back sometime when you boot up between ~3 to 60 hours later. You don't have to leave the DSO turned on (you can just use it normally and turn if off when finished), but the best success for getting them back on the next boot-up seems to be if you leave the DSO turned on for another 3-4 hours after the self-cal.
By SCPI via LAN or USB:
:system:pon def
:system:date 2099,12,31
:system:time 23,58,30
Wait 10 minutes
:system:date?
[if date is 2011, then:]
:system:date [whatever the current date is]
:system:time [whatever the current time is]
:system:reset
Reconnect LAN/USB
Wait 30 minutes to warm-up
:calibrate:start
Reconnect LAN/USB (lost connection after reboot)
:system:pon def
Then loop for every hour or so,
:system:reset
Reconnect LAN/USB
According to Wim13, using this technique restarted his options on the 4th reset with 2158 minutes.
Total time from first reset to recovery of options: 270 minutes.