Dear all,

I bought my breville 920 at 2019.

When I received a descale message from this machine. I had no idea but followed steps on the manual. In result, I've got '3-beep' error and dead steam boiler. I've been searching many articles from this forum and internet resources. And all of tips don't work for me.
I had diassembled the steamboiler from bottom to top many times. and cleaned the steam boiler seperately. and inspect inside of boiler -- no scale / no residue.

Here's my jobs on this machine.
1) I checked the steam boiler filling pump. When the steam boiler drained, it becomes filled out correctly and stopped. --> I think it has No problem with receiving low level / max level from water probe. and the pump works.
2) I totally disassemble the steamboiler --> I checked the steam boiler thermal fuse (167 C.Degrees, 10A) with tester. I found it blown-out and I changed it with one of my stock (210 C.degrees 10A).
3) And I checked the continuity between
A) TRI-AC output(brwon) - thermal fuse - heating coil one end : It gives abt 0 ohm. - Continuity is O.K.
B) heating coil both ends : it gives abt. 40 ohms - I think the heating coil is intact.
c) heating coil (2nd end) to rear fuse (round one at the opposite position of the thermal fuse) ends - abt. 0 ohm - continuity is O.K.
Therefore, I believed no problems at cabling and fuses.
I re-assembled coffee machine and try it.
4) But steamboiler still doesn't work but 3 beeps. (the steam boiler doesn't become heated.)
5) And I thought water pump filling has no problem, Cabling continuity, heating coil, fuses are intact. Then only one possible problem is the power source. Therefore, I changed the TRI-AC board.
6) But steam still doesn't work.
7) NTC - I tried to swap steam boiler NTC to coffee boiler NTC. And coffee boiler works. steam boiler doesn't work. --> So I think steam boiler NTC has no problem.

From 1) ~ 7), My diagnosis is that this BES 920 doesn't give signal to heat-up steam boiler.

And I checked the steam boiler NTC temp. reading / Coffe boiler NTC temp. reading as per Breville Dual Boiler Temperature Display

From this instruction, you could see the screen would show 'L LL' or "H HH'. But in my case, It shows 'H LH'.

I guess the first 'H' means the water level of coffee boiler. (because when I drained coffee boiler. it became 'L')
and the Last H means the water level of steam boiler (when I detached water probe line (red one), this letter became 'L')

But I can't figure-out the second letter, the 'L' in the middle of 'H LH'. --- Do you have any Idea?

And secondly, even I try to reset this machine as many instructions, I found 'clean me' message is always alive until I do 'cleaning' process actually. It means ---> this machine stores some logfiles inside of the control board and doesn't reset it. >> Do you have any Idea how to erase all, and get real factory re-set for this machine? Because there could be possibly some glitches on the logic of this machine , I want to reset all.

Your kind responses/advices would be highly appreciated.
Thanks in advance.