solution
hello mate,
i solve the problem by searching several forums like this one and i found wery similar walktroughs:
1: Load CZYŚCIK.bin BY COM(rs232 port)! use software HDUpgrader 2.25
2: Turn off receiver
3: IMPORTANT - Do not load new firmware!!!
4: load some file with settings/channels, no matter what it contains (for example s6f2a247_CH.bin) by software SetEditHomecast.exe
5: start uploading and loads LIST OF CHANNELS
6. on receiver screen appears S/W 00.00.00
7: don´t restart receiver
8: Loads factory firmware (for example HF8900HD_1.15.0A.sgn) BY USB
9: now U have original software loaded...
so, I did all steps till point 8 because I didnot found out, how to run upgrade by usb with almoust dead receiver. receiver did not respond to any usb stich a plugged feom front or back...
i just used HDUpgrader 2.25 once again and I load original firmware. to do so, upgrade procedure asked me to turn of and on receiver, so i did, and it worked. original firmware was loades succsesfully.
then U can load any other firmware by usb again...
good luck...