E29 code Error Toshiba KXO 80

The MAK card may fail due to the voltage drop on the lithium battery. In this case, the red LED on the MAK board blinks.
What happened? The initial data on the tube glow currents that were recorded in the SRAM U12 chip were erased, and when it is turned on, the checksum does not match. The MAK card is in a faulty state, as indicated by a red LED.
There is a main microprocessor on the SEQ1 board, which also manages the MAC card. To bring the board into working order, set the X-ray tube code on the SEQ1 card in accordance with documentation 2J314-012E (page 19). In this case, the initial data on the glow currents of the tube should be recorded in the SRAM U12 chip. But this does not happen, because the microprocessor on the SEQ1 board defines the MAK card as faulty.
What have we done? We had two faulty MAC cards. We counted the program codes recorded in the existing EPROM U11 chip (type 27256). We found in the program a place where there is a comparison with the checksum. Then they modified the checksum and recorded the corrected program into the new EPROM U11 chip.
What should I do to restore the MAC card?
Replace the lithium battery.
Remove the existing EPROM U11 chip from the MAK card.
Install the new EPROM U11 chip with the corrected program to the MAK card.
Switch on the X-ray machine and do nothing more! Now the red LED on the MAK card should not be constantly flashing.
Switch off the X-ray machine.
Replace the new EPROM U11 chip with the existing EPROM U11 chip.
Switch on the X-ray machine. And in this case the red LED on the MAK card should not be constantly flashing.
In accordance with documentation 2J314-012E (page 19) on the SEQ1 card, set the X-ray tube code.
The MAC board and the X-ray machine are working. If necessary, make the settings in accordance with the available technical service documentation.

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