Fix clogged prinhead, enter service mode HC5500

I have got a Riso HC 5500 with scanner and finisher. I bought it in UK, but the machine is located in Sweden, in a part which I probably not can get service assistance.

I have installed the machine, and the problem I have is the white lines all over the print. I tested the machine in UK and then it was hardly visible few lines, and as the equipment had been stored and not used for long, I thought it will be better after some use.

The printer arrived one week after my testing in UK, but show a very different print, with a lot of lines.

It is probably a lot of dry ink in the printhead. I have run cleaning a few times but it do not show result.

The ink in the machine was produced 2012, and it is not very much left on some colors, but not empty.

I have heard we can do a super cleaning from the service mode, and I have found some information, like to enter
the service mode, and the default password. Before I do it, pls help me how I find the super cleaning in the menu,
and how I exit service mode. Any other useful tips are welcomed gratefully.

The equipment I would use printing BW text and spot colors, the output should be OK for this when the printheads
works.