Sorry Hipogrito,
Sorry Fran,
The service bulletin you have sent to the service centers has it as an attachment http://jirin.web.althan.cz/201705-kurzw ... -solution/, if you want to download and view. 
This was done on my synthesizer, installing the latest version of OS V2.26, but the "Blinking problem" was not finally resolved, the PC3LE was working normally for about a month, and then another problem occurred - there was no sound at the three outputs. This unfortunately happened to other unfortunate owners of Kurzweil PC3LE. 
I listened to your advice and contacted via http://kurzweil.com/support/repair/ with the Kurzweil Authorized Service Center in my country, describing my problem and being the second owner and the warranty is over. They did not ask me to send the board but I received an email that Kurzweil had given instructions to replace MAIN BOARD. Service asks me to pay about 450-500 euros - OK, but they do not give me any guarantee that PC3LE will work and will not repeat my problems.
Do you think this is some joke ??? I have emails my correspondence with the so-called "Authorized Service Center of Kurzweil" and I do not know what decision to take .......... 
Hi,
Sorry about your problems.
So, are you saying that Blinking problem was actually fixed and now you have a different problem: "there was no sound at the three outputs"?
Regards,
Fran
Hi,
Sorry about your problems.
So, are you saying that Blinking problem was actually fixed and now you have a different problem: "there was no sound at the three outputs"?
No Fran, obviously no different problem , see this comment:
"UPDATE: I talked to Jean at Kurzweil Tech Support for 37 minutes and he was also talking to the guy in the parts department at the same time. The keyboards have been updated at the factory with the updated cables, and the keyboard will have the updated cables.
When I sent my keyboard to Sweetwater Music for repair under their two year warranty they replaced the two power supply cables with the updated ones. The keyboard still had problems, so they replaced the power supply, the LCD readout screen, and the main sound engine board. They sent the keyboard back and it worked great for about a month then it had problems again.
After a month, my keyboard had another problem. The audio output would turn off sometimes. No sound through the L / R output jacks or the headphone jacks either. This would happen once in a while and the sound would come back on. I worked out a deal with Sweetwater Music where I bought the keyboard from and got a store credit which was prorated due to I had the keyboard for 2.8 years. I used the store credit and a lot of extra money and bought a new Kurzweil PC3K7. "
The comment is taken here - https://www.youtube.com/watch?v=e6fWdv1_TSM
And when you read the other comments, you understand that the problem is factory !!!
I think it's time for a new topic ! 
