With the help of George from GB Antennas (Dutch Acom dealer www.gbantennes.nl) I was able to figure out that my Acom 1011 does have the factory modification installed for improved tube life.
I emailed Acom and got a quick response from Val (LZ1VB). He confirmed the factory modification was in place so tubes should be safe. Even though the invoice is dated end of October 2012 (but also indicates amp was picked up by previous owner in december 2012), Val offered me to send a replacement set of power tubes under warranty. He also included detailed in structions how to install and bias the tubes. Not that’s what I call EXCELLENT SERVICE!! Acom really live up to the expection “for hams, by hams” and stand behind their products 100% Only for that reason, I would buy Acom amplifiers any time!
If you have an Acom A1011 amplifier and you want to find out if your amp has been (factory) modified to protect power tubes, read the article that I made (thanks again to George from GB Antennes): Checking your Acom A1011 amplifier for factory modification V1.0. You can also download it from www.mods.dk.