Trying to decide which amp to buy, not too much difference between ACOM's 1500 and 2100 models. Anyone know if they are using SVETLANA or chinese tubes in current production ? The only difference I can figure by spec sheet is the transformer is heavier on the 2100, runs more plate voltage. Both have 3 antenna ports, both capable of 120 volt operation, ( at kilowatt level ) for emergency field use on generator power. One more consideration, regards repairs: Is service literature available for the modern ACOMs ?