Quote:
Originally Posted by ALTEC9846-8A
My set has a separate power supply with 2 5u4 tubes. I just got it and haven't got it out of the cabinet yet. Does your schematic show a separate power supply with 2 5u4 tubes?
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To be compatible with 25Hz you have to prevent the power transformer cores from saturating by more than doubling the size of the transformer relative to the 60Hz American design. The American RCA 721 this is based on has 2 5U4s and a smaller power transformer. Your set is probably a direct copy of the 721 with the power transformer, choke and the first 2 lytics doubled in size and the ones too big to fit the chassis moved to the subchassis. That was basically SOP for Canadian RCAs and clones from 1946 to the CTC5 color sets of 1956. If you have TV experience you could probably service it off the RCA 721 schematic noting that the installed pi filter lytics would be bigger in your set.
25Hz sets will work fine on 60Hz... however 60Hz sets will have nasty hum and the power transformers will rapidly burn out if powered by 25Hz.