Vintage 70s gear rated 60hz on 50hz power supply? [Archive] - Audio & Video Forums


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04-15-2009, 12:39 AM
Hi there,
I'm hoping someone can help. I am interested in buying vintage Pioneer 70's reciever amps and there are plenty to choose from in the USA (E*ay) etc but they of course are all rated 120vAC 60hz.
I live in New Zealand where we are 230vAC 50Hz. Its easy to use an external step-down transformer but there will still be only 50hz. Does anyone know if this is a problem? is there enough iron in the main input transformers to run on 50Hz? Are the internal transformers simply a series/parallel primary winding arrangement where there are 2 say 110v windings in parallel for 110-120vAC supply and in series for 220-240vAC supplies? Would be good to know as there is heaps of this stuff in the USA and very little in NZ, could be worth all the shipping and additional effort.

04-15-2009, 05:57 AM
50 Hz does require more iron than 60 Hz. It is generally safe to run 50 Hz equipment at 60 Hz but not the reverse. The transformer may overheat. It may also produce excessive hum in the audio circuits and/or through direct vibrations.

Regardless of labeling, some designs do have enough margin to handle either frequency. I may be surprised but I doubt you'll be able to find a definitive answer for a given piece of vintage gear.

If the piece is not particularly precious, it's not particularly dangerous to try - if you smell or hear something funny, shut it down.

04-15-2009, 06:01 AM
The way a Pioneer engineer explained it to me when I worked for Pioneer as a technician in the late '70s, the power transformers inductive reactance would be designed around 55 Hz so the transformer would be fairly equally efficient and minimal losses at either 50 or 60 Hz.