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-   -   Best method of reducing line voltage into vintage transformers? (https://www.diyaudio.com/forums/tubes-valves/191621-method-reducing-line-voltage-vintage-transformers.html)

trobbins 28th June 2011 09:09 AM

Transformer insulation between primary and secondary, and secondary and secondary can be very different, and certainly requires different standards compliance. One meets basic/reinforced requirements, the other can be functional only.

The magnetising current increases with voltage. A normal transformer would have to cope with +10% rated mains voltage. If the original was rated 115, then you are asking it to nominally cope with 125+10%. If it was prone to getting hot at 115 (for example), then the balance may well be tipped at 138V.

costis_n 28th June 2011 10:42 AM

Quote:

Originally Posted by trobbins (https://www.diyaudio.com/forums/tubes-valves/191621-method-reducing-line-voltage-vintage-transformers-post2621855.html#post2621855)
Transformer insulation between primary and secondary, and secondary and secondary can be very different, and certainly requires different standards compliance. One meets basic/reinforced requirements, the other can be functional only.

The magnetising current increases with voltage. A normal transformer would have to cope with +10% rated mains voltage. If the original was rated 115, then you are asking it to nominally cope with 125+10%. If it was prone to getting hot at 115 (for example), then the balance may well be tipped at 138V.

Yes you should always observe the VA ratings of each winding and the total VA rating.


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