I have wanted to replace the transformer in my SX-43 for a while now.

The set requires: 117V primary, 530V/100mA, 5.2VAC/2A, 6.3VAC/4.0A

I can get a Hammond for this at a good price: http://www.hammondmfg.com/263.htm

I thought about a 270FX that is 550VCT and is a little better rated. The problem is the additional 20 volts: is it a problem and can the circuit eat it up and not worry?

I really want to avoid HV zener diode and/or resistor bleed-off solutions. I am not a fan of this.

The 550V rated transformer will be fine, as long as it physically fits the slight voltage difference won't have any impact.

Rodger WQ9E

The extra 20 volts is not an issue. High line voltage can supply an extra 20 volts with the stock transformer. If you want to lower the HV, use a bucking transformer.