Is converting a 220v PSU to 110v as simple as changing the transformer?

My naive thought is that the original power supply would have a transformer that accepts 220v and outputs X, which the rest of the PSU circuit can handle. So, it would seem that replacing the transformer with one that accepts 110v and outputs X would work, since the rest of the circuit would see the same voltage. Am I misunderstanding something?
 
Hmmm my copy and paste went a bit awry there. I had some more to add:

The rectification side of things has no care for where it's volts and current come from, so as long as it is supplied with a certain voltage X and the transformer VA rating is sufficient then all is good.

The need to update the primary side fuse is because for a given transformer rating the current draw at 110v mains will be greater than at 220v mains supply. Theoretically double.
 
Thank you everyone, you have been super helpful!

So, in order to identify an appropriate replacement transformer, I would need to know the output voltage of all windings (either from specs or from measurements).

The VA just has to be >= the requirement, right? So to be safe, I could always get a bigger transformer than needed.
 
  • Like
Reactions: 1 user
Moderator
Joined 2011
So, in order to identify an appropriate replacement transformer, I would need to know the output voltage of all windings (either from specs or from measurements).

The input is gonna be more like 120VAC in the USA these days, not 110V.
Check whether the original has dual primary windings that can be configured for your AC line.

And each secondary winding has to be adequately rated for current, as well as the right voltage.
 
Use a properly rated step down transformer, a custom transformer will be expensive to specify and procure.
More flexible, can be used for other equipment also.

Just make sure the 220 V unit cannot be plugged into a 110 V line.
Provided of course the unit is working.
Also, it may have the 120 V winding tap in the original transformer, just check that first.
 
I thought that they snuck it up again in the US to 125/250.
Just measured mine in Fl. USA , 125.75V
I'm old, I remember 110, 115, 117, 120 and now 125
being what they provide given their tolerances.
Oh, that was measured with the AC running.
 
Last edited: