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?
You also need to increase the primary fuse rating, if present.
As long as the new transformer has the same secondary voltage, the VA rating is correct and you increase the primary side fuse rating, you are good to go.
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.
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.
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.
Yeah you need to make sure the secondary winding voltage is the same. Having a bigger VA rated transformer won't harm anything. It might be phsically larger so just check the size to ensure it fits where you need it.
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.
I never know what values to pick when I'm specifying voltage... 110/220, 115/230, 120/240. They all mean the same thing, it's not like products are made differently for homes with 110 vs 115 vs 120.
Did it used to be standardized at a different voltage and is now standardized at 120? Or has it gradually increased over time?
I think the 'standard' has increased over time. I recall (seeing old things in the 1970s) namepaltes saying for line voltages of 105, 107, 110, 115, 117, and now 120 since probably the 1950s. This starts at an earlier time period:
https://en.wikipedia.org/wiki/Mains_electricity#Standardization
https://en.wikipedia.org/wiki/Mains_electricity#Standardization
Was originally 110, then 115, then 120 by the 80s. Not likely to go down at this point.
Higher voltage on the same size wire means higher power. Copper is expensive.
Higher voltage on the same size wire means higher power. Copper is expensive.
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.
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.
Since 120V at 60Hz has the same flux in the core as 100V at 50Hz, only a 100V stepdown should be used.
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.
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.
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