17% higher voltage to linear power supplies

[Potato Cakes]

Hello, everyone,

I recently acquired a balanced power transformer that is supposed to be 208/240V in and 120/60V out. However it is outputting 143/74V on a 240V connection (2x 120V) as though the transformer is 208 only. For gear with switch mode power supplies I'm not concerned, but with tube gear and amps that use linear PSUs, will the 17% additional line voltage be that big of a concern in a studio application? I have reached out to the manufacturer, but while I wait on an answer I thought I would ask here as well.

Thanks!

Paul

 

[Potato Cakes]

So, what I didn't know is that there is second red primary lead that is taped up and unused. I swapped it with the one being used and now the transformer is 240V in 120 out. In case anyone comes across an Equi=tech power supply that is 208/240, this is how you change it from one voltage to another.

For the purpose of science I am curious as to answer(s) regarding question asked above in this thread.

Thanks!

Paul

 

[cyrano]

You should measure output voltage with a load attached.

All transformers will have a higher voltage with no load...

 

[kooma]

If I would have to guess;
I would say that it could matter especially in some cheaper gear, where example capacitor voltage ratings may get bit too close to the limit..
and I would imagine that the extra heat is not good either, but on the other hand line voltages do vary a bit(or psu's should be designed so they could handle it)

 

[JohnRoberts]

Good engineering anticipates working under high line and low line conditions, but that does not mean it will be good for the gear.

As already shared weak link could be marginal voltage PS caps (typically in power amps). While back at Peavey we discovered one marginal (anti-sat clamp) diode inside a popular power amp module that would release its magic smoke, if customers set it for 220V and plugged into 240V for a little extra power.    After we upgraded to higher voltage diode the field failures went away. 8)

Also amplifiers with thermal shut down will shut down sooner.

Worst case for high voltage we encountered was Australian outback, where they jacked up the voltage before sending down miles of long power lines.

I personally encountered over voltage at my house here in the US, one night when my local sub station bump box (automatic stepping auto former) got stuck with too much boost and voltage kept climbing as load dropped off for the night. The utility didn't believe me when I called  and reported too much voltage but it was a slow night so the guy drove out and checked... My house power drop measured 275-280V... He drove over to the sub station and probably whacked it with a stick (carefully) to fix it.

JR

 

[totoxraymond]

280V in the US????

Aren't you supposed to get 110V/60Hz?

 

[JohnRoberts]

280V in the US????

Aren't you supposed to get 110V/60Hz?

Nominal us mains is 115-117VAC...  appliances run on 2x that so 230+. These are often rounded up to 120/240VAC for nice round numbers.

JR

 

[chops]

I wouldn’t want to plug a u47  with its unregulated PSU into a line voltage that was 17% over.  Unless I had lots of spare vf14 tubes  around...

 

[Potato Cakes]

He drove over to the sub station and probably whacked it with a stick (carefully) to fix it.

Reminds of a scene towards the end of Armageddon where the Russian cosmonaut is beating some computer box on the ship with a blunt object yelling "This is how we fix on Russian space station!" then the ship starts up.

I wouldn’t want to plug a u47  with its unregulated PSU into a line voltage that was 17% over.  Unless I had lots of spare vf14 tubes  around...

Fortunately, now I won't have to!

Thanks!

Paul