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Running Power Transformer 'unloaded'

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Posted on August 24, 2015 at 16:58:13
rogerh113
Audiophile

Posts: 507
Location: San Francisco South Bay
Joined: October 20, 2014
 Hello,

Just starting to FINALLY build up my project. My plan was to build up the power components and test them prior to doing the signal wiring. Is is a problem to run a power transformer without load for an extended period of time? I am planning to bring it up slowly with a variac and check voltages and current on the way up. I generally like to take my time and be thorough, so I could well be a half hour or hour at it. Is this likely to be a problem with a decent power transformer?

Regards -- Roger

 

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RE: Running Power Transformer 'unloaded', posted on August 24, 2015 at 17:17:02
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 Generally speaking you should be OK to run a power supply unloaded for measuring etc. for a little while.

Try to minimize breadboard operation for safeties sake. 1 1/2 our seems excessive.
Is this a vintage/antique transformer?

If the transformer is new, it should measure fairly predictable, albeit a little high when unloaded with the intended voltage on the primary.

If you want to test different power supply configurations, you might try a power resistor as a pseudo amplifier stage load.

PSUDII is also an invaluable tool for basic power supply rendering if you aren't already using it.
Quick simulations can save days of bench experimenting, which also minimizes exposure to high voltage testing situations.

Have fun

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RE: Running Power Transformer 'unloaded', posted on August 24, 2015 at 17:40:48
Paul Joppa
Industry Professional

Posts: 7295
Location: Seattle, WA
Joined: April 23, 2001
 I agree with Garg0yle.

While you are at it, measure the AC voltage on each winding at your normal power line voltage. These voltages, and the DC resistances of the windings, are needed for PSUD.

 

RE: Running Power Transformer 'unloaded', posted on August 24, 2015 at 18:47:44
rogerh113
Audiophile

Posts: 507
Location: San Francisco South Bay
Joined: October 20, 2014
 Thanks for the input. It sounds like I should build up the entire amp and then bring it up slowly with the Variac and do the checking I want to do. I will have some NOS caps in the amp, and wanted to bring them up slowly so that if any reforming is necessary it will happen. Just thought I might be able to split the workload and get the power side of things shaken out first.

Regards -- Roger

 

RE: Running Power Transformer 'unloaded', posted on August 24, 2015 at 19:28:57
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 By all means carry on as you were.

Bringing up old caps slowly might not be a bad idea.
I would bother with any older electrolytic capacitors though.


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RE: Running Power Transformer 'unloaded', posted on August 25, 2015 at 03:48:30
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 I think what gargoyle meant is that with all the great caps avaialble these days there really is no need to take a chance on old caps. Use high quality new ones and get years of trouble free enjoyment. Lots of info on cap types and their sounds on the web.

 

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