Power transformer - good for anything?

[Ty_Bower]

I salvaged a small power transformer out of a dead 550VA UPS. It seems like it is a decent size - about 3" by 2.5", with a lamination stack 1 15/16" tall. The trouble is the secondary voltages. Since it came out of a UPS, everything seems geared for 12V lead batteries.

I put a test voltage on the primary. There are two center tapped secondaries. Based on what I measured, if I feed 120VAC into the primary I should be able to get 16.1VCT and a 31.4VCT. The 16.1VCT winding is really heavy gauge stuff, and I expect I should be able to get some decent current out of it. The 31.4VCT is significantly less substantial.

Is this guy useful for anything or is it just a waste of time? I'm wondering if it is safe to try something like wiring the 16.1V winding up to the wall, and taking 234V off the other secondary. I could put that through a full wave bridge for >300VDC. I recall warnings about sufficient insulation between windings, but I thought that was mostly aimed towards toroids.

[kuroguy]

put two of these back to back and you can get out what you put in with intermediate voltage suitable for 12.6 volt filaments. I've got two with plans to build a guitar amp. There's also a few mosfets that can be used for source followers.

[mcs]

Originally Posted by Ty_Bower

Is this guy useful for anything or is it just a waste of time? I'm wondering if it is safe to try something like wiring the 16.1V winding up to the wall, and taking 234V off the other secondary.

Don't do that! You'll just blow fuses (or melt wires). You need two transformers to get a high voltage output as suggested, or you could use it for powering heaters in an OTL amp

Best regards,

Mikkel C. Simonsen

[Tom Bavis]

You can't put much more than the rated voltage on a winding - core will saturate and there will be only winding resistance to limit current.

[bst]

I match up oddball transformers for use with oddball tubes. Your 16.1v winding would be good for powering pairs of 8v filaments. I've done this using a similar transformer (120v primary, 16.5v secondary / 2A) to light up pairs of 8SN7s in an aikido linestage.

The great thing about working with non-standard voltages is the components are dirt cheap. The previously-mentioned transformer was purchased for $4.00, and the 8SN7s were only 56 cents each in a carton of 36! Even better, these NOS 'chrome-dome' Rowland-branded 8SN7s had a RETMA code of 312, indicating that they were actually made by Sylvania. I've seen Sylvania 6SN7s go for over 25 bucks apiece; I like 56 cents better.

Skim through Frank Phillipse's excellent tube data site for tubes with heater voltages that match up with your (appropriately-loaded) transformer outputs. You'll discover a great number of very inexpensive and readily-available tubes that most people won't purchase due to the unpopular filament voltages.

[Tony]

I salvaged a small power transformer out of a dead 550VA UPS.

be carefull though that the 120 volt primary is not auto-transformer connected to the secondary....many UPS transformers i came accross are like that.

no problem if it is of the isolation types.....