General purpose transformer?

[scatterandfocus]

I was going to add a 6.3V filament transformer to my components order list for use in an octopus component tester.  But maybe I should consider something with higher voltage and current handling for more general purpose use, such as making a first-time linear power supply circuit, and more safely scoping mains.  What other sorts of things could a general purpose transformer be useful for to a beginner?  What voltages, current handling, and other aspects might be good in a general purpose transformer?  Of course, a single transformer isn't going to be efficient for a range of uses, but it could be useful for exploring a range of beginner projects.

[Stray Electron]

  I would suggest looking for a variac so that you can set the voltage anywhere you want.  OTOH for any use that the operator might be exposed to the output then you'd need to use it with an isolation transformer. BUT both devices are very useful on their own. Both would be expensive to buy new but it's not difficult to find used ones on a site like E-greed or in surplus industrial equipment.

   I have several variacs including one permanently mounted in a chassis along with a voltmeter and an ampmeter and wired to a standard AC outlet. I use it anytime that I fire up an old piece of electronics gear in an effort to reform the capacitors in it and also to watch for possible shorts before I apply enough power (voltage) for a short to cause significant harm.

  IMO there's not really such thing as a general purpose transformer.  They're made for a WIDE range of output voltages and currents.

[ledtester]

Transformers tend to be heavy, so I would try to find them locally. A good place in the US are "thrift" stores like Goodwill, Salvation Army, etc. Also check if there are any "surplus" stores in your area.

An mains powered clock radio will contain a small low-voltage transformer like shown here:

https://youtu.be/M_FlSzwDKC4?t=1m20s

There are a lot of other older consumer goods that were powered by transformer wallwarts. They'll say they are DC power supplies, but if they are heavy for their size and look more like a cube rather than being rectangular it means there is a transformer inside. For instance, in this wallwart:



there is a transformer, rectifying diodes and capacitor.