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veriac/isolation transformer

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good evening too yous outthere.,,, I was woundering if anybody would have or know someone who might have simple plans for biulding an controlable 115/ac power/supply.,,, I've been reading on radio repair sites.,,, that an lower power/supply too bring the ac/line voltage up slowley too 115/ac is better then just plugging the radio into the wallplug.,,, and hopeing for the best.,,with the possibility of wrecking the radio toatly.,,, I have dabbled in limited electronics in the past?????.,,, it either worked or blew up in my face.,,, lmaorotf.,,, there are certian smells in life that are aggreable & some that are not.,,, like fresh/cut grass.,,, wienners & burgers.,,, not the accred smell of an bunch of expensive parts getting fried in front of you.,,, and oh! yeah.,,, that big puff of blue smoke luaghing in your face as the dollar sighns go billowing up towards the ceiling.,,, any-how.,,, if anybody has any suggestions.,,, I would be most greatful.

thankyou.

gbates6@cogeco.ca
 
Just be aware that a standard variac is not isolated from the AC line, thus there is a shock hazzard to ground. If you need isolation you can add a 115V isolation transformer either at the input or output of the variac.
 
A Variac with an ammeter is what you want for this. I've done this for years, and conserved a lot of smoke (improving my carbon footprint), and an uncountable number of sacrificial fuses. :) If you watch the ammeter as you very slowly increase the voltage, a fuse-blowing short will make the current climb very rapidly with a very small change in voltage. It's easy to back the voltage to zero at this point, unplug the device, make changes to isolate the short, and then try again.

As crutschow said, the Variac is not electrically isolated from the power line, so "always" unplug your device from the Variac while digging into it.

Ken
 
You may not want,,,,, to slowly,,,, power up devices,,,, that contain power MOSFETS. In some cases, the lo,,,,, wer voltage can cause ,,,,,the devices to dis,,,, sepate mo,,,, re po,,,,, wer than they do at full volt,,,,, age.,,,, lmaortongy!

Urp
 
So warned urp(?).

But, I only bother doing this on devices that have already blown a fuse. The idea is that you can start disabling parts of the circuit, from the blown fuse inward, until you stop getting the "shorted indication" on the Variac's current meter. Not the "be all to end all" solution...just another tool for some conditions.

Ken
 
re-isolation 115/a/c power transformer

goodevening gentlemen.,,, thankyous for your replies.,,, Mr. Bob Scott.,,, I understood the jest of your reply.,,, being.,,, you may not want to slowly power-up-devices, that contain mosfets, in some caes, the lower voltage can cause the devices to dissepate more power than they do at full voltage.,,,BUT YOU GOT ME ON THE.,,,lmaortongy! and the {Urp}.,,, be this as I only want to use the power supply on tube radios only.,,, as when I read about there repairs.,,, that it is advisible too increase the power very slowely too not distroye componetts in or on the chassis.,,,

I might hassered an guess,,,,,,,, laughing my ?ss off strongly!?:eek:

and the {urp} I don't have an clue.,,, lmorotf.;)


gbates6@cogeco.ca :confused:
 
I use a light bulb in series with the variac to limit the current. This has saved me a few times.
 
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