Cheap "variac". To good to be true?

[chocopower]

Hi there?
I found this in ebay. Is safe to use as variac for tube amp work?


https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.es%2Fulk%2Fitm%2F323583637603

[shooter]

probably, the specs and my Spanish are sketchy 
I'd make sure your "test" amp has a good fuse 

[kagliostro]

I think that isn't usable to feed amplifiers

seems to be a voltage regulator not a real Variac

Franco

[DummyLoad]

agree with franco: seems like a solid state phase control rather than a variable transformer.

i wouldn't use it.


--pete



BTW: the word "variac" started out as a general radio trademark for their line of autotransformers (variable transformer) first filed in 1933. general radio is defunct and a holding co., Instrument Service & Equipment, Inc. owns the trademark now. 

[chocopower]

Thanks.  Just what i thought.


I found this analysis (in English)
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.es%2Fulk%2Fitm%2F323583637603

[sluckey]

I found this analysis (in English)

Not my English. 

That is the same link as in your original post.

[vampwizzard]

Vary voltage up to 4000W. P = VI.. at 120V youre good up to 30watts of total current draw. (90% efficiency, 33.3 watts at 100% efficiency)

For small amplifiers this may be ok, but I would personally use a dedicated variac.

[DummyLoad]

Vary voltage up to 4000W. P = VI.. at 120V youre good up to 30watts of total current draw. (90% efficiency, 33.3 watts at 100% efficiency)

For small amplifiers this may be ok, but I would personally use a dedicated variac.

????

you do mean 30 AMPS, yes? 4KW at 120V would be 33.33A.


--pete

[PRR]

Just by the size, this can't be a 3000VA autotransformer.

The fit of screws/holes does not promise precision construction.

I think it is a lamp-dimmer. Incandescent lamps, simple heaters, etc. "Some" wall-power motors can be run on a dimmer. (Others burn-up and fill the attic with smoke....)

[chocopower]

I found this analysis (in English)

Not my English. 

That is the same link as in your original post.

Sorry....


https://owenduffy.net/blog/?p=11745

[PRR]

It is a triac lamp-dimmer. And not done well.

Aside from electrical shock, this will BURN a power transformer.