Re: [Amateur-repairs] SETTING UP A TEST BENCH

Another thing worth noting is that makers of variacs often skip putting a fuse on the output side. Think about transformer theory and you will see why this is important.

73

-Jim
NU0C

On Sun, 24 Dec 2023 09:03:18 -0500
"Tim Reimers KA4LFP" <treimers95@gmail.com> wrote:

> "A good rheostat for slowly powering up something that make have been turn
> off for the last 20, 30, 40 years."
>
>
> Couple of points here
> A Variac (what you're talking about when you say rheostat)
> Does NOT LIMIT CURRENT.
> A dead short in a DUT will still destroy components like the DUTs power
> transformer, even sometimes at the low voltage a variac provides.
>
> Also, a Variac does not protect you from the AC line. A large (massive)
> number of old shortwave radios and other audio gear had "hot chassis"
> designs, with no power transformer, and the chassis was physically isolated
> from the case.
> A so-called AC-AC design.
>
>
>
> Best design for a power system for your bench:
>
> Separate GFCI circuit feeding a large isolation transformer, in series with
> a Dim Bulb Tester in series with the Variac.
>
> The Dim Bulb Tester does limit current to protect you from those dead
> shorted dried out capacitors that will let all the unobtanium smoke out of
> your power transformer.
>
> 73, Tim KA4LFP
>
>
>
>
>
> Morse Code: The original digital mode.
>
>
>
>
>



--

73

-Jim
NU0C


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