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

Dan,

Look for " Rough Service Bulbs ". They are still available and are incandescent. A plus is the filament is better supported for knocking around and are usually rated for a little higher voltage ~130. Farm supply stores should have them if the big box stores don't. 

73 Don ve3ids 

On Sun., Dec. 24, 2023, 11:23 a.m. Dan, <pitfit@comcast.net> wrote:

My startup rig is a 20A Powerstat variac, re-fused down to an appropriate level, a dim bulb tester, and a Kill-A-Watt meter, then the device under test. Works well. The Kill-A-Watt meter has to be slightly modified to display values at low AC input voltages.

Can you even buy incandescent A19/E26 base incandescent bulbs anymore? Maybe Amazon?

Dan
WB4GRA
> On Dec 24, 2023, at 10:43 AM, Jim Shorney <jimNU0C@gmail.com> wrote:
>
> 
> 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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