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 What the heck is a "Dim Bulb Tester?"

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FrankB
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Join date : 2010-11-22

PostSubject: What the heck is a "Dim Bulb Tester?"    2017-08-26, 6:11 pm

I was recently asked this question, so here is the answer:

The Dim Bulb tester is simply a light bulb (NOT AN LED or flourescent bulb!) that is placed in series with the hot side of the power cord feeding your radio, amp, etc.

I used a couple of old outlet boxes and was lucky to find a screw in fuse holder, with switch on the same face plate, and the fuse holder has just the same basing as a light bulb has. (Habitat for Humanity here has some nifty things at times.)

I placed the single outlet/ SPST switch in one duplex box, and the fuse holder/bulb socket in the other duplex box. I added a bit of leftover spray paint and VIOLA! it was done. 

It's not fancy. I do plug it into my PR57 or a Variac (r) (with an isolation transformer. ALWAYS use an isolation transformer, especially on "hot Chassis AC/DC sets.

 Screw in a bulb that is of higher wattage than I expect the radio, amp, etc. to draw.

  Embarassed  (Don't ask! "What do you mean, the main breakers for the building tripped again?" "All I did was to hook up the ground lead from the Telequipment scope to the chassis......")   (Gotta love tech school teachers that know theory, but nothing practical. Twisted Evil)

If the bulb lights up really bright, likely you have a short (Mainly filter caps') in the radio.
 If it stays dim, the radio will likely have no major fault.
 Basically, it's a current limiter. I keep several different wattage bulbs around to screw in as needed.

One day, I will build another "Test Panel" version, in which I can select the bulb wattage with a turn of a selector switch.

With experience, and a bit of plugging in good sets, you can make a good guess as to just how bright the bulb should be, and what wattage you should use.
 (And yes, the brightness can vary, depending on how loud you have the radio also. The louder it is, the more current that is drawn.)

 Note: This tester will NOT work on many of the more modern TV sets, as the SMPS are fussy, and some need that initial current surge to "Get up and going" . But on any of the old transformer operated sets, I never had any problems with it, excepting some TV's that did need a faster current draw than the bulb would let through. Mainly a few models of RCA color sets.
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