[volt-nuts] Safe power-up. was (Solartron 7075 ...)

WarrenS warrensjmail-one at yahoo.com
Mon Oct 10 20:01:12 UTC 2011

I don't plug ANYTHING new to me, directly into the line the first time I try 
(especially if it had a blown fuse)

Here is the solution that I use for a universal, general purpose, tester for 
Old (and new) equipment.
This is a great tool that can be used for trouble things that draw too much 
current, has shorts, for reforming caps, Testing line voltage sensitivity 
etc, etc.

First time powered up test equipment is powered from:

1) A line voltage rate light bulb in series, starting with a low wattage and 
working  your way up.
The light bulb acts Nonlinear variable dropping resistor, which act like a 
current limit and will limit the max current to a safe value but still have 
minimum effect at lower currents due to it's Hi TC.

2) The voltage to the Light bulb comes which from adjustable variact.
The voltage rise and the Time at each voltage setting is a learned function 
and depends on what is being tested.
If you're in a hurry, set it to the nominal line output and flip the switch. 
The rest of the stuff will still provide protection.

3) The Variact is plugged into a KillAwatt meter
Used to constantly monitor the power, If it shows too much power is being 
used, ... Well don't let it do that..

4) The Kill-a-W is plugged into a solatron 1 to 1 line regulating 
My Line regulating Solitron has the very desirable built in characteristic 
that it goes into a saturation mode that limits the max output power if 
If not overloaded, it outputs a constant voltage.

5) Have a few resetable and/or  standard  fuses in there to be over safe.

The proper use of the variact's output voltage has a learning curve, because 
equipment with switchers behave differently than things with linearly 




I picked up a dead 7075 recently, I found that the fuseholder was not making 
contact with the fuse, fixed that fault and now the PSU area was making a 
fizzing noise. I disconnected the mains straight away. I presume I need to 
reform the main capacitor with a dropper resistor. Is 33k a suitable value, 
or should it be done at a lower current than that?



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