To Variac or not to Variac ....?

[steinjw]

Hello All - Pretty new member here, and could use some advice.
I am preparing to dig a set of monoblocs out of storage (B&K Sonata M-200s) where they have been for about ten years, in preparation for setting up a second system. At one point in the distant past I recall reading that one should not just plug into mains current in such a situation. However, some years ago when I considered doing this, I called a local shop, and as I recall they said "just plug 'em in".
Didn't have time to get to it then.
I'd rather go safe than sorry - can someone weigh in here and assist me in this?
And, if Variac start is the way to go, can you point me to someone in the area who could provide this service?
Many thanks - and - a pleasure to meet you all electronically!
Jim S.

[bmwr75]

Powering them up on a dim bulb tester first would tell you if anything is shorted in the amp.  It is pretty much a pass fail test.

No older than these amps are, I'd just plug them in an hope for the best if I didn't have access to a dim bulb tester.

[bmwr75]

You have read correctly that bringing up a vintage amp slowly on a variac helps reform the capacitors.  I have a variac and use it for this purpose.

[Mongojustpawn]

I would at least use a dim bulb tester, easy, cheap diy project, lots of info online.

[steinjw]

Thanks All - Ok - I have heard of dim bulb tester - I'll refresh by looking online - but I never thought that it could replace variac power-up. My lack of knowledge, sorry. Diggin' a little deeper on this end, then. Later ... JS

[Sir Thrift-a-Lot]

As I understand it, a dim bulb doesn't exactly replace a variac, but does add some insurance.   A dim bulb will let you know if there is an issue and buffer the potential damage, but it won't reform the caps like a variac would.   I've heard some people say that five minute power cycles once an hour or so, first on the variac for a few hours then without it for a few hours will help to reform the caps, but I don't know if that is actually true or just urban legend.   It seems reasonable to me, though.

[schwarcw]

You could buy a Variac online for $100 or less.  Might save you gas money and paying somebody to do it.

[bmwr75]

A dim bulb tester and a variac do not serve the same purpose. 

A DB tester is for determining if something is shorted in an amp.  It a short exists, the bulb will burn brightly continuously (no source or speakers connected).  If no short exists, the bulb will burn brightly while the power supply capacitors charge up (usually a few seconds) and then it will dim down to no visible light or a very dim light.  Of course the wattage bulb used in the DB tester makes a difference too.  I usually used one in the 75 watt range for most amps.

A variac is used to slowly bring the voltage up to an amp and allow the capacitors to reform slowly.  It will do nothing to prevent you from frying electronics if a short exists in the amp.

[steinjw]

bmwr: Yes, that is what I recalled regarding the dim bulb - serves more of a warning to "get out now" if things are not proceeding as they should, but doesn't serve the purpose for the variac power-up.

schwarcw: Oh great - now I must persuade "someone" that I need to purchase another $100 tool - got a tried and true script for that?

All comments are appreciated - thanks.

[MacGeek]

schwarcw: Oh great - now I must persuade "someone" that I need to purchase another $100 tool - got a tried and true script for that?

This is like Paul Simon's 50 Ways to Leave your Lover.

 You can sneak it in the house. I know I have enough tools no one will ever know if I add one more. If that won't work, hid it.  No one knows what is in the trunk of my car.

Lie about the price.  I have a friend who always told his wife the price for anything he bought was about 1/2 of what he actually paid.

Cut a deal.  Something for her and something for you (this generally works for me and while I might hide something, I don't like lying).

I don't know what the consequences might be, but you can always just do it and take the heat.