Andrew VK3BFA wrote:
mike wrote:
John, N9JG wrote:
Your advice is elegant in its simplicity.

And OPTIMISTIC in it's generality.
While one might imagine situations where this technique is
useful, it would be better to define a strategy that takes
into consideration the exact configuration of the PS in
your unspecified amplifier.

Gee, that sounds like the opening page of a PowerPoint presentation -
your not a manager by proffession, are you?

And if you have an engineering degree, and want to engage in endless
metaphysical speculation, thats a very good idea.....whatever it
was.....amongst the verbiage....

If your caps don't need reforming, any technique will work.
If they do, you're gonna have some current flow. It's not
hard to imagine a scenario whereby you have 25W or more
dissipated in your caps. I don't call this safe. A 100W
light bulb will keep you from blowing up the rectifiers while
you're blowing up the caps.

Rubbish. Where do you get this 25w figure from, and across how many
capacitors in a (typical) series string - oh, and lets ignore idling
current through transformer and bleeeder resistors, and filamnet
current drain, and blowers, and dial lamps, and.....which would further
reduce available volts across the caps.... And whats this "imagine a
scenario" stuff - I thought you were trying to be precise and were
chiding me for my lack of hard data....

Assuming you have solid-state rectifiers, go back to the
variac and transformer. Depending on the value of the high voltage,
There may be issues if you just turn off the tube filaments.
The series lamp can still be helpful, but isn't the whole story.

So, what voltage do you set the variac too? - how do you work it out?

It's always helpful to disclose the parameters of the situation
when asking for advice. Otherwise, you'll get 10 different
solutions based on 10 different assumptions, none of which will be
correct.
mike

True. There are probably 10 different ways of puting out a fire, but
the easiest is dumping a bucket of water on it.

Honestly, this is ridiculous - most modern (ie, last 40 years) caps are
fine, will survive horrendous abuse, and unless you have the
manufacturers data sheets for these capacitors, (and the power
transformer, and the rectifiers) how are you going to set these
parameters anyway? - this is a linear amplifier, not the space shuttle.

Why do people insist on making things sooooo complicated, almost
theoretical physics level - it isnt. Dont let irelevant theory get in
the way of practical electronics.

The intial switch on of ANYTHING that hasnt been powered up for years
is going to be the time it dies - at least the bulb will stop it
bursting into flames, the variac method will jsut slowly ramp up volts
until something blows catasphropically (I know, used to do this, got
sick of replacing fuses in the variac.)

As well, you have the added complication of multiple, lashed together
transformers which MUST all be correctly phased and able to take the
load current . a recipe for confusion at least.

And no, I cant spell. Spend too much time with soldering irons rather
than physics journals.

Andrew VK3BFA.

All he was asking was how to hook up a variac. Seemed simple enough.

Gary N4AST

j

All he was asking was how to hook up a variac. Seemed simple enough.

Gary N4AST

True. But why lose the chance for an argument? - my issue was with the
over complication of a simple task....and if someone needs to ask
questions on how to set up a variac and a transformer, then the keep it
simple approach (ie, the light bulb) has much to recomend it.

Andrew VK3BFA.