filter cap replacement -'forming' the caps?

[guitarpsych]

I have never done this but I have heard people talk about a need for 'forming' the caps when replacing the filter caps... Can someone please describe this procedure and how necessary it is?

I just replaced the filter caps on my ST-70 without doing anything special regarding a procedure of running current through it... Just wondering if I should be doing something special with this.

[kheper]

I have heard people talk about a need for 'forming' the caps when replacing the filter
caps.

Do you mean to say that you've replaced
the multi-cap for the power supply, the
cap which filters the high voltages off
the rectifier tube?

The procedure is used to re-form caps
which have sat idle for many years. It
involves hitting the caps (and the rest
of the amp) with small, incremental
amounts of voltage with a variac, to
slowly re-form the caps and to
diagnose any problems with the
amp which might become evident.

The procedure is documented here:

http://www.hhscott.com/cc/1st_soft_start.htm

However, you do not need to form or
re-form a new cap.

Had you been using the st70, in the
recent past, before replacing the cap?

[guitarpsych]

Thanks for the link and info.
Yes, I'm talking about replacing that big metal cylinder capacitor that is shaped sort of like a tube. I have been using this amp for a while and have been replacing a bunch of parts.

I was also asking in general, because I have replaced filter capacitors in guitar tube amps and also made a few guitar tube amps and I have never done a special powering procedure related to the filter capacitors... and the tone sounds great. So I was just checking the knowledge base here to make sure I was not missing an important procedure. It looks like I am ok. Thanks.