reforming electro's

[Jered]

Is it worth it and how long should it take for a 350 volt electro? Thanks all

[Phil_S]

IMO, no. It takes several hours.

[xtian]

And new ones are so much better.

[Phil_S]

...and relatively cheap.

[Leo_Gnardo]

What xtian and Phil_S said ^^^, and the old cap may still be unreliable after reforming. If it's your own gear and you feel you can take a chance on it, go ahead & give it a try. If it's a paid repair and must be made reliable for stage & studio use, don't muck around, swap in a fresh cap and be done with it.

If there's any goop leaking from the cap or it measures shorted with an ohm meter, have no second thought, heave it in the rubbish bin & replace.

[cbass]

It depends if you have some caps that you bought new that have been sitting for 5 or more years the yes its worth reforming

[Stevem]

It's project to do it right even if you have a good candidate to reform!

You need a way to start off at a low 40 to 60 volts and bring it up 20 volts or so every hour or two, and on top of that you need to have a small current / load on them, not just a voltage applyed to them to do the job right!
I have done this type of insanity for a few vintage nut cases and I get good money for it, but let me restate, they are nut cases!

The non metal cases Can types hold up far better over a 35 year span then the Axial types used in Fenders and what not .

If you have Cabin fever and its -20 out with 5 feet of Snow then reforming some Caps can give you something to pass the time, if not GET NEW ONEs!

[Jered]

I usually buy my electros from Mouser. I like new. But some one gave me some NOS Rifa cap cans 100/50/50uF 350V, Chemicon 50/40/40 350V, and Blue Seal 40/40/40/ 450V. I will just put them on the shelf for a later time. Thank you very much for your input

[Leo_Gnardo]

But some one gave me some NOS Rifa cap cans 100/50/50uF 350V, Chemicon 50/40/40 350V, and Blue Seal 40/40/40/ 450V. I will just put them on the shelf for a later time. Thank you very much for your input

The price was right so no harm in trying to re form them. If you have some spare time why not put 'em thru the process soon. That way if there's a dud you can dispose of it now, and once re formed they will be less deteriorated with time when you put them to work at some future date.

One careful method is to put a resistor between a variable hi voltage supply and the cap, say 100K 1 watt. Clip a voltmeter across that resistor, when the voltage falls to near zero, dial the hi voltage up a notch. The resistor will let the cap charge very slowly and hopefully rebuild its aluminum oxide dielectric. If you reach a threshold where it won't charge any more then you know you have a dud without having it go kaboom.

FWIW I have a box full of 400 uF 450V Mallory 'beer cans' dated 1966... maybe I'll try a re form on them for their 50th birthday.

[Phil_S]

An easy and low tech way to deal with reforming is to use the light bulb limiter. Start with a 5W and work up to 100W. Every hour or so change the bulb until you've got to full flow.