Electrolytic capacitor re-forming

[kriegsfunker]

WARNING!  This topic relates to voodoo, black magic, and horrible superstition.

 

Anyone have luck with capacitor re-forming?  If yes, what is your magic formula?

[val]

You could try this, but i have never tried it by myself, so...use it at your own risk

https://www.qsl.net/g3oou/reform.html

[Funksammler]

If the leakage is not too bad, I leave them in place, otherwise I replace them. I don't have a hard and fast rule for "too bad", I guess it depends on the effect on functionality. If the leakage is blowing your fuse or threatening your rectifier, I would definitely replace straight away...

Regards,

Funksammler

[tornfuté]

FS did you find easy capacitors of 10 UF 1.5 kv till 3 KV? I have oil capacitors 

of 1 or 2 Uf 1000v but  it’s difficult to  find higher

regards

 

[tornfuté]

Some capacitors  of 1UF 2UF and 4.7UF it’s oil capacitor as when i sake 

i heard oil moving  difficult to insert such  items  in original ones

[Funksammler]

I have some limited old stock of HV capacitors, otherwise it is possible to build using modern Elco's. Elco's up to 500V are easily obtainable, you can put them in series for higher voltages. Because modern Elco's are so much smaller, they should easily fit in the original housing.

regards,

Funksammler

[tornfuté]

Of course but it divides the value  , you need more to reach the right voltage

and  replacement value , hence less place inside container

Regards

[kriegsfunker]

My NA8 has electrolytics in bakelite boxes.  First time I have seen capacitors in bakelite.

 

 

[val]

SAF is Süddeutsche Apparate Fabrik GmbH

[kriegsfunker]

That's the manufacturer of both NA8 power supplies that I have seen.

Edited January 15, 2019 by kriegsfunker

[tornfuté]

It will be usefull for restoring  psu that are over the usual 350 -400v 

 to describe how to fill new elcos.

i guess the german proof their elcos to high value , if we consider  a 

working voltage of max 1000 v , i believe a final  isolation  value of 2.000V will  be enough for such output voltage .If we put 5  elcos 120 UF  500V in serie 

it makes 24 uf  2500v. But i remember from school time there is neccessary

to put  on capacitor a resistor  to avoid damages.What will be the value,?

120 UF size is 20 x 30 mm like FS said enough place to fill in original can regards

[kriegsfunker]

6 hours ago, tornfuté said:

It will be usefull for restoring  psu that are over the usual 350 -400v 

 to describe how to fill new elcos.

i guess the german proof their elcos to high value , if we consider  a 

working voltage of max 1000 v , i believe a final  isolation  value of 2.000V will  be enough for such output voltage .If we put 5  elcos 120 UF  500V in serie 

it makes 24 uf  2500v. But i remember from school time there is neccessary

to put  on capacitor a resistor  to avoid damages.What will be the value,?

120 UF size is 20 x 30 mm like FS said enough place to fill in original can regards

The resistor size depends on the voltage drop you want to achieve.   R = Voltage drop / current

[Funksammler]

I guess to ensure an equal DC voltage distribution over the Elco's in the chain, you could put a resistor in parallel to each capacitor. The 50Hz and higher frequencies will see a low enough reactance to automatically distribute equally over the capacitors. So at the 1000V you may want to limit the DC leakage to 1% of your rated current, let's assume you set the leakage at 1 mA, in which case you need 1 MOhm in total, giving 200 kOhm for each resistor with a minimum rating of 0.2 Watt.

regards,

Funksammler

[tornfuté]

Thanks FS  may be it will help  kriegsfunker if he needs to replace the HV 

capacitors , i remember i got a U100 in good cosmetic outside , but when i 

open the base the HV capacitors are explosed, guess somebody put it working and they heated and finaly explose. As a rule  never try directly a set or a psu before checking  all seems ok , check LV first  later on HV, try without

valves and then measure inside valve socket if LV is present , then HV,

add fuses  to protect the set  and caution when using U80 or U100,Na8

Sglt100  , it’s lethal voltage

 

 

 

 

 

 

 

[val]

2 hours ago, tornfuté said:

add fuses  to protect the set  and caution when using U80 or U100,Na8

Sglt100  , it’s lethal voltage

For testing PSU ordinary Incandescent light bulb in series in 230V circuit limits current

when something bad happens - i prefer it to fuses. When bulb light up you see right

away that there's a problem and it's natural property to limit current is invaluable.

https://www.vintage-radio.com/projects/lamp-limiter.html

[kriegsfunker]

All the capacitors are finally out:

 

[Funksammler]

Indeed, to test a mains power supply, use a Variac and slowly increase the voltage. You will find out if you have a problem long before you reach full voltage.

regards,

Funksammler