Old Sikorel caps..still usable?

[Hikari1]

I recently won a pair of 33,000uf/40v Siemens Sikorel caps on ebay. I didn't realize the date code was 1992 until I got them. They look new...

Should I use them or is it an accident waiting to happen?

 

[MorbidFractal]

Elsewhere in the forum...

Old Electrolytic Capacitors Still Good . . . Genuine Science

You're welcome.

 

[AndrewT]

Reform them slowly.
Test leakage and esr.
If both are good, then you have proved they have not deteriorated.
Use them.

 

[Hikari1]

Any way to reform without a variac?

 

[AndrewT]

Just use a large value resistor.
100k with 63Vdc across it will give an initial charging/reforming current of 0.63mAdc
If you have 4 sikorels use 4 resistor and reform them all at the same time.

You could use a 50k pot wired as a VR feeding 4 off 22k reforming resistors.
set the VR high for the first 30minutes. Reset it to half value after an hour and then to around zero after two hours.
Then leave to soak for the rest of the 24hours.

 

[67339]

Hello,
After reforming they will probably work perfectly. Recently a friend of mine had his Hiraga amp checked and serviced. The original Sic Safco co38/co39 still working great. They were designed to work reliable and having a long life.
Now only very few brands available built like this.
Greetings, Eduard

 

[kodabmx]

I've bought many surplus caps from the 1970s-80s and used them as they were. I've never had to "reform" a capacitor. However, mine are all high voltage. 2200uF/385V etc. YMMV

 

[Fast Eddie D]

I have a stash of NOS caps that are probably at least 25 years old. I do a basic leakage test (I charge them up and let them sit for a week) and if they pass, I use them in less demanding applications.

So far 100% pass and zero failure rate. I've probably used about 30 of them so far, still have some on tap.

And I've seen leaky capacitors in older equipment too. If you charge them up, they collapse right away.

I do buy new capacitors for some applications.

 

[AndrewT]

I've bought many surplus caps from the 1970s-80s and used them as they were. I've never had to "reform" a capacitor. However, mine are all high voltage. 2200uF/385V etc. YMMV

try applying 380Vdc to them and see what proportion blow up !

 

[kodabmx]

None have so far. I've had some that were 10000uf 150V 170 surge sitting at 170 for months without issue, too. I guess I'm lucky. That and the caps are Phillips, Mallory etc.


Here's an example: I bought this 8 years ago at a surplus dealer for $5 and used it at 370V for 5 years 24/7 before I scrapped the power supply. Keeping it for the next project.

 

[Hikari1]

I reformed these Sikorel caps and used them in my Pass F5. And they sound well, awesome. Staggering improvement over the nippon chemi u32d that we’re in there before. Glad you guys told me to reform and use them.

 

[jlithen]

I believe the original Sikorels were supposed to work right out of the box if stored for...10y???
Or something. Very low risk for runaway.
The red caps are also pretty bomb proof.
I have barely ever reformed caps and all my NOS caps have worked fine.
Reforming at least standard 85/105C ones is a good idea if they are old.
I had one Nakamichi amp that some cap started leaking immediately in when I powered it up first time in 20y