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-   -   Old F&T capacitor pinout (http://www.diyaudio.com/forums/parts/109920-old-f-t-capacitor-pinout.html)

hihopes 11th October 2007 07:11 PM

Old F&T capacitor pinout
 
I have picked up a couple of 470uF 450v F&T caps, but I see they have 5 pins, not 2. I have downloaded some docs from F&T, but their current range has nothing that looks anything like this. The caps are marked AL - Elko, GS 800 and appear to have been manufactured in 06/88.
On the can it says "Pluspol=1". I don't speak German, but i take this to mean pin 1 is the positive pole. It also says "Minuspol/gehause nicht isoliert", which i take to mean something like "the minus pole is not isolated from the housing" Is this a correct translation?
I am also pretty puzzled as to what all the other terminals are there for, and which one/ones are -. None of them seem to be directly connected to any others. There are pins marked 1 to 4, and the fifth pin has no marking. Can anyone tell me which pins are which? I don't have a capacitance meter.

analog_sa 11th October 2007 07:39 PM

Seems quite obvious how to use it. In the absence of any markings use a multimeter to locate a pin shorted to the can and call it ground. Whichever pin exhibits any measurable and variable with time and polarity resistance with respect to ground is the positive pin. All other pins are probably there to increase mechanical stability once the cap is soldered. The 5-pin caps are common as dirt.

1= +
5=gnd

hihopes 11th October 2007 08:26 PM

That would have been great if any of the pins were shorted to the can, but unfortunately, none are, otherwise I wouldnt have needed to ask for help. I am sure these 5 pin caps are, as you say, "as common as dirt", but I have not used them before. The guy who sold them to me cant enlighten me either.
As far as I can make out, the positive pin is shown as pin 1. When I hold the pos lead of my meter on pin 1, I get a climbing reading on pins 2 and 4. On the unmarked pin, I get a negative reading that climbs slowly and Pin 3 shows no reading. With the + probe on pin 2, i get a climbing reading on the unmarked pin. Can you tell me from this what is going on?
Thanks,
William.

analog_sa 11th October 2007 10:31 PM

If it's not a multi-segment cap you should leave alone pin 2&4.

After applying some dc voltage, with correct polarity between 1 and 5 you can verify that the capacitor is charged and even try to time the rate of discharge into a resistor. You can calculate the approximate capacitance in this way.

analog_sa 12th October 2007 07:09 AM

Have these caps been in use? Seeing they're nearly 20 years old they may need re-forming. In any case if you attempt to charge them up use a resistor to limit the charging current.

djQUAN 12th October 2007 01:10 PM

pictures might help a lot. ;)

hihopes 12th October 2007 08:27 PM

The caps haven't been used. Will a 100ohm 2w resistor be suitable? What about first trying to charge with a 9v battery?

analog_sa 12th October 2007 09:06 PM

This will produce an initial current of 90mA - too much IMO. Rather keep the max current under 10mA, even at a low voltage.
Once you are certain about the polarity they will definitely need to be reformed. Something like 100k at working voltage and wait as long as it takes for the voltage across the cap to climb to full voltage - may even take a day.

In any case use caution as NOS caps can be quite unwilling to reform and would rather explode. Good luck


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