experienced EEs

[JohnCU]

circuit schematic with 2 filtering capacitors, vintage 1960s/70s, would you assume them to be aluminum electrolytic?

 

[manlymatt83]

Originally posted by: JohnCU
circuit schematic with 2 filtering capacitors, vintage 1960s/70s, would you assume them to be aluminum electrolytic?

no

 

[JohnCU]

Originally posted by: manlymatt83

Originally posted by: JohnCU
circuit schematic with 2 filtering capacitors, vintage 1960s/70s, would you assume them to be aluminum electrolytic?

no

i didn't know you were an experienced EE

 

[Eli]

Specs?

And why are you asking? Just get caps with the same specs. They'll probably be better than the original components anyway.

<---- Not an experienced EE

 

[JohnCU]

Originally posted by: Eli
Specs?

And why are you asking? Just get caps with the same specs. They'll probably be better than the original components anyway.

<---- Not an experienced EE

because if they are aluminum electrolytic then they require a burn-in. if they are wet tantalum, they don't. 50 hours difference. i can't tell what they are because the circuit is sealed up with epoxy.

 

[Eli]

Originally posted by: JohnCU

Originally posted by: Eli
Specs?

And why are you asking? Just get caps with the same specs. They'll probably be better than the original components anyway.

<---- Not an experienced EE

because if they are aluminum electrolytic then they require a burn-in. if they are wet tantalum, they don't. 50 hours difference. i can't tell what they are because the circuit is sealed up with epoxy.

Hmm.. I see. What is the circuit?

More info about burning in caps?

 

[JohnCU]

Originally posted by: Eli

Originally posted by: JohnCU

Originally posted by: Eli
Specs?

And why are you asking? Just get caps with the same specs. They'll probably be better than the original components anyway.

<---- Not an experienced EE

because if they are aluminum electrolytic then they require a burn-in. if they are wet tantalum, they don't. 50 hours difference. i can't tell what they are because the circuit is sealed up with epoxy.

Hmm.. I see. What is the circuit?

More info about burning in caps?

the circuit is pretty simple, just converts AC to DC and the caps filter it. they call it a demodulator but it's a rectifier basically.

there is a lot of industry experience with aluminum electrolytic caps failing because they sit on the shelf forever and something (can't remember what, oxide something? have to go look at the report) degrades over time and you need to burn them in to find infantile failures.

 

[Cogman]

For those wondering, burn in is when you run the capacitor at a higher then rated voltage in a rated temperature.

There is no guaranteeing either way. Your safe bet would be to burn it in.

 

[JohnCU]

Originally posted by: Cogman
For those wondering, burn in is when you run the capacitor at a higher then rated voltage in a rated temperature.

There is no guaranteeing either way. Your safe bet would be to burn it in.

we consider burn-in (for circuit cards) at rated voltage at rated temperature. there is no way to burn in this component on the bench, has to be in-service burn-in. there's also no way to test the capacitors individually since the whole thing is in some sort of epoxy seal.

 

[PottedMeat]

Wait, why would a circuit with aluminum electrolytic capacitors be sealed with epoxy? Wouldn't that defeat its venting system?

What are their values?

 

[JohnCU]

Originally posted by: PottedMeat
Wait, why would a circuit with aluminum electrolytic capacitors be sealed with epoxy? Wouldn't that defeat its venting system?

What are their values?

the designer wanted to keep out moisture apparently (from the manual i have). don't have the values, they aren't listed.

 

[blahblah99]

Originally posted by: JohnCU
circuit schematic with 2 filtering capacitors, vintage 1960s/70s, would you assume them to be aluminum electrolytic?

Depends on the purpose of the circuit. For filtering, it's highly unlikely it is electrolytic as their tolerance ratings are generally bad and their capacitance over the long term changes.

My guess is the caps are either mylar or polyfilm if the circuit is filtering low-level signals.

 

[PottedMeat]

Originally posted by: blahblah99

Originally posted by: JohnCU
circuit schematic with 2 filtering capacitors, vintage 1960s/70s, would you assume them to be aluminum electrolytic?

Depends on the purpose of the circuit. For filtering, it's highly unlikely it is electrolytic as their tolerance ratings are generally bad and their capacitance over the long term changes.

My guess is the caps are either mylar or polyfilm if the circuit is filtering low-level signals.

"the circuit is pretty simple, just converts AC to DC and the caps filter it. they call it a demodulator but it's a rectifier basically."

Sounds like a power filter -> fat high value wide uF tolerance cheap aluminum electrolytic cap

 

[blahblah99]

Post the schematic.

 

[Cogman]

Originally posted by: JohnCU

Originally posted by: Cogman
For those wondering, burn in is when you run the capacitor at a higher then rated voltage in a rated temperature.

There is no guaranteeing either way. Your safe bet would be to burn it in.

we consider burn-in (for circuit cards) at rated voltage at rated temperature. there is no way to burn in this component on the bench, has to be in-service burn-in. there's also no way to test the capacitors individually since the whole thing is in some sort of epoxy seal.

Humm, not much you can really do then, other then breaking out the good ole' oscilloscope plugging the sucker in, and see if it is preforming as expected. If this is a mission critical piece then I wouldn't waste my time wondering if it will work or not, I'd just go get a replacement rectifier. If it isn't all that important, then I would run it through its paces for a couple of hours, see if it performs as expected, and cuss if it decides to blow out in the near future.

 

[JohnCU]

Originally posted by: blahblah99
Post the schematic.

it's proprietary information, can't do it. it's about as simple as you can imagine though. a few diodes and 2 caps.

 

[JohnCU]

Originally posted by: Cogman

Originally posted by: JohnCU

Originally posted by: Cogman
For those wondering, burn in is when you run the capacitor at a higher then rated voltage in a rated temperature.

There is no guaranteeing either way. Your safe bet would be to burn it in.

we consider burn-in (for circuit cards) at rated voltage at rated temperature. there is no way to burn in this component on the bench, has to be in-service burn-in. there's also no way to test the capacitors individually since the whole thing is in some sort of epoxy seal.

Humm, not much you can really do then, other then breaking out the good ole' oscilloscope plugging the sucker in, and see if it is preforming as expected. If this is a mission critical piece then I wouldn't waste my time wondering if it will work or not, I'd just go get a replacement rectifier. If it isn't all that important, then I would run it through its paces for a couple of hours, see if it performs as expected, and cuss if it decides to blow out in the near future.

that's what i figured, thanks.