I got a great haul being sold on Craigslist from an storage locker owned by an old amp tech, specialty unknown. One of the gems was mounds and mounds of vintage caps of all sorts! I can readily ID most electrolytics, more common poly_______ caps such as orange drops, and obvious ones like ceramic disc, mica etc... but there are a good couple dozen types I'm unsure about. I believe many of these are paper in oil, but believe some of them might be poly_______ as well. I would greatly appreciate any help in classifying their material/construction type, as well as any insight as to which ones are more or less reliable over time.
I've grouped them in this picture based on appearance and what I already know. For example, I am reasonably sure the 4 at the bottom are paper in oil caps, and shouldn't generally be relied upon. I also believe the 3 in the bottom right are dry electrolytics, of which I am unsure of their reliability. But I am completely unsure of most of the others, especially the rectangular ones, the 4 very unique ones at the top, and the cylindrical ones towards the left, bottom left and center, which seem to make up most of the haul.
Let me know if a closer picture is needed on any of these. Thanks in advance!
I've grouped them in this picture based on appearance and what I already know. For example, I am reasonably sure the 4 at the bottom are paper in oil caps, and shouldn't generally be relied upon. I also believe the 3 in the bottom right are dry electrolytics, of which I am unsure of their reliability. But I am completely unsure of most of the others, especially the rectangular ones, the 4 very unique ones at the top, and the cylindrical ones towards the left, bottom left and center, which seem to make up most of the haul.
Let me know if a closer picture is needed on any of these. Thanks in advance!
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Also seeking perspectives on the reliability of old electrolytics in general, especially can caps. I have a Heathkit C1 Condenser Checker to measure capacitance and leakage up to 500V, but I want to make sure beyond a reasonable doubt that whatever I'm using would be likely to maintain those values for many years in service.
Most of those are pretty standard old film caps (which should be ok), and some paper ones which could be leaky.
Old electrolytics must first be carefully reformed, before testing for uF and ESR, and possible reuse.
Some have rubber seals which would have degraded in storage.
Old electrolytics must first be carefully reformed, before testing for uF and ESR, and possible reuse.
Some have rubber seals which would have degraded in storage.
Thanks! I'm mostly looking for help distinguishing the usable film caps out from the rest. What are the indicators? And for the paper caps, it's my understanding that even if they're not leaky now, there's a relatively higher chance of them becoming leaky when put in a circuit - is this the case? Or is it more the case that if they were going to be leaky, they would have become that way already?
I think you can use any of the film capacitors, within their ratings. They won't normally degrade.
Most old paper capacitors I've seen has been leaky, this plays havoc with the bias of the following tube.
I personally would not use any of those very old electrolytics.
The bumblebee capacitor is often sought after by guitar amplifier builders, you may want to sell it.
http://pickguardian.com/wp-content/uploads/2014/04/Sprague-Bumblebee-Chart.pdfhttps://shop.sonnywalton.com/022or-047-uF-400v-Sprague-Bumblebee-Capacitor-Pulls-1944.htm
Most old paper capacitors I've seen has been leaky, this plays havoc with the bias of the following tube.
I personally would not use any of those very old electrolytics.
The bumblebee capacitor is often sought after by guitar amplifier builders, you may want to sell it.
http://pickguardian.com/wp-content/uploads/2014/04/Sprague-Bumblebee-Chart.pdfhttps://shop.sonnywalton.com/022or-047-uF-400v-Sprague-Bumblebee-Capacitor-Pulls-1944.htm
Bumblebee caps are notoriously leaky and unreliable and can fry valve amplifiers - chuck them... Some guitarists think the sound of a red-plating valve is better, but its not a good idea!
Yes, plastic-encapsulated paper caps will get moisture ingress in over time (especially in storage with no heat to drive it out), and increase in capacitance and leakage, and may eventually fail due to chemical deterioration, they have no place in electronics designed to last. Even hermetically sealed paper-in-oil caps will degrade slowly, paper is not immortal, but they are the only paper caps its worth keeping as the moisture can't get in. Any Rifa brand X and Y class paper capacitors will also eventually explode, they should definitely be junked. They are usually easily spotted as the transparent plastic coating will be full of cracks.
Seconded about old electrolytics - not worth the bother really, new caps aren't that expensive and should give predictable decades of service if chosen conservatively for temperature ratings.
Yes, plastic-encapsulated paper caps will get moisture ingress in over time (especially in storage with no heat to drive it out), and increase in capacitance and leakage, and may eventually fail due to chemical deterioration, they have no place in electronics designed to last. Even hermetically sealed paper-in-oil caps will degrade slowly, paper is not immortal, but they are the only paper caps its worth keeping as the moisture can't get in. Any Rifa brand X and Y class paper capacitors will also eventually explode, they should definitely be junked. They are usually easily spotted as the transparent plastic coating will be full of cracks.
Seconded about old electrolytics - not worth the bother really, new caps aren't that expensive and should give predictable decades of service if chosen conservatively for temperature ratings.