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HiI just had an AN copper foil PIO cap go dead short and destroy an output tube. The beast rated at 630v was running at about 200 ish volts.
I aint happy. Any one else had a similar experience. I have replaced the ANs with a pair of mylar caps from my junk box and they aint half bad. Not sure if I'de by ANs again.
Follow Ups:
Todd
those were some of the ones made by jensen..The jensens sound great for the most part but this is precisely why I use the russian k40s or the vitaman Q pio caps.They sound better in most every application and they are more reliable and you pay less than 5 dollars each with shipping many times.I have to admit it was my jensen aluminum caps that got me hooked on pios but since I have so many pieces I wasnt going to use jensens in all of them so when I found vitaman Qs and K40s I was just as thrilled with the sound.
Dear Todd,Send it back to me and I shall have a look at it, it may be from a batch which had problems, but it may also be that it was subjected to either too much heat or over voltage.
The running voltage across the cap may be 200 volts. but you need to consider the start up surge, plus the ambient temperature where the cap is situated in the amplifier.
Paper in oil caps are highly sensitive to heat (and here I have to say that encasing them in copper does not help), for every 5 degrees increase in temperature their breakdown resistance drops by 10% or more.
Hope this helps.
Sorry if I sounded a bit cross but I was!
Ok Peter will send you the pair. Re operating conditions. Under a ventilated bottomless chassis and nowhere near the O/P tubes cathode resisters. HT 350 volts is rectified by a 53KU so slow start voltage at anode preceeding the caps is < 200.
My amp chassis doesn't get too warm maybe blood heat at mostAm very happy with my AN output trannies though!
where to send them?
Dear Alan,Thanks, I would get a bit cross too if it happened to me, but with small handmade items like this variability is always greater, it is part the price one pays for quality I think.
Send back to me on the address on the web site, we have recently changed the material in the caps from paper to oil filled mylar and not only is the sound better, but reliability is no longer a real issue.
"with small handmade items like this variability is always greater, it is part the price one pays for quality I think."Ummm, isn't "quality" a measure of reliability and part-to-part consistency? I would assume that you do not have six sigma capability..?
I'd rather have my capacitors be built by a robotic assembly line than human hands. More consistent, more reliable, less chance of defect and microphony. Admittedly, not as fashionable or as cool a back-story, but a cap is not supposed to make me think of an artisan laboring in a workshop, it's supposed to have a 1/wfC impedance and nothing else.
Dear MKJ,In the largely one dimensional world of mass production the measures you mention are generally the ones governing quality, and if one is making a refrigirator or toaster then they are fine as measures.
We define quality in this regard as sound quality, and whilst consistency and reliability are important measures as well, at the end of the day a specialist part or product has to be defined by how it performs within its defined brief.
"We define quality in this regard as sound quality"So how good does an amp with out of spec caps or burnt output tubes sound?
I'm reminded of the old line about Jaguar: "Every part that falls off is of the finest British workmanship."
Dear MKJ,The small percantage of caps that fail, don't sound great, that is true and as a former Jaguar owner myself all I can say is that it is sad that the genius that created the cars was not matched by an equivalent ability to build them.
The point here is that any small volume production item which attempts to expand the envelope in some respect will always suffer from more variability than large scale industrial production items made to a price, and what it comes down to in the end equation is how well it performs within its brief.
It is a very easy argument to just look at what something does not do, how about looking at what it does do well and then seek to reduce the failure rate, that is after all what originally created the cheap mass produced parts that you touted earlier once upon a time.
The Mahatma has missed the point me thinks. A capacitor is very much more than its 1/Wc and ESR and as for 6 sigma lets leave that to the anal retentives who enjoy that sort of thing
It may not have been the voltage. I have found that the AN and Jensen PIO caps are very sensitive to the thermal environment. I have not had any problems with preamp applications, but if you use them in a tube power amp they HAVE to be away from any close proximity to tubes. They will begin to develop DC leakage and eventually fail.
My experience as well.
Thanks for the info. I was a bit sceptical about the use of vegetable oil in caps. great for salads and frying but in capacitors? nah veggie oil is prone to oxidise and generally degrade. Happily I have found replacements for free in the form of Wima mylar capacitors from my junk box. These aren't as quite as sweet as the ANs but I like free!
All other coupling caps have been fine.
Same here. Cardas Caps better the AN Cu PIOs in my amp,YMMV. More affordable too!
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