Hart JLH find....please help with identity/info!!

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Would be great to get some views on capacitor choice....brands/sources/etc.
I'm aware that Ebay has been described as having a lot of 'fakes' for sale.
Audio...vs...low ESR?? (Not at all sure about this!)
Lifetime hours..varies enormously from 1000 hours to 15000+ hours...what do i need to know in this respect please!!?

Grateful for any thoughts ... :)
 
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Electrolytic capacitor "lifetime" is a specification based on continuous operation at maximum rated temperature, voltage and ripple current. In practice, a linear audio amplifier is seldom used near its maximum ratings for long enough to consider that lifetime rating other than as suggestive of better quality. Some caps certainly do need high ratings for mission critical, 24/7 duty but that isn't relevant to home audio.

Cheap caps are as low as 1,000 hour rating and some highly regarded types for audio are only around 3,000 hours. As you say, long life caps may be rated at > 15,000 hours and priced accordingly but the capacitor lifetime you're interested in is estimated in years and isn't related to continuous maximum duty. Typical, good quality audio capacitors in new equipment, begin to show their weakness at 20+ years, long enough for most owners to have lost interest and moved on to something else.

ESR (the AC equivalent of resistance) is used to rate the smaller bypass and decoupling caps. Low ESR is better but not always appropriate or necessary for all duties. This really is a matter for engineering choices rather than brand and label affinities. Throwing in higher grade caps willy-nilly is just as likely to affect sound in an adverse way as make subjective improvenents. If you want to change caps for the sake of it, use popular grades that are fitted now, in 2019 rather than old legends that are obsolete but often faked in order to milk the old 1970s-80s legends :(
 
Hi Ian...and thanks for the input...particularly on 'lifetime'!

....and some highly regarded types for audio are only around 3,000 hours. ....
Trying to ascertain what these types are...and where to get 'em here in the UK.
My local RS here in Leeds stocks Kemet...among others?
Apologies if I've overlooked a topic that may have already been covered on these pages.

My plan isn't just to be changing caps 'Willy-Nilly' BTW!!!....I've concluded (post #78) that a pair are now defunct, and must be replaced in order to move on.
 
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Kemet make a wide range of caps but the brand doesn't tell you whether the quality of a specific grade is fair for the price or you're paying for something that won't do much more than any other new cap. I haven't taken the time to look at their whole range but RS seem to stock some of their moderately priced, general purpose grades. You could also try Farnell or CPC in the UK:https://uk.farnell.com/nichicon/lls1k472mela/cap-4700-f-80v-alu-elec-snap-in/dp/8813280

BTW, no need for offence at my reference to some folk who attempt to refurbish their amplifiers. On a forum, not everything is a comment levelled at the OP but in this case, for the attention of others. Not many will be in obvious need of replacements like yourself. Some will just be curious about the indications for a recap or looking for simple ways to improve their lacklustre sound quality.

When we don't have test gear, some of us try to resolve this with blanket replacements or guesswork but often that doesn't work either and we may also remove clues as to what went wrong. That's why I raised the matter.
 
Unless your transformers are vacuum impregnated, the wiring will vibrate rubbing against each other and eventually cause short circuits between them at various places and the transformer would eventually fail. Measure the magnetizing current with the secondary disconnected, it should be around 20 mA depending on the type of transformer and the material used. If it is much higher then chuck the transformer, you have shorts in the primary. We have built transformers for industry since 1961. DC resistance is meaningless.
 
Hi Ian, hadn't taken any offence BTW....but on re-reading my post, can see the way it may have looked!:eek: Will have to be more careful in future...:D


Thanks for the Farnell link....looks like that'll be the way I go. With so much choice out there, a nudge in the right direction is really helpful.


....When we don't have test gear, some of us try to resolve this with blanket replacements or guesswork but often that doesn't work either and we may also remove clues as to what went wrong........
Hits the nail squarely on the head.....


Thanks again!!
 
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