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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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24th Jul 2021, 6:55 pm | #21 |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 587
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Re: Understanding Dual Can Electrolytics
A friend told me that they called an ESR meter a "Smugometer" because in a service and repair scenario at best they can only confirm a diagnosis.
If they don't leak physically, there's no excessive electrical leakage at rated voltage, and hum or ripple on the supply, then any replacement is likely to have inferior longevity. Just my humble opinion. |
24th Jul 2021, 6:56 pm | #22 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,935
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Re: Understanding Dual Can Electrolytics
Graham's figures give you a good guide as to where readings should be at. Peak meters BTW are first class I add.
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27th Jul 2021, 10:49 pm | #23 | |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,725
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Re: Understanding Dual Can Electrolytics
Quote:
Still, before that I wouldn't have thought about measuring ESR like that. I knew what "effective series resistance" was, but only in the context of "equivalent circuits" not as a fault-finding strategy.
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27th Jul 2021, 11:32 pm | #24 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,476
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Re: Understanding Dual Can Electrolytics
The ESR meter was (and still is) a valuable tool as far as SMPS are concerned.
This became more apparent with the advent of certain satellite receivers such as the Analogue Amstrad SRD510 and Pace PRD800/900 series. Initially we wondered why they wouldn't work when the caps measured ok via more 'normal' means but worked when they were replaced, and I think it was by a man called Ray Porter in one of the TV mags that first explained what ESR actually was. Then the various technical departments caught up! and the rest was history, the Peak Atlas ESR meter being a most useful tool in the workshop around this time.
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28th Jul 2021, 9:28 am | #25 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Understanding Dual Can Electrolytics
Quote:
Peter |
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28th Jul 2021, 12:26 pm | #26 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
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Re: Understanding Dual Can Electrolytics
I wouldn't disagree. It's just that some people don't understand why the measured capacitance is higher than that stated on the capacitor. itself.
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28th Jul 2021, 12:44 pm | #27 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,203
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Re: Understanding Dual Can Electrolytics
Realising that if it fails at 2 psi, it's surely bad, can help turning them into useful instruments. Every instrument has its limitations and when the operator takes them into account, can still be useful.
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28th Jul 2021, 7:47 pm | #28 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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Re: Understanding Dual Can Electrolytics
Yes yes yes. Like a large quantity of test equipment they are only a guide and remember that many older electrolytic capacitors had a tolerance of + 100% - 10%. They are practically impossible to test with any certainty. John.
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29th Jul 2021, 1:12 am | #29 | ||
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 587
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Re: Understanding Dual Can Electrolytics
Quote:
However as the thread was intended to be I believe about the perhaps two or three electrolytic capacitors that may be found in a bog standard mid twentieth century wireless set, there's little use for anything other than method and observation: is the end swollen or leaking? Does it get hot, or draw excessive leakage current? Is there excessive ripple/hum? If yes it's time to act. Watched a guy doing a set once that had low audio gain and worse than usual bass response, (cathode resistor bypass cap). After faffing around with replacement of three resistors that were a few percent over value, and using an Armada of test equipment including a capacitance bridge, (OK), and an ESR meter he came to the same conclusions. He held up the ESR meter and announced "worth its weight in gold" I'm sure they are marvelous in their place, but experience and good fault finding technique is far more useful. What's not unusual is when an enthusiastic amateur gets hold of these wonderful pieces of test equipment but are then unsure how to translate the readings into a course of action. Regards, Greg. |
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29th Jul 2021, 6:04 am | #30 |
Octode
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,632
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Re: Understanding Dual Can Electrolytics
As noted above, when it comes to PSU filtering caps, if they don't get warm and there's no excessive ripple, they're probably serviceable. But the question is, how much ripple is too much? Is there are rule of thumb for valve equipment, say 10% of the B+ voltage? Or is it better to temporarily connect a capacitor of similar value in parallel and observe if it makes any noticeable difference (improvement hopefully) to the audible hum?
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29th Jul 2021, 10:16 am | #31 |
Octode
Join Date: Aug 2015
Location: Glasgow, UK.
Posts: 1,850
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Re: Understanding Dual Can Electrolytics
As I mentioned in my opening Post "Not sure what those numbers are telling me but more than happy to be enlightened - thanks in advance. "
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