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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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Old 24th Jul 2021, 5:55 pm   #21
G.Castle
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Default 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.
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Old 24th Jul 2021, 5:56 pm   #22
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Default 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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Old 27th Jul 2021, 9:49 pm   #23
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Default Re: Understanding Dual Can Electrolytics

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Originally Posted by G.Castle View Post
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.
About 15 years I was introduced to one of Bob Parker's ESR meters and used it to locate the cause of many S.M. power supply problems by testing the electrolytics in situ

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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Old 27th Jul 2021, 10:32 pm   #24
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Default 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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Old 28th Jul 2021, 8:28 am   #25
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Default Re: Understanding Dual Can Electrolytics

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In some respects modern capacitance meters are one of the worst things ever invented. People don't seem to understand that capacitors fail because of electrical leakage which can't be checked except at the full working voltage.
In some ways modern capacitance testers work quite well because if the capacitor reads significantly high in value you know its leaky. There are lots of old Meggers around and they test quite well for leakage at high voltage.

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Old 28th Jul 2021, 11:26 am   #26
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Default 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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Old 28th Jul 2021, 11:44 am   #27
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You wouldn't test a steam boiler designed to work at 200 psi with a 2 psi hydraulic test would you?
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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Old 28th Jul 2021, 6:47 pm   #28
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Default Re: Understanding Dual Can Electrolytics

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In some respects modern capacitance meters are one of the worst things ever invented.
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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Old 29th Jul 2021, 12:12 am   #29
G.Castle
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Default Re: Understanding Dual Can Electrolytics

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Quote:
Originally Posted by G.Castle View Post
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.
About 15 years I was introduced to one of Bob Parker's ESR meters and used it to locate the cause of many S.M. power supply problems by testing the electrolytics in situ

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.
Yes, and I'd agree that is an excellent use for such a piece of test equipment I'm sure.

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,
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Old 29th Jul 2021, 5:04 am   #30
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Default 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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Old 29th Jul 2021, 9:16 am   #31
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Default Re: Understanding Dual Can Electrolytics

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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.
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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