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In circuit capacitor testers advice please.
In circuit capacitor testers advice please.
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Old 14th October 2017, 05:21 PM   #21
soul music is offline soul music  United Kingdom
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Why no case for the GM328? Surely that's asking for trouble with short circuits and breakages
Please ignore above, Just found there are cases on Ebay

Last edited by soul music; 14th October 2017 at 05:28 PM.
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Old 21st October 2017, 10:01 AM   #22
soul music is offline soul music  United Kingdom
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Regarding in circuit capacitor testers, I can appreciate from the advice above that testing capacitors in circuit is not always a good idea but Amazon keep emailing me with capacitor testing products. One such is the Atlas ESR70 which claims to automatically discharge capacitors in circuit when testing and gets positive reviews. Atlas ESR70: Replacement Range Hood Knobs: Amazon.com: Industrial & Scientific
So my question is can an in circuit capacitor tester still be a useful device that MAY find that one dud capacitor and POSSIBLY save time and hassle removing capacitors?
Regarding my boombox, perhaps I should start another thread on that under analogue audio and keep this thread for advice for testing capacitors in circuit?

Last edited by soul music; 21st October 2017 at 10:05 AM.
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Old 21st October 2017, 12:12 PM   #23
soul music is offline soul music  United Kingdom
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Default Ferguson 3T18 boombox stopped working?

Hi, I have a 1980's boombox that suddenly stopped working. My partner was listening to it at the time, apparently it made a very loud buzzing noise for about a second then nothing. Now when I switch it on the speakers make the usual popping sound as it powers up and the lights still work and the tape still goes round RR, FF etc... So I suspect the problem is on the audio board? I bought this boombox as spares or repair on Ebay a few years ago and it was displaying all the same symptoms as it is now that it is not working again ( I had it professionally repaired at the time but the guy who fixed it unfortunately no longer does repairs ) . I don't know what he did but one thing I do know he did was replace the ceramic capacitor (picture with blue arrow with an electrolytic capacitor (picture with black arrow)), is it likely that this capacitor has failed again due to a weakness in the circuit or is it likely something else (I was told on another thread where I mentioned about this boombox (under equipment & tools section In circuit capacitor testers advice please. ) that the amplifier chip may have fried. Any ideas?
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File Type: jpg inside ferguson arrow 3t18 010.jpg (693.5 KB, 66 views)
File Type: jpg inside ferguson black arrow 3t18 018.jpg (335.4 KB, 65 views)
File Type: jpg inside ferguson 3t18 007.jpg (682.2 KB, 65 views)
File Type: jpg inside ferguson 3t18 011.jpg (674.5 KB, 64 views)
File Type: jpg inside ferguson 3t18 004.jpg (614.4 KB, 25 views)

Last edited by soul music; 21st October 2017 at 12:55 PM.
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Old 21st October 2017, 01:15 PM   #24
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Check the voltage regulators.
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Old 21st October 2017, 02:10 PM   #25
Mooly is offline Mooly  United Kingdom
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In circuit capacitor testers advice please.
My own personal opinion is that a capacitance tester would be just about bottom of the list of test equipment to own.

If the result appears good do you take that on trust ? and if its bad, is it bad because of interaction with other components.

What is the test voltage and current ? It is easy to degrade (degrade... not destroy or make non functional) sensitive semiconductor junctions by applying unknown reverse polarity test voltages.

I would say a good cap tester is more of a luxury and something to be used for work other than faultfinding.
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Old 21st October 2017, 02:46 PM   #26
soul music is offline soul music  United Kingdom
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Quote:
Originally Posted by JonSnell Electronic View Post
Check the voltage regulators.
I am only a novice and not sure how to do this but the boombox has a 12v DC input and I tried running from a 12v DC power supply just in case the problem was caused by the inbuilt 240v power supply unit. The symptoms are the same with the 12v supply minus the mains hum.
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Old 21st October 2017, 10:58 PM   #27
kevinkr is offline kevinkr  United States
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In circuit capacitor testers advice please.
Starting two threads on the same topic is a violation of forum rules. This thread will be merged with the original. Send me a PM if you want the combined thread renamed and moved to a more appropriate forum.
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Old 22nd October 2017, 02:59 AM   #28
anatech is offline anatech  Canada
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In circuit capacitor testers advice please.
Hi soul music,
It does sound like you have a power supply problem. However, if t was being played loud at the time, a blown output chip is equally likely.

Just in case you haven't heard it enough, you can not reliably test capacitors in circuit! I own and use an expensive LCR meter by Hewlett Packard. It does not test capacitors in circuit either despite being a few thousand dollars with levels adjustable down to 50 mV.

And one for all you happy in circuit testing people ... ESR is not what you need to test! The important characteristic is called dissipation, or the opposite of "Q". These values change with frequency in case you needed to know. I have 4 test frequencies that pretty much covers the audio range.

Huntron trackers are designed to compare two circuits against each other. You make a measurement of a known good circuit, then test the defective one. You are looking for the same "picture".

The other acceptable type of really good capacitor test is done on a capacitance bridge. No, they don't measure ESR either. They do measure "Q". The capacitance bridge does not test capacitors in circuit.

You need a GOOD meter, and an oscilloscope to troubleshoot. Not a whiz-bang "capacitor checker". Save your pennies for something that matters. Even a soldering station would be a good purchase. A digital display model can be had for ~ $100 or thereabouts. A "hobby iron" (used to call those wood burning irons - seriously!) is the greatest threat to equipment.

I hope that helps you in some way.

-Chris
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Old 22nd October 2017, 03:04 AM   #29
PedroDaGr8 is offline PedroDaGr8  United States
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Quote:
Originally Posted by anatech View Post
Hi soul music,
It does sound like you have a power supply problem. However, if t was being played loud at the time, a blown output chip is equally likely.

Just in case you haven't heard it enough, you can not reliably test capacitors in circuit! I own and use an expensive LCR meter by Hewlett Packard. It does not test capacitors in circuit either despite being a few thousand dollars with levels adjustable down to 50 mV.

And one for all you happy in circuit testing people ... ESR is not what you need to test! The important characteristic is called dissipation, or the opposite of "Q". These values change with frequency in case you needed to know. I have 4 test frequencies that pretty much covers the audio range.

Huntron trackers are designed to compare two circuits against each other. You make a measurement of a known good circuit, then test the defective one. You are looking for the same "picture".

The other acceptable type of really good capacitor test is done on a capacitance bridge. No, they don't measure ESR either. They do measure "Q". The capacitance bridge does not test capacitors in circuit.

You need a GOOD meter, and an oscilloscope to troubleshoot. Not a whiz-bang "capacitor checker". Save your pennies for something that matters. Even a soldering station would be a good purchase. A digital display model can be had for ~ $100 or thereabouts. A "hobby iron" (used to call those wood burning irons - seriously!) is the greatest threat to equipment.

I hope that helps you in some way.

-Chris
The Der EE DE-5000 measures Q, D and ESR. For low inductance and ultra low ESR parts, such as those used in high freq SMPS, having the D function at 100kHz is really useful for testing capacitor health. That being said, i entirely agree that here are other areas which are a better value for spending $100.
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Old 22nd October 2017, 03:26 AM   #30
anatech is offline anatech  Canada
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In circuit capacitor testers advice please.
Hi Pedro,
The HP 4263A tests impedance as well, and phase angle too. With all that available, still the most useful information is capacitance and D. Phase angle is related to D and Q, so the measurements are similar information presented differently.

-Chris
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