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Mf rating ok?
Mf rating ok?
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Old 17th April 2019, 07:39 PM   #1
XsamuraiX is offline XsamuraiX  United Kingdom
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Default Mf rating ok?

Just tested 2 large 22000uf caps from my amp and one is coming back as 19000 and the other at 20000. Some lil swelling on top too.

Are they still ok? Or time to change them?
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Old 17th April 2019, 07:56 PM   #2
nigelwright7557 is offline nigelwright7557  United Kingdom
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Electrolytics tend to come with up to +/- 20% tolerance value so they are well within spec.
Unless they are really old I would leave them.
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Old 18th April 2019, 10:21 AM   #3
DF96 is offline DF96  England
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The swelling may indicate a problem. The capacitance value is well within tolerance so is no problem.
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Old 18th April 2019, 10:29 AM   #4
Mooly is offline Mooly  United Kingdom
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Mf rating ok?
If the swelling is occuring in the actual aluminium can then its probably an indicator that all is not well. If its a plastic cap secured by the shrink wrap outer that is distorted then its probably normal.
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Old 18th April 2019, 10:41 AM   #5
XsamuraiX is offline XsamuraiX  United Kingdom
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It's the plastic with the metal top.

Just eliminating parts as my Pioneer AV amp powers up but rarely the speakers work.

Onto the FETs and transistors then...

1 quick question, the FETs/transistors that have 4 pins, what are those? Regulators?

Last edited by XsamuraiX; 18th April 2019 at 10:44 AM.
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Old 18th April 2019, 03:50 PM   #6
Mooly is offline Mooly  United Kingdom
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Mf rating ok?
Maybe, maybe not... post a picture of that part of the circuit and we'll identify them for you

Random speaker operation could be something as simple as a dry joint somewhere, perhaps causing a missing rail or causing a DC offset that prevents the relay closing.
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Old 19th April 2019, 11:12 PM   #7
XsamuraiX is offline XsamuraiX  United Kingdom
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Ok, here are the pictures.


I have had a look at the solder joints, a few do look cracked (got that circle crack inside the solder joint) and some look a much deeper shade of gret to the rest.


The pics are the mosfets along with the things next to the, and the other side, both taken from the amps amp output stage?



The other pics are what I do not know what they are, both seem to have a lil burnt section to the underside.


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Old 20th April 2019, 06:45 AM   #8
Mooly is offline Mooly  United Kingdom
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Mf rating ok?
I think I can make out IRF9340 on the board which means they are FET's. The four connections are external to the device and so you would have to look at the circuit diagram to see how they are configured. I would doubt they are the problem in any case.

All suspect joints need resoldering, taking care not to cause any accidental shorts anywhere.
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Old 20th April 2019, 03:35 PM   #9
XsamuraiX is offline XsamuraiX  United Kingdom
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Ok Mooly. The 2 pin are rectifiers or something?
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Old 20th April 2019, 05:29 PM   #10
Mooly is offline Mooly  United Kingdom
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Mf rating ok?
Well the IRF FET's have 3 pins (G,D and S) and so I'm assuming they are using the tab of the device to access the 'drain' connection as the tab is electrically connected to that middle pin.
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