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Old 7th July 2012, 05:27 PM   #11
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If you change 6 components and it doesn't work then you are lost.
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Old 7th July 2012, 05:51 PM   #12
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Quote:
Originally Posted by pixelphoto View Post
I intend to replace all or most of the caps on a psu.


For an SMPS you have to replace all the electrolytics and that includes any small ones too. I am not familiar with this particular PSU but electros of 0.47uf and lower are often seen. Make sure you check for any bipolar caps too as these were often fitted for small values and can not be replaced with a normal polarised cap.

These small values are just as likely to fail as more obvious candidates. The main reservoir cap on the primary side is a major failure item in many PSU's.

Unless you are used to working on these types of PSU then you need to exercise extreme caution. The primary side is live at all times irrespective of mains lead polarity and irrespective of what might or might not have ground symbols on it. In fact it is against the forum rules to elaborate and discuss these.

Be very careful. If you get something wrong then it can literally go up with a very large bang.
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Old 7th July 2012, 06:34 PM   #13
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Quote:
Originally Posted by Mooly View Post
For an SMPS you have to replace all the electrolytics and that includes any small ones too. I am not familiar with this particular PSU but electros of 0.47uf and lower are often seen. Make sure you check for any bipolar caps too as these were often fitted for small values and can not be replaced with a normal polarised cap.

These small values are just as likely to fail as more obvious candidates. The main reservoir cap on the primary side is a major failure item in many PSU's.

Unless you are used to working on these types of PSU then you need to exercise extreme caution. The primary side is live at all times irrespective of mains lead polarity and irrespective of what might or might not have ground symbols on it. In fact it is against the forum rules to elaborate and discuss these.

Be very careful. If you get something wrong then it can literally go up with a very large bang.
Under fault conditions I agree, under upgrade conditions I disagree
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Old 7th July 2012, 06:54 PM   #14
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From my vast experience of shagging more stuff than I care to mention, I would definitely say that if it ain't bust, don't fix it!
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Old 8th July 2012, 05:32 AM   #15
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Originally Posted by underwurlde View Post
From my vast experience of shagging more stuff than I care to mention, I would definitely say that if it ain't bust, don't fix it!
After 30 years of electronic experience, i am agree with you.....
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Old 8th July 2012, 06:23 AM   #16
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Quote:
Originally Posted by KatieandDad View Post
Under fault conditions I agree, under upgrade conditions I disagree
Hi K&D

The problem with old caps is that they can be well on the way to reaching a point where they will start to cause problems. In an SMPS this typically results in incorrect drive leading to overheating and quite possibly a major blow up.

The day job involved working on and analysing the failures of SMPS's (the numbers worked on over the years must be over 10,000). Not to replace all caps is false economy.

Just some general comments on these type of PSU's

A big majority of PSU failures are due to dried out caps, also dry joints on chopper and and other wound components (not exclusively but very common) and high value resistors used for start up that go high. These must be of a correct high voltage type if ever they are replaced. Another common issue (if used) are preset pots that develop a dead spot of become intermitent due to "loose rivets" or whatever mechanical method is used to terminate the resistive track. With an SMPS any fault that lasts even for a few microseconds is enough to cause a latch up with destruction of the chopper transistor.
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Old 9th July 2012, 02:06 AM   #17
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Smile Cap change update

It's been 24 hrs. since I changed ALL the caps on the psu on my modded Sony PS-1 (mdl. 1001). I've been spinning cd's all day. No smoke, flames nor explosion. Just a cooler running and better sounding cd player. Yea, no game playing here. The soundstage opened up quite a bit this afternoon, instruments has more space around them, more detail and dynamics. Just what I was hoping for.
Thanks for all the advise and info.

Regards,
Marvin

Last edited by pixelphoto; 9th July 2012 at 02:08 AM.
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Old 9th July 2012, 06:00 AM   #18
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Good to hear it all went well.
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Old 9th July 2012, 06:22 AM   #19
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Thank you Mooly.
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