I've recently had problems with a BookPC and from a bit of research it appears that the PSU has two capacitors which are not up-to-spec for the job (they've inserted standard capacitors and not high speed switching ones). The end result is that after a while they begin to overheat and fail, the 12v output drops (mine reports 11.13v) and the PC suffers random reboots.
Can anyone give me the details of where I could buy these two capacitors?
I've found plenty of 2200µF/16V or 10V capacitors rated to 105°C. My main concern is the 'high speed switching' part as nothing I've ever dealt with in my basic electronics has ever required anything other than standard eletrolytic capacitors. Especially as the reason the original capacitors fail is that they are not high speed switching.
Is there a term or value I should be looking for which will tell me the capacitor is 'high speed switching'.
The only thing I can think of which would give a higher charge / discharge rate for high speed circuits, is a ceramic capacitor. Like these:
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are not classed as electrolytic though, but, they are more suitable in situations of high speed charge / discharge characteristics as they dissipate the heating effect more efficiently.
Yes, I knew I should have chosen my wording a bit better. :-)) But the only capacitors I can think of, that give the type of characteristics looked for, were ceramic. And I believe that some are classed as electrolytic and they can also be any farad rating you wish. I'll have to read my catalogues again. :-(
You do that - and when you find your Extremely High Value ceramics, please tell me where to order, I could really do with some. Especially if you can get them in *any* 'farad rating'.
Electrolytics for switch mode supplies are a real nightmare as owners of quite a few top end motherboards have found when their caps failed early.
The only ones RS do that come anywhere close are their 'Super Low impedance FA Series' from Panasonic, and they're in the process of being discontinued :-!
The only 2200uF they have is 25V but that's not a problem if you can fit it in. Size is likely to be your major problem, these are 16mm dia by 25mm long where I reckon yours will be a bit shorter. Order code it 394-844, 1.28 each + vat, min order 5, 'avail until stocks are exhausted'.
The mobo issue may be a blessing as there are now guys doing cap replacements and they will likely sell you a few caps of the right sort. This guy (homie) has a good rep but is in the states:
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quick google on the abit mobo groups gave this guy as a UK mobo repairer: snipped-for-privacy@SPAMSUXbtinternet.com . He may be able to help you with supply but I have no personal knowledge of him.
btw: High value ceramics are great for hf switchers, but the circuit needs to be designed for them, no good for this app.
Whilst I agree about the need for very high quality caps on the MOBO low loss SMPS circuits, the main SMPS is less critical. The low-ESR RS ones previously mentioned should be fine for this app, although going up a voltage rating or two (and thus physical size and current rating) wouldn't hurt. Providing you have the room... :-)
CPC also do a selection of low ESR / high ripple current caps.
a search for 'radial electrolytic esr' without the quotes and the first match at the top takes you to the required page. The one you want is under SC for type. You may have to get them from one of their distributors so give them a ring.
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