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
2200µF/16V @ SC105° (to replace 2200µF/16V @ HM105°)
2200µF/10V @ SC105° (to replace 2200µF/10V @ HM105°)
Unfortunately they only do 25V or 50V at 2200µF.
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
Is there a term or value I should be looking for which will tell me
the capacitor is 'high speed switching'.
That's good - a higher voltage rating is good. You should have
no trouble fitting them on the board, plenty of room.
I've never come across 'high speed switching' electrolytics.
They are by nature sluggish, and so aren't used in pulse
I'd go for a higher voltage rated good quality electrolytic such
as RS 127-818. They should be fine.
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:
They 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
Yeah, they'll do that ;-)
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
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:
A 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.
You can get them here http://www.vtm.co.uk /
Do 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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