Actually all of the 10.000 uF capacitors can be considered very suspicious, after 15 years of service (warming up, ripple currents, the deal):
I was careful and quick enough to switch off the Klout before any further damage could happen. I decided that replacing all (electrolytic) capacitors would give me a fair chance of fixing this faulty Klout myself!
Plot spoiler: this turned out to be true, however a nasty problem with the voltage selector would really mess up day 1 of the revived Klout.
On this webpage hopefully you can find some helpful tips (and moral support) if you would ever need to undergo a similar operation on your Klout!
The amp boards can only be removed after removing the top and bottom plates, the transformer, and the central control board. In other words, you will have to go the whole way of de-assembly, there is no cheap way out.
Note that the power amps have some heat transfer paste that will have to be replaced as well:
The speaker terminals can be disassembled but this is not necessary:
The plastic may be worn and might break (whoops!):
Remember though, to first remove the (long) screws before trying to remove these from the back panel.
The internal power cable has to come through the back-end opening completely, to be removed:
The transformer looked strange with the internal black (oily?) fluid inside. However I have been told this might have be done, by design, to reduce vibrations and to enhance heat transfer.
Original parts list:
(diameter x height x pin spacing) 1. amp C15,16,19,20 8 times: 10.000 uF 63 V 85 C 30x46x10 2. control unit C2 1 time: 10.000 uF 63 V 85 C 30x46x10 3. control unit C3, C4 2 times: 22 uF 50V (another website refers to 100V, mine were 50V) 4. amp C9,10,22,23,24,.5,26,27 16 times: 100 uF 63 V 85 C 5. amp C12,14 4 times: 220 uF 16 VAnother website states there are '68 uF 35 V' capacitors. Well, not on my year 2000 Klout?!
I ordered these for #1:
8 x MLGOAG-080 - 10000uF 63V Mundorf MLytic AG Electrolytic Capacitor
They are taller than the original (50 mm vs. 46 mm) but will fit fine.
I ordered this one for #2:
Farnell order code 235-7382 (CAP, ALU ELEC, 10000UF, 63V, PANASONIC)
This one has a larger diameter (35 mm, which is fine) and is shorter (40 mm).
Well, this turned out to be a very unsatisfying week. No control, the tune was killed, no music!
2. A heat controlled solder iron is mandatory for this type of work, you really don't want to cook those components.
This is what the revived Klout looks like on the inside:
Notice the replacement 10.000 uF elco's on the amp boards are larger but fit fine. The ninth 10.000 uF capacitor however, is on the central control board and 50 mm would be too high there. So a different type was used for that one, check the parts list.
The fix is shown here, this nicely keeps the metal strip inside the plastic container:
But oh dear ... that huge soundstage again. Ok, I love this.
So maybe I was a bit to enthusiastic going from 'stand-by' to 'on' (which means quickly running over 'off' which is the middle of those two). And then my Klout totally died, on day one after being revived.
Some hours of troubleshooting later, I was able to pin point a flaky connection inside (!) the voltage selector switch. Likely I had created an arc and the connection was now dirty. Which is easily fixed (just switch 240V - 110V 10x without the power connected of course).
If it still sounds good to you, might as well leave it be. But I would expect at 20yrs+ replacement is worthwhile. I keep meaning to pop up a short page on acoustica about this overall, so here's a rough draft of the core content: Three things matter to the lifespan of electrolytic capacitors: ripple current, time, and temperature. The ripple current is the big one - if an amplifier runs heavily into Class A and near- maximum power dissipation all the time, this means maximum internal heating in the reservoir caps (thanks to Iripple^2*esr) and so the shortest life. But for light loads like preamps and cd players where ripple currents are small, c.1-200mA roughly, this is not usually a guiding issue, becasue light currents do not drive up the caps internal temperature wildly. Anyway, you'll typically find many new electrolytic caps are rated for 2,000 hours at 85 degrees Celcius or thereabouts - check their datasheets. You can often find 105degC rated vesions, too, and it is worth choosing these if they will fit as you'll see. Electrolytic capacitor life basically follows the Arrhenius equation, where a change of 10degC roughly doubles or halves the rate of reaction. So while a 2-or-3000hr rating is usual for capacitors at full rated temp (to the point where ESR doubles from 'new' value), the reality is rather better at lower (internal) temperatures. Suppose your cap runs at about 35degC inside a well-ventilated case, or a lightly loaded piece of equipment (preamp/cd player): Based on a rated life of 2000hrs at 85deg C that suggests a useful life around (2^[85-35/10])*2000hrs at 35degC = 2^5*2000 = 7.2yrs. - Now you can see why Naim recommend service at 7yr intervals, based on 24/7/365 use. It's spot-on for prudent replacement. Now, you'll find that caps rated at >>2000hrs at 105degC are now available at a very small premium. This might place high-quality reservoir cap replacements into the 'fit-and forget' category , with a realistic 25yr+ life at moderate ambient temps. (I like the Evox-Rifa PEH169 and PEH200 series for such things. They sound good, too. There are others of course.) Note a capacitor manufacturer's rating is to a given criterion e.g. typically, to doubling of ESR. Which may have little or no audible effect in our uses! - depending on a given amplifier's sensitivity to component values. A given or predicted lifespan certainly does *not* mean the wheels suddenly fall off! But - to pick an instance - for Naim perhaps it does make very good sense since their classic amplifier design has a slightly lower PSRR than some other designs. A bunch of caps in a preamp, which see no significant riuple current and run at constant tempeature might easily and usefully last 2-3x as long without notable degradation. All a matter of design choices and trade-offs.All credits to 'felix' on 15-11-2013, link: http://www.audio-forums.com/threads/capacitor-replacement-on-my-linn-equipment.111434/