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Old 13th January 2006, 05:38 PM   #1
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Default krell ksa 50 capasitor help needed

Hi Folks

I am looking to replace the 4 40000 uf 75vdc capacitors in my old krell ksa 50, but I am having no joy searching the internet.

Do I have to use exactly the same spec of components. if not what can I use and where can I get them.

please go easy on my as mechanics is my trade not electronics, I do understand V=IxR if that helps.

The amp seems to have difficalty drive ,bias and offset all check out on my meter also it heats up as normal.

it sounds as if you are feeding it a signal with no bass and lots of treble.

Im realy stumped on this one and any help would be most welcome.

Kindest regards:
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Old 13th January 2006, 06:54 PM   #2
jaycee is offline jaycee  United Kingdom
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Are you absolutely sure this is the power supply capacitors ? This could be a problem with the capacitors in the feedback path.

As for the power supply capacitors, you can use any similarly sized capacitors that have 75V or better voltage rating, and a similar amount of capacitance. While i've not seen the KSA 50, Krell usually use screw terminal capacitors. 47000uF 80/100V should work provided they physically fit

edit: Apparently the KSA 50 has 50V power supply rails. If that's the case, 63V rated capacitors will be fine.
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Old 13th January 2006, 07:02 PM   #3
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Yes, the symptom of supply caps going bad is usually hum breakthrough and lack of response at the bottom end. Which version of the Krell is it?
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Old 13th January 2006, 07:34 PM   #4
jaycee is offline jaycee  United Kingdom
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As for where to source parts - both Farnell and RS have these types of capacitor

http://uk.farnell.com
http://rswww.com
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Old 13th January 2006, 07:49 PM   #5
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Thanks guys.

The amp is a ksa 50 mk1 very early ,it shares a lot of parts with the orijinal ksa 100 so I suppose krell just used components at hand to build the 50.

I have found a few caps rated about 47000 100vdc the same size and also a few at 37000 uf 63 vdc.

Their is no bottom end to the sound things went pear shaped ages ago when I attempted to adgust the bias and managed to snap of a roc cap 16v 1000uf next to the bias pot. so I replaced all 4 with black gate ones then set up the bias and off set .

I keep on telling my self that I should leave things alone, but I cant help it, i HAVE TO TAKE THINGS TO BITS ETC.

Im not 100% sure the caps are dead people are suggesting that they may be the problem as the amp is 20 years old.

Any thoughts?
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Old 13th January 2006, 07:55 PM   #6
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Resetting bias and offset is not bad, more like common sense.

If you have a MKI, and the big cans are the original ones, you can be sure that they are causing it. Or near death.
+20 years and those temperatures is a killer combo.
Only question i have is whether you replaced the 16V caps between the feedback resistor and ground in the right position, +and - where they belong ?
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Old 13th January 2006, 08:08 PM   #7
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If I had the 16v caps the wrong way round could this be causing the problem.

The amp was fine before I started to fiddle with it, do caps sudenly give up of is it a gradual process.

sorry for the silly questions but if I dont ask I will never now.

Cheers
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Old 13th January 2006, 08:11 PM   #8
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Sorry I forgot to add for pinkmouses benifit there is no hum just a lack of bass/lower mid
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Old 13th January 2006, 08:12 PM   #9
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Quote:
Originally posted by beckypumps
If I had the 16v caps the wrong way round could this be causing the problem.
Yep.
in practice there is less than 1 volt across the series 16v caps.
Hooking them up the wrong way need not kill them, but the effect is peculiar.
I would change the big ones just the same, there should be little left in them.
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Old 13th January 2006, 08:14 PM   #10
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That's ok, a few of us have had a little practise with Krells around here!

BP, can you take a pic of the boards so we can see what you've done?
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