How will I know when a Krell KSA-80b needs to be recapped?


How will I know when a Krell KSA-80b needs to be recapped?
cocopah
Great amp but getting old now over 14 years, depends on how many turn on cycles it’s had, but I would do them.
You can get say Nichicons same voltage and maybe even more micro farads for around $100 each, you need 4 of them. Make sure the diameter (to fit the mounting clamps at the bottom) and height (so it doesn’t touch the lid) is the same. If your handy and know + from - you could do them your self no soldering, everything is bolted, in around an hour.
http://www.audiotecnico.it/riparazioni/riparazioni_K/KRELL/KRELL_KSA80/immagini/KRELL_KSA80_power.JPG

Cheers George
PS: there are also a few other smaller electrolytic caps around the input/driver board that should be done also at the same time. 

Cheers George
If you hear a 60 hz hum and the amp sounds soft on the low end, then its time for replacement. If not -- and the amp sounds normal with no visible damage or bulging -- the caps are fine and whether you replace them at that point is up to you. Just be aware when you send in an old amp with crowded boards for recapping, other parts tend to get replaced that are in the way, which is a factor why these repairs run in the three figures.


14 years isn't too old yet if it's been always used.
I'm pretty sure the KSA-80b is more than 14 years old. It's probably closer to 25-30 years old.
Yeah, the KSA 80 first came on the market in 1987 or 88, as that's when I bought mine, so I'd say it's in the 25 year old category.  Really nice amp; it might be ready for a recap or tuneup, but it would be worth the price, as there is not much in that price range I have heard in solid state amps that sounds better or can drive difficult loads as well.

^The KMA 160 mono versions of these lovely amps are amongst my personal all time favorites.

Krells are known to be expensive to maintain, but for those that appreciate them, it's well worth it.

This may or may not apply to the Krells but I was told a sign of electrolytics reaching the end of life is you can hear the capacitors make a faint sound when the amplifier is turned off. My old Adcom does that. The noise lasts only a second or so and it’s hard to describe but it is audible if you listen carefully. It almost sounds like you can hear the capacitors discharging. Just something i had read when a similar question was asked in the Adcom circles.

25...30 years, you don't need to really know when to recap. if it works, than you can decide weather you like the performance or not.

regardless, recapping old amp will have similar effect of the new strings on guitar -- fresh and crispy sound. also i would replace output transistors as they also tend to become noisy within same period of time.

https://en.wikipedia.org/wiki/Capacitor_plague
randy-11, it's when capacitors are completely shot. less likely the amp would power up or powering up this amp is unwanted.

You know when you "need" to recap the amp when:

1.  The caps failed and the amp doesn't work anymore.

2.  The caps show signs of imminent failure.  i.e. bulging capacitors, or sound quality is failing as a result of failing caps.

These are the only time one "needs" to recap the amp.

Any other cases are speculative theory.  If the amp is working, and there is no sign of imminent failure, then you don't "need" to do anything but sit and listen and enjoy.

Preventive maintenance is a good thing, but not absolute in this case.  You can budget for the cap replacement and do so at your leisure.  Or, listen for ten more years with no issues.

A lot depends on how hard the amp was driven (used) in the past. 

I would just enjoy

I don't know from personal experience, but I visited a quite reputable hi-fi repair shop in Nashville, TN and they said don't ever recap until they are physically leaking.  

Recently bought a 20 year old krell KAV500, worked fine for couple weeks, now I hear popping sounds from the amp while it's on and even after it's been off for several hours. It works well otherwise, full power to all 5 channels. Sound lasts less than a second and I hear them about once an hour. I was told the unit was recapped priror to purchase. Is this a cause for concern ? 
A technician and/or factory trained person will bench test the unit
and check to see if the unit falls with in the factory spec.  If it fails to reach the numbers, then recapping and replacement diodes... etc will be called for.  
All companies will bench test wether it's off the assembly line or
in for an upgrade.  This is just standard quality control.  If your Krells
sound fine to you then why spend the money on new caps that will have
to go through the break in period?
(thats if you can still get the same components)
The hotter an amp runs the faster the caps will deteriorate. If you have owned it since new you can guess how many hours are on it. If not things like heat-sinks turning from black to purple or even lighter would show lots of hot hours. A tech can look at the ripple on the caps and see approximately what shape they are in. Personally I would not like caps leaking in my classic Krell ever. I would have it looked at if you are unsure of condition.

Don S