Looking for Krell KAV-400Xi schematic / service manual

[richloh]

Oops ... thanks ! Indeed foolish of me and will rotate vents above pcba as designed 🙏🙏

PS: guess I now know why I change the 12 cover screws to Philips head ones 😅

 

[richloh]

Hey everyone, love the thread on this as I have one of these and will be going through it to recap it as well. For those in need, I have the full schematic for this amp. Sadly it isn’t a digital copy, I only have it printed out on large 11x17 sheets and there are like 20 pages. So not sure the best method of getting a good copy onto the site.


Dan

Hey Dan, how is your journey so far ? As you dun even have to spend on outside repair shop to recap, I strongly recommend you to do so and do consider same high temp hybrid polymer ones and upsized mundorf caps.

Cheers.

 

[Peterz116]

I think it's als time for a recap here, I think. No problems at low volume but distortion when it plays a little louder. Are the little ones in a bad shape as well, did somebody measured them? Thanks.

 

[huggygood]

The architecture of this amp is truly an aberration.
I am really surprised that some of them did not set themselves on fire.

 

[gogg]

Change ALL capacitors !
In my 400xi, ALL were measured moderately to severely bad.
It was a timebomb. Now it is as new.
No signs of overheating in the past.
Clean the PCB professionally.
Long story short: do the total refresh if you want to use it for another 20 or so years.
It's worth it !
At least it is to me.

Cheers!

 

[gogg]

Now, looking at your picture, the PCB doesn't look good. Not shure how much damage was done. Im not a professional technician.
I paid the professional to do mine.

 

[Peterz116]

You're right, the pcb doesn't look very appealing, but I think it's mainly elco juice..

 

[Peterz116]

To whom it may concern. Schematics anyone?

 

[richloh]

Elco juice ? Think (and hope) just dust due to open ventilation and mentioned distortion seems to indicate cap issue that a bit of cleaning (before recap) to know all ok and then recap will be fine ... like me was and do keep us posted on expected good news. Cheers. 🤞🤞

 

[Peterz116]

So finally did it, removed the 72 caps and replaced them all. No more SMD, Nichicon all the way and 4x15000µF Mundorf in the power section. The 2x3300 for the preamp are a bit bigger than the originals (35V -> 50V), they didn't fit under the board anymore, I had to move them to the side. Result: no more distortion, even at higher levels, improved dynamics and placement. Took me around 8 to 10 hours, very happy with the results!

 

[Peterz116]

..and around €200 for the new caps.

 

[richloh]

Cannot think of any better input coupling caps than Nichicon ES bipolar that we are both using .. refined, clear and yet organic as well as available cheaply. Only issue is that it is 85c rated and not 105c that I wish for to be used for all new cap replacement in this rather hot amp ... but changing in another 5-10 yrs will not be too difficult since on top preamp pcba 🥳🥳

 

[levinson mark]

To whom it may concern. Schematics anyone?

Thank you for sharing. Do you have the circuit schematic of Krell KAV-280p? Can you share it?

 

[Peterz116]

Can't help you with those, no. I got mine from Krell directly, just asked nicely..