Krell KSL Pre Amp / Phono Board Recap

SCompRacer

Greetings and welcome to the forum!

I got the parts from a friend and Digikey.

http://www.digikey.com/suppliers/us/united-chemi-con.page?lang=en

Hope you have a desolder gun. Makes it much easier to remove caps, less chance of messing up the fiberglass circuit board. The vias pull out easily if forced. For folks who never heard the term, vias are the through hole rivet like things in the board.



Here is the photobucket link for pics.

http://s417.photobucket.com/user/scompracer/library/Krell KSL?sort=3&page=1

agfrost

That's a nice looking preamp!

SCompRacer

You're just sayin that cause you're invested...

soundfreak1

I can't speak to the Krell brand on the pre but can on "Class A pre's" I picked up a Perreaux "class A " and was blown away with the difference. Would love to listen to a Krell pre on my Krell amp. But will testify to class A pre's sounding so much better. Very nice job BTW.

SCompRacer

Thanks for the kind words! Fresh caps lets the old gear live a lot longer.

agfrost

Listening to Three of a Perfect Pair vinyl through it at this very moment.

It's goooooood.

SCompRacer

Wish I was there...how about....although MC5's Rob Tyner said it first, but the KLF used it with great enthusiasm!

And right now... right now... right now it's time to... kick out the jams, moth#f%&%!!!

soundfreak1

Did you also do the power supply upgrades????

SCompRacer

Steven, an ex Krell service dept manager who started his own biz had made me aware of updates but I did not do any. Jay could look into that though.

http://www.theservicedepartmentct.com/

agfrost

Well now you're just messing with me, Rich.

Does he have a power supply redesign, or ??

I'm not unhappy with its current performance.

SCompRacer

agfrost wrote: »

Well now you're just messing with me, Rich.

Does he have a power supply redesign, or ??

I'm not unhappy with its current performance.

It's true, there are improvements although what fun is life without messing with your friends? Details were not given, it was a send and pay to get the updates. He had some for the KRC-HR too.

soundfreak1

Can one of those power supplys be built???

agfrost

Not 100 % understanding your question, soundfreak. The power supply is part of the chassis; it's a one-box unit. Rich updated the capacitors in the original power supply. I'm sure that the Krell guy's upgrade is proprietary.

SCompRacer

The Krell KRC-HR I had used an external power supply. Be tough to reverse engineer a four layer circuit board without a schematic though. Way, way past my ability.



and they used an external PS for the external KPE phono pre amp...



diyaudio store has a power supply kit. One would have to research what voltage/amperage is needed and build to suit.

http://diyaudiostore.com/collections/frontpage/products/universal-psu

The thread...

http://www.diyaudio.com/forums/diyaudio-store/238918-v3-universal-power-supply-circuit-board.html#post3554857

soundfreak1

Yes I had read about recapping the power supply, it's quite sophisticated piwer supply from what I've read.

husafreak

Well this is all very interesting. I have a KSL Preamp/phono board and KST amplifier. Twenty Five years young! I wondered if these components age and seeing this discussion I see they do. I do not have any problems with this equipment but I would like to know that it is operating at its peak. I am handy with soldering and circuit boards. But not electronics cicuit board design. Is it as simple as desoldering the caps and matching part specs? Is it just the caps that deteriorate? I do not know how to adjust the bias on my phono stage. Any advice would be appreciated.

agfrost

Hi husafreak,

I'm not the technical expert here, I just just enjoy the fruits of SCompRacer's labors. He hasn't been around too much of late, but I'm sure he'll be by soonish to chat with you a bit.

Welcome to Club Polk. Feel free to stick around and join in the conversations, it's a nice place to hang.

Jay

husafreak

Thanks! Of course I may choose to hire out the work if someone wants it. I am still working so it may be more reasonable for me to work a few extra days than spend countless ours trying to puzzle this all out for myself.

MassimoConti

Hi everybody
thanks for subscribing to your blog
I am writing to you about the problem you have had with the KSL.
I am asking you if you would kindly give me information on how to calibrate the bias to the Phono card.
Precisely where to place the volmeter or oscilloscope probes, and what are the values.
I have already replaced all the caps on the mother board, I am waiting for the icaps for the phono board to arrive
Thanks in advance for helping me.
Massimo Conti
P.S I live in Florence, Italy

SCompRacer

Greetings Massimo! It has been so long (2013) that I cannot recall where I adjusted anything. I'm also older and am not as smart, if I were ever smart...lol. There was no schematic available for the KSL. I probed many areas and may have given pots a very slight turn to see what happened and took notes, but they are long gone. I must have thrown them out.

I'm sorry I cannot help. You might try searching/posting at diyaudio. I had received some assistance there with the KSA-250 amp and possibly the KSL.

https://www.diyaudio.com/community/

EDIT: After translating, love the Eastwood quote...

MassimoConti

SCcomRacer thank you all the same for giving me your time
Greetings from Florence
Massimo