Krell KSA 50 PCB

[wim]

I am talking about Fischer SK 109 heatsinks with alu plates to make a windtunnel (they are optional), 18 cm high, and sorry, i see that it is 0,3 K/W without fans.

They look pretty like the ones in the original Krells.

 

[NUTTTR]

Fans have proved AMAZINGLY valuble....
I was running 60mv bias (approx 88ma of bias = about 3.7w of dissapation per device...heatsink sat at about 58deg after 3 hrs...
I added a 12v 8cm fan running @ 9v...
Now i have 215mv bias (!) on a 2.7c/w heatsink, with fan, the heatsink is a pretty stable 48deg - i am now running 316ma of bias per device... dissapating about 13.6w/device... about 27w for the heatsink!
That's with 43v rails... just in case my maths is wrong... it's not heating the room, but considering it's running 1 set of outputs!!
Not bad! (the outputs would probably blow if i cranked it... but i'm not going to!)

Aaron

 

[VT67]

Hi Wim

Just had a quick look at Fischer's website and I think I'm gonna try to get my hands on one of these (see att)
They are even more "Krell look a like"

Cheers

 

[K-amps]

Aaron your calcs are good... but you are only getting 1.6 watts of class-A output (at an efficiency of 5.88%) rest of your output upto 100 watts is class-AB/B. What OP devices are u using?.

Good for testing though. .

 

[wim]

Yes GeWa, they look great and very "Krelly", but they are not very high i see in the datasheet, and i did not see how much K/W they are (eith and witout fan). Do you know this ratings?

 

[wim]

NUTTTR, i asume you lower the value of C105 and C106 from 330 PF to a lower value, like 33PF or 47PF? Can you tell us what brand and type the new C's have, i can not find good quality C's with that value.

 

[VT67]

Okay Wim, some technical mumbo jumbo for you.

 

[wim]

Whow, as i can see no temp. problems with these!

 

[Repute]

dhole - You missed the group buy, but if your lucky Troy might still have a couple...

His forum user id is rabstg.

Good luck!

 

[VT67]

Wim

The heatsink mentioned above costs 50€ for 1m lengts. Not all that expensive I think. Delivery is about 2 to 3 weeks.

For the 33pF caps, I'm going for silver mica.

 

[wim]

€ 50,00 for 1 meter is very cheap!

 

[Jan Dupont]

wim:

You asked earlier "why not use the original relay" for the DC protection.....
I just assumed that a relay of this age was out of production, however I have checked up on it, and have found that Omron still makes it

 

[K-amps]

I hope it is not one of the famous "Buzzing" Krell relays.....

 

[Jan Dupont]

Thats also why I asked you all which relay to use

 

[Stuart Easson]

amazing

If that price is real, someone should start a group buy.

You only need about 16"/40cm to make a ksa50 or 32"/80cm for a ksa100.

I think, maybe the price is just too good...I would expect to pay that for a foot, which would only give you 3 sides of the wind tunnel...

Stuart

 

[troystg]

Hi All-


I do not have enough sets to sell to all the requestors.

I am open to suggestions. One person suggested ebay and the proceeds go to the forum.. I like that idea and would post the results of the auction and the payment to the forum for accountability.

But other suggestions are welcome.

 

[K-amps]

Hi All-


I do not have enough sets to sell to all the requestors.

I am open to suggestions. One person suggested ebay and the proceeds go to the forum.. I like that idea and would post the results of the auction and the payment to the forum for accountability.

But other suggestions are welcome.

eBay is a very good idea, just post a link on this thread to all those who want it and they can battle it out.

 

[Jan Dupont]

Parts list update:

Please let me know the suggested values for:
R124
C105 and C106
ZD101 and ZD102

Are there other updates/corrections to the parts list ???

 

[VT67]

For C105 & C106 you can choose between 33,47 or 68pF. Definitely not 330pF.

 

[MikeW]

The 330's work. If you replace them with something to low there will be high frequency oscillation. I tried it with 22's and 33's. NFG.