Krell KSA 100mkII Clone

[danieljw]

Hello
I need some 1N5309 t repair my Krell KMA 100 first generation.
I live in Germany.

Regards
Piet

Hi Piet,

Here they are still available:
https://au.element14.com/american-p...&ddkey=https:en-AU/Element14_Australia/search

 

[AVWERK]

Not cheap !

 

[danieljw]

Not cheap !

It is a relatively old specialised part.
I think there is alot of different and maybe better ways to achieve 3mA current regulation. But they are very simple to use....

-Dan

 

[PMik]

Hello
I need some 1N5309 t repair my Krell KMA 100 first generation.
I live in Germany.

Regards
Piet

Piet

Better priced here:
https://www.newark.com/american-power-devices/1n5309/current-regulator-diode-600mw/dp/30C5652?


Do you happen to have the schematics for the KMA-100 ?

A couple of weeks ago i bought a pair for a reasonable price, one amp is good, the other one has an issue on the negative side of the Reg PSU board .., afics a zener went bad, everything else of the amp seems good.., by age all axial caps and the FB caps on the input/driver boards for sure needs to be changed

 

[stolbovoy]

Hello
I need some 1N5309 t repair my Krell KMA 100 first generation.
I live in Germany.

Regards
Piet

I replaced them with Semitec E-352 (https://www.mouser.com/ProductDetail/Semitec/E-352?qs=/ha2pyFadugtme7WiUbN6zhqafNAiO30INk/ohBXZLY=)

 

[RobertS61]

I've had a Krell KSA-100 Mk2 and have read (two years ago) every page of this superb tread to get to know this amp better.
Now I have a KMA-100 Mk2's (mono version) and one of the amps blew a MJE-15031 PNP driver:
https://www.diyaudio.com/forums/attachment.php?attachmentid=914727&stc=1&d=1611502772

I can of course order a new one for two dollars or so but the problem may originate somewhere else.
I have a schematic (not very pro) also (I know you like that) and I think I have the PWR202 REV B board with the blue RIFA filmcapacitor:
https://www.diyaudio.com/forums/attachment.php?attachmentid=914734&stc=1&d=1611503262
https://www.diyaudio.com/forums/attachment.php?attachmentid=914735&stc=1&d=1611503262
https://www.diyaudio.com/forums/attachment.php?attachmentid=914737&stc=1&d=1611503577
https://www.diyaudio.com/forums/attachment.php?attachmentid=914738&stc=1&d=1611503639
Maybe you have some tips?

 

[K-amps]

Its likely died of thermal stress. When I see those brown marks on TO92’s and TO220’s... that means they have been cooking at 70c or so for a couple of decades...

 

[RobertS61]

That's true, for 33 years to be exact
Not continuously of course otherwise you total electric bill for operating these vampires would be the same amount as the acquiring price of them.

So just replace them all in both amps would you advise?

 

[K-amps]

Yes please. the others will go soon as well.

 

[RobertS61]

Okay, good advise.

 

[PMik]

Did receive a notification of activities in the tread .., great!
Refurbishment of the boards is complete, so next step was to order new batch of main capacitors, should receive them on Wednesday,
8x Kemet 51000uF/100V- 20K Hours
4x Kemet 20000uF/100V- 18K Hours
Both are a notch up in capacity

I am going to relocate the boards to be placed like in the MK II version .., seems very obvious that you should not run the harness for the cooling tunnel ,so close to the speaker out like in the KMA-100 MK I

 

[RobertS61]

Okay great.

I presume you have the KMA-100 Mk1's then.
Used Kemets in my KSA-100 Mk2 also:
https://www.diyaudio.com/forums/attachment.php?attachmentid=914815&stc=1&d=1611522021

I've a bunch of large can capacitors from Levinson ML-2's, Krells, Threshold SA/1's and Conrad Johnson Premier One b and they all retained their original capacitance and very low esr wich I both measured with dedicated hardware.
So I won't replace may 12 large cans in my KMA-100's probably.

 

[fencki]

today i listened again to my krell clones...

 

[RobertS61]

They look spectacular good to me!

 

[Arick]

+1

 

[PMik]

Okay great.

I presume you have the KMA-100 Mk1's then.
Used Kemets in my KSA-100 Mk2 also:
https://www.diyaudio.com/forums/att...11522021-krell-ksa-100mkii-clone-img_0280-jpg

I've a bunch of large can capacitors from Levinson ML-2's, Krells, Threshold SA/1's and Conrad Johnson Premier One b and they all retained their original capacitance and very low esr wich I both measured with dedicated hardware.
So I won't replace may 12 large cans in my KMA-100's probably.

When I worked on the KMA-100 with an issue (Reg PSU; one shorted 470uF/100V- and one shorted Zener).., I just did not like the feel of lightness i felt on all of the main capacitors, i dont think there is much "juice" left in them

 

[RobertS61]

Okay.

Whenever I got an American amplifier older than 25 years I automatically replaced those large cans for new ones a pretty costly operation.
Now I have a British made ESR meter from Peal electronics and a capacitance meter and all the 30 or so big blue Sprague, Mallory and CDE filtercaps I have leftover have retained their initial specified values and at the same time very low ESR even those from a 1978 Mark Levinson ML-2 Class A amps.
Levinson ML-2:
https://www.diyaudio.com/forums/attachment.php?attachmentid=915325&stc=1&d=1611650488
https://www.diyaudio.com/forums/attachment.php?attachmentid=915328&stc=1&d=1611650707
https://www.diyaudio.com/forums/attachment.php?attachmentid=915324&stc=1&d=1611650488
Threshold SA/1
https://www.diyaudio.com/forums/attachment.php?attachmentid=915327&stc=1&d=1611650488

 

[Bfpca]

These vintage caps are built to a very high standard. I have repurposed some of those for amplifier builds but I have also seen them fail shortly after being put back in service. Specifically, in an aleph J amp all was ok for a month or so and then I began to have hum issues. One of the caps had lost most of it’s capacitance.

 

[PMik]

Slow progress in my KMA-100 Refurbishment.

But i did finally bench test the functional amp of the pair

Output just below onset of clipping

187W 8Ohm & 324W 4Ohm

Idle current 2.8A
DC offset 3mV

 

[Bfpca]

187w at 8 ohms with 2.8 amps bias- That must be throwing off a lot of heat!