KRELL 484081 and 484002 output transistors remplaces codes. HELP!!!

[fepablo]

HI, my name is Federico, from Argentina. I have a Krell KSA 100S Amplifier (year 1993). I remplace all capacitors and i find two output transistors broken. Are KRELL 484081 and 484002, do you have the motorola number to remplace.

Thank you

Federico Rodriguez.

 

[QSerraTico_Tico]

HI, my name is Federico, from Argentina. I have a Krell KSA 100S Amplifier (year 1993). I remplace all capacitors and i find two output transistors broken. Are KRELL 484081 and 484002, do you have the motorola number to remplace.

Thank you

Federico Rodriguez.

Hello Frederico,
Here they are:
http://www.diyaudio.com/forums/showthread.php?postid=493381#post493381
Unfortunately the parts are discontinued for the general public.
Perhaps with some creativity you can use the corresponding plastic case MJL types that are available.
Or the lower bandwith MJ21193 and MJ21194 in TO-3 metal package as your in your Krell.

 

[AndrewT]

Hi,
1993 KSA100s using 150W high speed output BJTs.
Is the 100s the same as KSA100mk2?

That never came up in the 100Klone thread!!
I was under the impression that these ClassA Krell's used MJ15003/4 as outputs. These 250W devices cope with the heat much better.

 

[fepablo]

Hi Guys, thanks for all.

There are a few photos od my Krell KSA 100s. Manufactured on 1993. Each channel have a 9 Krell 484081 and 9 Krell 484002, then each channel have 18 power transistors, 36 in all Krell. I have broken only two Krell 484081 on one channel. What I must to do? Only change those two? use MJ15003 or MJ21194 ? Or change all the transistors of the channel?

Thanks Again.

Federico Rodriguez.

 

[AVWERK]

You could get away replacing all with mj15024/15025 T0-3,s I would imagine.

Regards
David

 

[Chartal]

Is the 100s the same as KSA100mk2?

I think the 100S have the "sustained plateau bias"

 

[AndrewT]

Hi,
I think the two transistors out on their own are the drivers.
The other sixteen are an 8pair output stage.
I suspect that the 8 in each pair are matched.
If the drivers have gone then replace with individual transistors.

I cannot see how a singleton among an 8pair could fail and leave 7 working.
But if one of the 8 has failed then I think you must replace all 8 with a matched set.
Will Krell supply a matched set?
Or will they insist on $$$$$ for an approved repair.


Let's hope it's the drivers.
But, don't use a slow driver with fast outputs.

 

[fepablo]

The KRELL is WORKING!!!!!

I replace the 3 x Krell 484081 with 3x MJ15024 and the Krell 484002 with MJ15025. All transistors are from output stage. Krell sells the transistors orginal´s $15 each.
Also replaces all nichicon capacitors that are destroyed by siemens capacitors.

Thanks You.

Federico Rodriguez.

 

[AVWERK]

Told you so 🙂

 

[Leolabs]

Love the pics,fepablo!Show us more.😀

 

[AndrewT]

The KRELL is WORKING!!!!!

I replace the 3 x Krell 484081 with 3x MJ15024 and the Krell 484002 with MJ15025. All transistors are from output stage. Krell sells the transistors orginal´s

if the replacements are 15024/5 and they are working correctly then the original 484081/002 cannot be equivalent to 3281/1302. They must be equivalent to some other type.

 

[QSerraTico_Tico]

if the replacements are 15024/5 and they are working correctly then the original 484081/002 cannot be equivalent to 3281/1302. They must be equivalent to some other type.

How long will it work?

 

[Jozua]

How does it sound?

Hi

Do you detect a sound improvement after the change.

I have a similar amp-KSA200s which I find average sounding compared to other class A amps. I am beginning to wonder if it will sound better if one replaces some of the caps on the PCB with better caps ?

Any comments ?


Jozua

 

[fepablo]

Hi guys. The original replaces of 484081/002 are 3281/1302 100% sure, but they are discontinued. The 15003/4, 15015/14, 15024/25, 21193/94 are very similar family of transistors. In the ECA VRT manual, MJ15015 is a direct replace of MJ3281, but i dont use this because he have 180w and the MJ15024 have 250w like the 3281.

The sound is better, i replace transistors of one channel, caps of both and work same the two channels. I have a Martin Logan Sequel II Speakers.

I use the amp few night for many ours without problems or high temp. I attach more pics of the process and my other baby, Marantz 2500.

 

[AndrewT]

Hi,
the 3281 is very different from those others. They are not equivalent.

The gain higher
The gain droop @ high current is lower
The speed is higher
The SOAR varies between types
The power and current ratings are different.

I still think you should have bought a matched set.
I hope this modification works out OK.

 

[K-amps]

Compared to the 15024/25, Better match would have been 21193/4/5/6, or even 15003/4.

I never liked the highs and mids on the 15024/25 but they had killer bass...

 

[AndrewT]

Hi,
any one else want those half megabit pics removed?
They really slow down the page load on my broadband 500kb limited line.

 

[Jozua]

Caps

Fepablo

I have recently replaced my Krell 100 watter main Sprague caps and the improvement was very impressive. Faster and tighter bass. I got mine from Mouser.

I suggest that you do the same as that amp is about 10 years old and the caps have most likely deteriorated in time.

Regards

Jozua

 

[djk]

"MJ15015 is a direct replace of MJ3281"

Totally wrong, just look at the data sheets.

 

[fepablo]

Hi Friends, finally, 2 years after, i buy the original transistor at Krell.

Thanks Federico.