Dear frends
I'M John from Modena, italy. I have a KSA200s.
2 month later sx channel were burned, with a nice smoke
. Despair.
With a bit of good will (I'm a repairman) I removed everything and tried the final transistors.
2 Transistors model 484024 are destroyed (short circuit). I can't found it's on the market.
Which model I can use?
The model is not equal ksa 100s. Can I use MJ21193 and MJ21194 in TO-3 metal package?
I'M John from Modena, italy. I have a KSA200s.
2 month later sx channel were burned, with a nice smoke
. Despair.With a bit of good will (I'm a repairman) I removed everything and tried the final transistors.
2 Transistors model 484024 are destroyed (short circuit). I can't found it's on the market.
Which model I can use?
The model is not equal ksa 100s. Can I use MJ21193 and MJ21194 in TO-3 metal package?
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The Krell parts are 30Mhz or similar fast variety. they were custom parts that ON/MOT made for them, not off the shelf 15024/25 rebranded. They are closer to the 1302 types in speed.
Having said that.... These seem to be different ones than the ones on the 100S model. These end with 025/024... safe to say they are 250w parts. However the fT of the 21193/4 is only 4Mhz.... Safer choice is MJL4281a types which I am sure will sound better... and they are ft 35Mhz... BUT they are not TO-3 package.... The only MOT replacements in TO-3 are slow and have lower DC gain than the 1302 types... These would definitely affect sonics.... I'd either replace the entire OP stage with the MJL4281a' types OR order a replacement from Krell.... I would not put the 15025/211xx types in that nice Krell.
Having said that.... These seem to be different ones than the ones on the 100S model. These end with 025/024... safe to say they are 250w parts. However the fT of the 21193/4 is only 4Mhz.... Safer choice is MJL4281a types which I am sure will sound better... and they are ft 35Mhz... BUT they are not TO-3 package.... The only MOT replacements in TO-3 are slow and have lower DC gain than the 1302 types... These would definitely affect sonics.... I'd either replace the entire OP stage with the MJL4281a' types OR order a replacement from Krell.... I would not put the 15025/211xx types in that nice Krell.
The best and the cheapest way for you is to get all the needed parts from one sorce and that is Krell service Dpt.
Good TO-3 transisors are also made by:
Complementary Bipolar Power Transistors for High Power Audio
but you`ll have to replace all output devices at once,and that`s costly... But these are an alternative to the motorola parts.
Good TO-3 transisors are also made by:
Complementary Bipolar Power Transistors for High Power Audio
but you`ll have to replace all output devices at once,and that`s costly... But these are an alternative to the motorola parts.
Original schema
The original schema indicate mj15024 and 15025 transistors.
For non TO-3 package is impossible to install the transistors ...
For the MG6332/3 & MG9412/13 indicated by BenY, I ask:
The gain of transistor? The curve? Difference by original? There are 8 parallel transistor in positive signal and 8 in negative, coupled by 1 ohm resistance on emitter. I mustm to replace entire bank? 16 + 16 transistors? Is a big risk ...
I Ask to krell if there have transistors to replace?
The original schema indicate mj15024 and 15025 transistors.
For non TO-3 package is impossible to install the transistors ...
For the MG6332/3 & MG9412/13 indicated by BenY, I ask:
The gain of transistor? The curve? Difference by original? There are 8 parallel transistor in positive signal and 8 in negative, coupled by 1 ohm resistance on emitter. I mustm to replace entire bank? 16 + 16 transistors? Is a big risk ...
I Ask to krell if there have transistors to replace?
Hello i have the same problem, also a broken "Krell 484002" I had a few questions about getting a good replacement. I read somewhere that te original Krell 484002 where 30 mhz and the MJ15024 only 4mhz.. Is that an issue to consider?
What brand did you use?
Did you match dem? and how dit you did it?
Dit you buy these @ krell?
My sincerely, Theo Baas
Ok, I know this is a very old post, but still relevant today. Some may be aware of a fairly recent post by an Australian tech (liquid audio) who replaced all the transistors on a ksa100s with krell provided transistors. They are marked as 15024g/25g in the photo. So krell seems to either be out of the old stock or is now recommending these as Federico had used initially. Relevant post is https://liquidaudio.com.au/krell-ksa-100s-amplifier-repair-restoration-review/. Frederico, why did you eventually go to krell for the new transistors? Just curious.
I too have recapped my ksa100s, but the power transistors seemed fine. I do, however, have a question for anyone else with this amp. Upon startup do the bias meters extinguish in unison between left and right channels ? Mine seems to have a half to 2 second lag between the channels. Half second at the top bias with a lag that increases as bias level goes down with about two seconds on the last leds.
I too have recapped my ksa100s, but the power transistors seemed fine. I do, however, have a question for anyone else with this amp. Upon startup do the bias meters extinguish in unison between left and right channels ? Mine seems to have a half to 2 second lag between the channels. Half second at the top bias with a lag that increases as bias level goes down with about two seconds on the last leds.