Hi ilimzn,
I first I want to clarify that I do not know about electronics but I really want to save my 20 yeras old amp.
I blew up a channel of my Conrad Johnson Sonographe SA-120 amp and have been looking for ways to repair it. I was advised to check the mosfets numbers at the output stage: they are J115 and K405.
After doing some research I found that they are the same used for the Marantz PM-94 (which was made around 1988 like my sonographe) and that they are discontinued.
Anyway, I found this post you made last year:
"K405/J115 are not lateral FETs. They are a variation of a trench MOSFET, which is in itself a variation of a vertical MOSFET. It is especially made to have a low treshold voltage, so in this way it is similar to the lateral MOSFETs, but this is where the similarity ends. The gm is (much) higher, and the tempco is that of a vertical MOSFET, positive - it needs a bias servo.
K405/J115 have been out of production for a number of years. K1530/J200 are commonly used as replacements, although they have a higher Id rating and proportionally higher Ciss."
My question is: what are the implications of the higher id rating Ciss. Can I just replace the msofets without making any other modification to the amp?. Should I also change the other channel's mosfets.
You seem to know a lot about this and I would appreciate your help very much.
Regards
Antonio
I first I want to clarify that I do not know about electronics but I really want to save my 20 yeras old amp.
I blew up a channel of my Conrad Johnson Sonographe SA-120 amp and have been looking for ways to repair it. I was advised to check the mosfets numbers at the output stage: they are J115 and K405.
After doing some research I found that they are the same used for the Marantz PM-94 (which was made around 1988 like my sonographe) and that they are discontinued.
Anyway, I found this post you made last year:
"K405/J115 are not lateral FETs. They are a variation of a trench MOSFET, which is in itself a variation of a vertical MOSFET. It is especially made to have a low treshold voltage, so in this way it is similar to the lateral MOSFETs, but this is where the similarity ends. The gm is (much) higher, and the tempco is that of a vertical MOSFET, positive - it needs a bias servo.
K405/J115 have been out of production for a number of years. K1530/J200 are commonly used as replacements, although they have a higher Id rating and proportionally higher Ciss."
My question is: what are the implications of the higher id rating Ciss. Can I just replace the msofets without making any other modification to the amp?. Should I also change the other channel's mosfets.
You seem to know a lot about this and I would appreciate your help very much.
Regards
Antonio
A Sanchez said:
Antonio,
I have routinely changed K405/J119 to K1529/J200 in the Luxman LV113/4/5 amps, also some Sony amps as well without changing anything else, and it all worked fine in every case. Also, I always make the same changes to both channels, AFTER I have ascertained that the one I make them to first, operates correctly. The higher Ciss is proportional to the higher Id, (which in turn actually makes it possible for the amp to drive more difficult loads), for normal operation this will not make much of a difference. Crss is also higher which slows down the output stage some. However, in the grand majority of cases, no-one designs amps with so little leeway that it would make a crucial difference.
Thanks very much ilimzn.
Just another quick question: I will try your method to test the mosfets:
http://www.diyaudio.com/forums/showthread.php?postid=1140902#post1140902
Can I perform the test without removing them from the board/circuit?
And if I am careful not to kill them with static, is there any way I may damage a good mosfet if I make a mistake while following your method with the multimeter. People say they are very delicate but I do not know how much.
Thanks and regards
Antonio
Just another quick question: I will try your method to test the mosfets:
http://www.diyaudio.com/forums/showthread.php?postid=1140902#post1140902
Can I perform the test without removing them from the board/circuit?
And if I am careful not to kill them with static, is there any way I may damage a good mosfet if I make a mistake while following your method with the multimeter. People say they are very delicate but I do not know how much.
Thanks and regards
Antonio
goodas said:My 20 year old Inca Tech Claymore has dropped a channel I suspect that the output MOSFETs have blown.
Does anybody know where I can get the following:
2 x 2sk414
2 x 2sj119
Thanks for any help.
This why I use IRFP240/9240, they are on ebay for less than £2 each. They certainly sound fine to me, I cant tell the difference between them and more expensive transistors. In fact I cant even hear cross over distortion before it is tuned out !!!
They are also cheap to replace should you do something silly and fry a set.
MOSFETS for Claymore
These are still readily available!
There is a company in London that deals with all Hitachi products, and sell what you want for abour £39, or you can cet them from HK/China.
www.hkinventory.com/ is one of the sources, or try www.utsource.com
Be sure to look for matched pairs - although I have found little difference with run-of-the-mill parts.
John
These are still readily available!
There is a company in London that deals with all Hitachi products, and sell what you want for abour £39, or you can cet them from HK/China.
www.hkinventory.com/ is one of the sources, or try www.utsource.com
Be sure to look for matched pairs - although I have found little difference with run-of-the-mill parts.
John
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