considering that input LTP Jfets are biased with CCS , each conducting smidge above 2mA , plenty of types are more than good enough
so , Toshiba singles 2SK246GR or 2SK246BL , 2SK170GR or 2SK170BL , duals 2SK389GR or 2SK389BL
adequate LSystems replacement types , same number , LSK instead of 2SK , A or B suffix instead of GR or BL
there are more adequate types , but I'm lazy to search for them , these are (always) from memory
so , Toshiba singles 2SK246GR or 2SK246BL , 2SK170GR or 2SK170BL , duals 2SK389GR or 2SK389BL
adequate LSystems replacement types , same number , LSK instead of 2SK , A or B suffix instead of GR or BL
there are more adequate types , but I'm lazy to search for them , these are (always) from memory
Yes, I know, Interfet dual fet is expensive. I also think every manufacturer has a selection of proprietary masks. It is meaningless to compare a simplified mask to a photograph. Moreover, the 2SK170 shows lower noise and Gm compared to the 2SK146, how do we know that Toshiba use the same process for both of them?
@Indra:
$20 or so for the IFN's is not too bad when you look at the NOF's (New Old Fakes) that go for $30-50 on eBay.
In a different thread, I've asked Scott Wurcer for the pic of the 2SK146, but he doesn't have any.
@Renehc:
Yes, the LSK389 is good because it looks and works the same as your 2N5566. A slightly better option would be the IFN5565 currently stocked at Mouser. Not cheap, but Mouser ships for free for orders > $50.
$20 or so for the IFN's is not too bad when you look at the NOF's (New Old Fakes) that go for $30-50 on eBay.
In a different thread, I've asked Scott Wurcer for the pic of the 2SK146, but he doesn't have any.
@Renehc:
Yes, the LSK389 is good because it looks and works the same as your 2N5566. A slightly better option would be the IFN5565 currently stocked at Mouser. Not cheap, but Mouser ships for free for orders > $50.
I have been thinking on this issue, the metal can TO71 package used for the IFN is usually regarded as technically superior compared to a plastic TO92. I guess we never know how the part compared sonically unless we do an AB listening test.
Zung
you did everything in this thread , except helping OP
you see that his knowledge of subject is lacking , that being main reason he asked ......
and you're just confusing him with deeper analysis , completely over his head
Renehc , read what I wrote in post #42 , and that's practically all you need to know regarding JFets in your preamp if they need to be changed at all
same applies to bipolar transistors - BC550/560 or ZTX450/550 are perfect there , if they need to be changed at all
besides that - change electrolytic caps and that's it
of course , taking care of possible difference in parts pinout is a must
you did everything in this thread , except helping OP
you see that his knowledge of subject is lacking , that being main reason he asked ......
and you're just confusing him with deeper analysis , completely over his head
Renehc , read what I wrote in post #42 , and that's practically all you need to know regarding JFets in your preamp if they need to be changed at all
same applies to bipolar transistors - BC550/560 or ZTX450/550 are perfect there , if they need to be changed at all
besides that - change electrolytic caps and that's it
of course , taking care of possible difference in parts pinout is a must
OK, OK, here's the concise shopping list:
Fets: IFN5565, Mouser part number 106-IFN5565, 2 pcs.
Electrolytics: Elna Silmic 470uF 50V, Mouser part number 555-RFS50V471MJ8#5, 4 pcs.
The above should meet Mouser's free ship criterium.
Other transistors: I don't like the ZTX's, BC550 are OK, should be in one of the tech's drawers
Fets: IFN5565, Mouser part number 106-IFN5565, 2 pcs.
Electrolytics: Elna Silmic 470uF 50V, Mouser part number 555-RFS50V471MJ8#5, 4 pcs.
The above should meet Mouser's free ship criterium.
Other transistors: I don't like the ZTX's, BC550 are OK, should be in one of the tech's drawers
Completely over my head.... BUT, I really like your enthusiasm (why we are here I believe), going thru different options, trying to help me out - thank you ALL for this!
Will show post #42 to the tech.
Zung wrote exactly what to use, great - will pass that on to the Tech also.
I think that.. if LSK389 will do a good job, and its cheaper, that will be fine.
The tech said that around 7 transistors where to be changed.
Regards.
Thank you Zung
Will use the LSK389, instead of the IFN5564, because of the price.
Oooh I like that, a lot easier for me now
Will pass it on to the tech.
I might return when I get the PRE back in the chain, and have had some listening.
I have had the pleasure of owning a FET Nine in the past - and honestly I'm quite surprised that 7 transistors should need replacing. If I understood you correctly it actually does play except that it has intermittent noise and some hissing?
Wouldn't expect the relay then either.
To me this hints more at the degrading parts of the circuit which is the power supply electrolytics starting to fail, which could cause the symptoms mentioned. I replaced the main caps (Sprague) in mine for good measure - while degraded, they were still functional.
Part from that I can only back up the inputs from ZEN
But then again if the the tech did measure the components properly for failure....
Puzzled towards what would have caused that as it's otherwise build to last - lightning perhaps.
The output caps to me had an easily recognizeable signature - not bad, but I immediately knew what I was listening to even before having the lid off
Wish you luck with the repair!
Wouldn't expect the relay then either.
To me this hints more at the degrading parts of the circuit which is the power supply electrolytics starting to fail, which could cause the symptoms mentioned. I replaced the main caps (Sprague) in mine for good measure - while degraded, they were still functional.
Part from that I can only back up the inputs from ZEN
But then again if the the tech did measure the components properly for failure....
Puzzled towards what would have caused that as it's otherwise build to last - lightning perhaps.
The output caps to me had an easily recognizeable signature - not bad, but I immediately knew what I was listening to even before having the lid off
Wish you luck with the repair!
I have had the pleasure of owning a FET Nine in the past - and honestly I'm quite surprised that 7 transistors should need replacing. If I understood you correctly it actually does play except that it has intermittent noise and some hissing?
Wouldn't expect the relay then either.
To me this hints more at the degrading parts of the circuit which is the power supply electrolytics starting to fail, which could cause the symptoms mentioned. I replaced the main caps (Sprague) in mine for good measure - while degraded, they were still functional.
Part from that I can only back up the inputs from ZEN
But then again if the the tech did measure the components properly for failure....
Puzzled towards what would have caused that as it's otherwise build to last - lightning perhaps.
The output caps to me had an easily recognizeable signature - not bad, but I immediately knew what I was listening to even before having the lid off
Wish you luck with the repair!
Hello Norgaard.
It plays yes.
Background noise all the time, not loud.
And then this hissing, and “pop”-noises sporadically.
Im beginning to think about taking it to another tech anyway, and have not heard from him since tuesday. (Which I should have).
Thank you for the input
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