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J49/K135 Fets.............Anybody have these?

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#2
The Hitachis in the early 80s were available in 3 voltage ranges.

2SK134/2SJ49 were in the same voltage range
2SK135/2SJ50 were in the same voltage range

The two devices you seek are not from the same voltage range. Tell us why you need these two and how they will be used.

I can help you with matched pairs of 2SK134/2SJ49.
 
#4
OK, thanks for the info. First, your specified K135, now you state K134.

I can help you with matched pairs of 2SK134/2SJ49. Are these what you want? If so, send me an email using the DIYaudio email messaging system.

I use a bona fide original Hafler MOSFET checker that can grade these MOSFETs into one of 7 categories (1-7). Do your MOSFETs in question have an add-on number either stenciled or hand written on them, a number 1-7? If either device is used in parallel pairs they must be matched on Vgs which my MOSFET checker can do.

Now, how do you know you need to replace the ones you have? These are very robust devices. In an amp other parts, such as on the PCB usually fail first, not the MOSFETs on the heat sinks.

Regardless, I will help if possible.
 

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#7
But, you have to realized that the original pairs were matched. Profusion in the UK will sell replacement devices but they are ungraded. In other words you might have to purchase10-20 each of them, measure their Vgs, and then put them into pairs based on ±VGS. This is why graded pairs are more expensive than single items and matched pairs are mostly unavailable.

You can replace Hitachis with Exicon (Profusion) devices if the MOSFETs are used in singles, such as in the Hafler DH-120 amp, but if they are used in pairs or triplets they must be matched.

Some amateurs claim that getting devices from the same date/batch number means they will match on Vgs but this apparently has shown not to be true. Or, you could insert a series resistor between the source and load -- to force each device to share current equally. But, I suppose that if this were done both channels would have to be wired in a similar fashion to keep the output the same at each channel.

Sorry to be so long-winded but users need to realize that just replacing a device is only part of what is needed. I use a bona fide original Hafler MOSFET checking meter to match pairs or triplets.
 

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#10
You can emulate the function of the Hafler tester with a couple of power supplies. It simply maps Vgs to Ids. One thing I have noticed is that it is difficult to mix'n'match original (Hitachi) parts with the replacement Exicon parts. It helps to have grab bag of assorted parts when trying to match a replacement with an incumbent in a parallel bank.
M
 
#11
slizm said:
I'm having trouble finding these parts and wondered if anyone can point me in the right direction. I need 2 of each(hitachi). Thanks in advance.
Click to expand...

Hi Slizm, I have 2 x 2SJ50 and 2 x 2SK135 for you all new/unused in antistatic bag. I payed 65 euro for them and they're yours for that same price.

I made quite a few class A amps with just 2 of these "complementary" types per channel and never matched them nor did I use any source-resistor ( warning: I did use gate stoppers, please no discussion on them again 😉 ). Never had any current, offset or other problems. When using dual or more parallel that is a different story of course. Wonderful components and very sturdy. I saw very few broken ones although they deteriorate with time in class A amps.

Capacity at the input differs ( I recall 600 pF vs. 900 pF ) so I used different value gate stopper on J50 and K135.
 
#16
pinkmouse Dick, can you still get those testers?
Click to expand...

The Hafler MOSFET checkers are no longer available. I recently saw one sell on eBay for $110 US! :bigeyes:

Here is an opportunity for some of you resourceful guys to put out a kit for a matching device. Not every reader understands how to match nor has the required power supplies.
 
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