vfet from hitachi 2SK77,2SK76,2SJ26??? - diyAudio
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Old 30th December 2009, 10:11 PM   #1
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Default vfet from hitachi 2SK77,2SK76,2SJ26???

I have those at home
what do you think about them. Are the vfet or other transistors. The nr saying that this should be a vfet normaly made by yamaha, but those are made by hitachi.
How can I check do those are vfet, is there any way to check it without the datasheet?
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Old 30th December 2009, 10:20 PM   #2
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Fakes
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Old 30th December 2009, 10:26 PM   #3
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Quote:
Originally Posted by jacco vermeulen View Post
Fakes
I just wonder what for hitachi who is one of the most semiconductor producer would like to fake a transistors???
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Old 31st December 2009, 10:46 AM   #4
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That's assuming Hitachi manufactured them.

Yamaha and NEC got into VFETs right after Sony started producing amps with the J18/K60.
Hitachi developed their Lateral MOSFETs series as an alternative, which was less costly in manufacturing.
Main reason why yours are not genuine.

Secondly : J26/K76/K77 are Yamaha numbers, no 2 Japanese semi-brands manufacturer identical labelled devices.
Thirdly : the uni-style printing on your devices, highly uncommon for the era of devices without manufacturer logo.
(Forth : the 5H-6H-7H code lots look like a million dollar sweepstake ticket)
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Old 31st December 2009, 11:39 AM   #5
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It seems fake. 2SK77 must be much larger than 2sk76/2sj26. The package was a mammuth TO-3

Also Hitachi have made Vfets (2sk89-2sj29) if i remember.

However by this first simple mode you can check it.
With a multimeter on diode (for N devices 2sk76-77) put positive terminal on gate and negative on source or drain: you must measure a pn junction
(0,4-0,5V).
Then across Drain to Source you must measure a resistance of about 0,5-1,5 Ohm.
That is similarly to measure a signal jfets.

Francesco
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Old 31st December 2009, 12:02 PM   #6
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Quote:
Originally Posted by mos57 View Post
Hitachi have made Vfets 2sk89-2sj29
Indeed, and used in amps of Hitachi's subsidiary company Lo-D.
But that was mid-70s, a couple of years before the first Lateral MOSFETs came out, with Lo-D label.

The J29/K89 are a good example of how different the Hitachi print looks

Quote:
Originally Posted by mos57 View Post
2SK77 must be much larger
Half an inch longer than regular TO3s
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Last edited by jacco vermeulen; 31st December 2009 at 12:27 PM.
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Old 31st December 2009, 01:06 PM   #7
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Quote:
Originally Posted by mos57 View Post
It seems fake. 2SK77 must be much larger than 2sk76/2sj26. The package was a mammuth TO-3

Also Hitachi have made Vfets (2sk89-2sj29) if i remember.

However by this first simple mode you can check it.
With a multimeter on diode (for N devices 2sk76-77) put positive terminal on gate and negative on source or drain: you must measure a pn junction
(0,4-0,5V).
Then across Drain to Source you must measure a resistance of about 0,5-1,5 Ohm.
That is similarly to measure a signal jfets.

Francesco
With a multimeter on diode is 0,42v
Then across Drain to Source you must measure a resistance of about 2 Ohm
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Old 31st December 2009, 02:21 PM   #8
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Quote:
Originally Posted by Tomek.W. View Post
With a multimeter on diode is 0,42v
Then across Drain to Source you must measure a resistance of about 2 Ohm
on diode is 0,42v
across Drain to Source 2 ohm

sorry for grama errors
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Old 31st December 2009, 04:51 PM   #9
mos57 is offline mos57  Italy
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Quote:
Originally Posted by Tomek.W. View Post
on diode is 0,42v
across Drain to Source 2 ohm

sorry for grama errors
Very well. we are in the right direction.

You must measure the 0,4V pn voltage either among gate to source and among gate to drain.
About 2 ohm Resistance you must measure between D-S in either directions.

If these are in that way, pheraps they are good. (sure they not are mosfet)

To verify these devices in deep you need a circuit with: (Example is for N devices)

1 power supply of about 25-35 Vdc
1 10k Ohm 5-10 W resistor wired from Drain to positive rail
1 1k Ohm 5 W variable resistor wired from source to negative rail.
1 piece of wire from negative rail to gate.

It is better if you put device on a heatsink

Start with variable resistor to max value.
Put a voltmeter at the two ends of 10k resistor.
You would read a voltage drop on resistor.
If no, then you must diminuish slowly the value of variale resistor on the source.
Generally, the N Vfets are going in on state when the Vgs is lower than -15V but is depend on model and rank (-5V at least).

Last edited by mos57; 31st December 2009 at 04:59 PM.
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Old 9th June 2010, 11:29 AM   #10
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ckeck out also this thread:
Oversized TO-3 TO3 like Yamaha 2SK77 and NEC 2D363 - Overview
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