vfet from hitachi 2SK77,2SK76,2SJ26???

[Tomek.W.]

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?

[jacco vermeulen]

Fakes

[Tomek.W.]

Originally Posted by jacco vermeulen

Fakes

I just wonder what for hitachi who is one of the most semiconductor producer would like to fake a transistors???

[jacco vermeulen]

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)

[mos57]

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

[jacco vermeulen]

Originally Posted by mos57

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

Originally Posted by mos57

2SK77 must be much larger

Half an inch longer than regular TO3s

[Tomek.W.]

Originally Posted by mos57

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

[Tomek.W.]

Originally Posted by Tomek.W.

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

[mos57]

Originally Posted by Tomek.W.

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).

[tiefbassuebertr]

ckeck out also this thread:
Oversized TO-3 TO3 like Yamaha 2SK77 and NEC 2D363 - Overview