help with historical v-fets

[colwaiting]

I have heard about 1970's era V-fets,
such as the much loved Toshiba 2sk135/2sj 50
are these power j-fets, or somewhat conventional hexfets?
Reason for asking is that I have a few obsolete Sony 2sk60/2sj18, which are absolutely not available anymore, and they were identified as V-mos Jfets in google searches.
I'd like to test them and maybe use them somewhere. but the question of polarity has me stumped.
TIA--

[colwaiting]

OK- I guess the're lost in time!
Flat paks it'll be!

[Charles Hansen]

Hello -

Virtually all modern power FETs are vertical MOS types. The Hitachis you referred to are lateral MOS types that are better suited to audio in many ways. The numbers you mentioned are no longer made, but the equivalent plastic packages are, I believe 2SK1058 and the complement whose number I forget.

The Sony FETs you are looking for are not MOS types, but instead Junction types. There is absolutely no substitute for these parts. For more information on these and some similar Yamaha parts, look up an article in Audio magazine by Bascom King from around 1976 or 1977. You should be able to find this at a good university library.

Best regards,
Charles Hansen

[mrfeedback]

Hello Doug,
Exicon 10N10, 10P10, 10N20 and 10P20 are replacements for the Hitachi type fets - 2SJ50/2SK135 etc.
I use these in repairs of old high power mosfet amps, and they work fine.
As Charles says you may need to dig a little deeper to find info regarding the 2SK60/2SJ18 transistors.

Eric.

[Tomo]

Hello,

I hear they have a different name. It is Static Induction Transistor. It is sometimes refered to simply as SIT. Is it correct?

Does Exicon models operate similarly?

T

[mrfeedback]

Dunno.
I use the transistors in repairs, not simulations.

Eric.

[900gripen]

2SK60/2SJ18 are V-FETS used in some SONY amps of the mid-late 70's. Not to be confused with the markedly inferior Hitachi style
MOSFETS that appeared a little later. V-FETS perform like Triode valves/tubes whereas MOSFETs are akin to Pentodes in their characteristics and require much more feedback to acheive similar distortion figures. You can find these devices if you search the net, but be careful to match the Vp (pinch off) rankings. For example, the Sony TA-4650, 5650 and TAN-5550 can only use
rankings -54 t0 -57, whereas models such as the TA-8650 can use the full range -53 t0 -58. This is listed below the transistors type number. ie: A56. The P channel devices in paralell must match each other as must the N channel devices that are paralled, but the P and N channel devices can differ. The later Ta-N7 and TA-F7
V-FET amps have bipolars cascaded in the output stage so are more tollerant of a Vp mismatch. High distortion is the result of poor matching of the devices.

V-FETS are now rare and quite expensive to replace, so be careful.
But they do sound WONDERFUL!!

Static Induction Transistors are the modern equivalent of V-FETS, but are only available in milatary style devices. Some well-heeled audiophiles have experimented with them, with good results.

Yammaha and NEC also made this type of Power FET, but only Sony officially called them V-FETS.

[mrfeedback]

Quote from Meyer Sound site.

"MILO’s circuitry for the driver and output stages provides pure Class A operation. Four pairs of high-current, complementary V-FET transistors in each output channel provide 10 watts of pure Class A and 200 watts of Class A/B; the amplifier will only enter Class H operation during extremely loud musical passages. V-FETS are high-speed (72 ns Rise Time) and low on resistance compared to lateral FETS commonly used in audio amplifiers. "

Maybe they are using cheap modern ones ?.

Eric.