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DIY Sony VFET Builders thread
DIY Sony VFET Builders thread
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Old 25th September 2021, 10:25 AM   #1951
MEPER is offline MEPER  Denmark
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Yes, and I can probably find a cheap heatsink 2nd hand.....and drill some holes.

Did they produce them in large batches and then depending on Vgs they where stamped KF, KE, JA etc? .....like JFET grades?

The JA-33 has a faint red "F" written on it......I wonder what that could mean......
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Old 25th September 2021, 10:28 AM   #1952
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DIY Sony VFET Builders thread
why bother?

it's just matter of gate voltage

get what you can
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Old 25th September 2021, 10:38 AM   #1953
MEPER is offline MEPER  Denmark
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The original VFETs are KF-33.
It was just that my "brain" likes to have similar in both channels and I have got one spare KF-33. But if I did not and only had the JA-33.
Would that be a "disaster" to have KF in one channel and JA in the other?
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Old 25th September 2021, 10:46 AM   #1954
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DIY Sony VFET Builders thread
as long you can set them to same Iq, you'll not hear difference

test them as shown
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Old 25th September 2021, 12:15 PM   #1955
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DIY Sony VFET Builders thread
Happened also to me a 2SJ28(KF) in shorted with the PEAK DCA75. With the circuit shown by ZM it was good.
The project is to build a negative Luminaria.
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Old 25th September 2021, 01:43 PM   #1956
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by MEPER View Post
This will require that I find a large heat sink for TO-3?
How would such a "test-schematic" look like for a P-channel?
Official schematic made by Mr. Pass
Have a good time
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Old 25th September 2021, 02:02 PM   #1957
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Ok, thank you!
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Old 25th September 2021, 02:27 PM   #1958
Soundhappy is offline Soundhappy  France
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@ MEPER

Give them nice 15 minutes of warm up time on the large heatsink.. then mesure Vgs
Edit : If possible use thermal TO-3 pads or mica with goop, transistor heat transfer condition are the same like in the real amplifier
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Old 25th September 2021, 02:47 PM   #1959
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I have some mica TO-3 isolators and also the white "grease".

A seller wants to sell 3 of these old boards......for not very much.
I only need one.....but forced to get all 3.

A lot of TO-3 holes......size of heatsink looks sufficient?
Should be possible to free heatsink from PCB and keep that and trash the "other stuff". Maybe a couple of the power resistors can be used also.

It look really old and "outdated".
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Old 25th September 2021, 02:50 PM   #1960
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Could put two heatsinks back to back for extra cooling......
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