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Gyuri's Pass SONY VFET2 build.
Gyuri's Pass SONY VFET2 build.
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Old 12th September 2017, 05:57 PM   #111
Nelson Pass is offline Nelson Pass  United States
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Gyuri's Pass SONY VFET2 build.
It is a happy man with two multimeters.

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Old 12th September 2017, 05:59 PM   #112
Gyuri is offline Gyuri  Hungary
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Thanks, Papa,
You know, I have two other ones.
But I'm more happy with my two cats.
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Old 12th September 2017, 06:18 PM   #113
Gyuri is offline Gyuri  Hungary
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One of the channels I had a little problem.
On one of the channels I could not set the voltage symmetrically at T6-T7 and T8-T9.
The best what I can set was 0.9V against 2.0V.
Firstly, I suspected it is because that damned input JFETs, so I swapped them between channels.
Sockets are quite good, I think.
Error remained in its place.
So I began to measure impedances, compared good and bad channels.
It revealed quite quickly, one of the 47Ohm resistors for driver FETs were about 90Ohm.
It was a Caddock 915.
I have measured it before, so I was quite surprised.
As you know, I'm overjoyed everything.
Perhaps I have tightened more than enough the screw for poor Caddock.
Maybe it has some crack because of this, and it changed the value.
Never mind, I had another one.
But it costs to me about four bottle of beers.
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Old 12th September 2017, 07:14 PM   #114
brianco is offline brianco  Ireland
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Don't worry about the beer...the sound is more intoxicating!
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Old 12th September 2017, 08:11 PM   #115
Soundhappy is offline Soundhappy  France
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Any news about front-end mosfets individual heat sinks ?
Mouser P/N : 532-551002B00G
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Old 12th September 2017, 08:59 PM   #116
Gyuri is offline Gyuri  Hungary
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There is something really strange.
As I wrote above, I have changed 47Ohm resistor.
I've set up a test for approx. 1.5A current, as shown in the photo.
It worked like a charm about a hour or so, with cc. 5mV offset.
Then I wanted to set it as it should be.
There was a huge DC offset, and mismatch between test points T6-T7 and T8-T9, just as before!
That resistor, what I've changed, showed about 56Ohm, instead of its original 47Ohm value.
I really didn't hurt it, so I'm now really puzzled.
Only one reserve left.
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Old 13th September 2017, 12:13 PM   #117
Gyuri is offline Gyuri  Hungary
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Quote:
Originally Posted by Gyuri View Post
I really didn't hurt it, so I'm now really puzzled.
I say excessive self-confidence is not always good.
The whole mess above is certainly my fault.
Those two Caddocks went south by me.
(There are as many as eight bottles of beer. )
Most probably over tightened bolts, or perhaps I wasn't be careful enough when I bent those legs, or when I drilled M3 holes.
Second case was quite frightening, because it worked more than a hour.

Soundhappy, I don't use those little heatsinks.
All of the parts (2SK2013/2SJ313and Caddock MP915 47Ohm resistors) are thermally coupled with each other and main heatsinks.

It's been stable for over two hours now.
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Last edited by Gyuri; 13th September 2017 at 12:29 PM.
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Old 13th September 2017, 12:17 PM   #118
Gyuri is offline Gyuri  Hungary
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Forget to say, two TL431s were lost in the battle.
One more bottle of beer.
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Old 13th September 2017, 03:14 PM   #119
Gyuri is offline Gyuri  Hungary
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It sings for more than three hours now.
I'm a happy man, with two Sony VFET amp.
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Old 13th September 2017, 03:55 PM   #120
Dennis Hui is offline Dennis Hui  Canada
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Gyuri's Pass SONY VFET2 build.
Congratulations!
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