Last edited:
How do you match? I have 8, but afraid to ruin them by my matching activities
I am using the locky_z curve tracer, which was discussed here on diyaudio.
Nelson Pass suggested to test them at 500mA and 1A Ids, match for Vgs:
You need probably a bench power supply with two adjustable voltages for Vgs and Vds.
-Heatsink the transistor
- Apply Vgs first, before applying Vds (IMPORTANT !)
- Then apply voltage between Drain and Source
I think for 2sk82 it is safe to start with Vgs of -20Volt and then slowly increase, while you watch Ids.
For 2sj28 you would start at Vgs of +20Volt and slowly decrease while watching Ids.
Re-check polarities I mentioned, as I am not 100% sure about + and - here.
As you probably now:
The depletion mode transistors will self-destruct quickly if you do not apply Vgs before Vds, as they will conduct a lot of current.
To safe-guard the fets and prevent possible sudden-death one option is to:
- Do initial tests with a resistor (large light bulb) between cable and drain, such that Ids will be limited to max. approx. 900mA. Test the light bulp with your power supply to determine max. current.
- When initial tests work and you have save Vgs values resulting in low Ids, you could do the actual measurements without the light bulb.
A second option is to start with low Vds, and sloowly increase it:
You could do first tests with given Vgs, but low Vds. If you start from 0 Volt Vds, there would be a sharp and quick increase in Ids when you get higher than Vp (pinch-off voltage), so careful when starting from 0Volt Vds - increase veeeery slowly.
As I am not so sure how quickly Id goes up, when Vds get's higher than Vpinch-off, I'd probably go for the lightbulb approach....
Last edited:
Yeah, I visit the First Watt site twice a day
I wrote a standard apology for my inattention to the site:
My apologies. I have been unbelievably busy the past few months
with moving two companies and my residence, remodeling a guest house,
getting the X.8 amplifiers finished and launched, building First Watt
production, designing Sony SIT amplifiers designing four new First Watt
power amplifiers, 2 DIY Sony SIT amplifiers, Yamaha SIT amplifier, new slot
loaded OB speaker for Lowthers, and redesigning the B4 crossover network
and the B1, B2 and B3 pieces.
designing four new First Watt
power amplifiers
Mr Pass can we please have some preliminary informations about specifics and devices used in new upcoming First Watt amps.
Many thanks
Best regards
I wrote a standard apology for my inattention to the site:
My apologies. I have been unbelievably busy the past few months
with moving two companies and my residence, remodeling a guest house,
getting the X.8 amplifiers finished and launched, building First Watt
production, designing Sony SIT amplifiers designing four new First Watt
power amplifiers, 2 DIY Sony SIT amplifiers, Yamaha SIT amplifier, new slot
loaded OB speaker for Lowthers, and redesigning the B4 crossover network
and the B1, B2 and B3 pieces.
I'll write my all further time apology , right away :
My apologies. I have been unbelievably busy , waiting for new Mana from Pa ,
which is unbelievably busy the past few months with
moving two companies and his residence, remodeling a guest house,
getting the X.8 amplifiers finished and launched, building First Watt
production, designing Sony SIT amplifiers designing four new First Watt
power amplifiers, 2 DIY Sony SIT amplifiers, Yamaha SIT amplifier, new slot
loaded OB speaker for Lowthers, and redesigning the B4 crossover network
and the B1, B2 and B3 pieces.
If you intend to match the VFETs - below curves give you an idea, where Vgs might be.
Vds=20 V, Ids=500mA, Vgs value (average) in measured group:
2sk82: -8.8V (avg), (range: -9.8 to -7.0)
2sj28: 9.6V (avg), (range: 12.4 to 7.3)
Vds=10V, Ids=500mA:
2sk82: -6.9V (avg), (range: -7.7 to -5.4)
2sj28: -8.0V (avg), (range: -10.4 to -6.0)
Attached graph shows measurements at 10V Vds.
2sk82 curves sit together nicely (all KE-33) - sony factory matched and ranked.
The 2sj28 however (also KE-33) spread out about 5Volt Vgs.
I wonder whether that is 'aging', chemical deterioration of the 2sj28's or more loose factory matching requirements for the 2sj28's ??
In the graph:
red: 2sk82 KE-33
blue: 2sj28 KE-33
yellow: 2sk60 KS-55
green: 2sj18 - KZ-55
Vds=20 V, Ids=500mA, Vgs value (average) in measured group:
2sk82: -8.8V (avg), (range: -9.8 to -7.0)
2sj28: 9.6V (avg), (range: 12.4 to 7.3)
Vds=10V, Ids=500mA:
2sk82: -6.9V (avg), (range: -7.7 to -5.4)
2sj28: -8.0V (avg), (range: -10.4 to -6.0)
Attached graph shows measurements at 10V Vds.
2sk82 curves sit together nicely (all KE-33) - sony factory matched and ranked.
The 2sj28 however (also KE-33) spread out about 5Volt Vgs.
I wonder whether that is 'aging', chemical deterioration of the 2sj28's or more loose factory matching requirements for the 2sj28's ??
In the graph:
red: 2sk82 KE-33
blue: 2sj28 KE-33
yellow: 2sk60 KS-55
green: 2sj18 - KZ-55
I wrote a standard apology for my inattention to the site:
My apologies. I have been unbelievably busy the past few months
with moving two companies and my residence, remodeling a guest house,
getting the X.8 amplifiers finished and launched, building First Watt
production, designing Sony SIT amplifiers designing four new First Watt
power amplifiers, 2 DIY Sony SIT amplifiers, Yamaha SIT amplifier, new slot
loaded OB speaker for Lowthers, and redesigning the B4 crossover network
and the B1, B2 and B3 pieces.
Respect Mr. Pass! That's busy indeed.
Especially moving your residence and companies are the most dramatic events in life....
Walter
Mr Pass citation from First Watt news page :
" Watt's New?
3/14/2014:
Where does the time go? I have received enough concerned messages that I had to work up a standard response:
My apologies. I have been unbelievably busy the past few months with moving two companies and my residence, remodeling a guest house, getting the X.8 amplifiers finished and launched, building First Watt production, designing the Sony SIT amplifier, designing four new First Watt power amplifiers, two DIY Sony SIT amplifiers, two Yamaha SIT amplifiers, another slot loaded OB speakers for Lowthers, and redesigning the B4 crossover network, B2 and B3 pieces. And these are just things I can tell you about.
I guess I'm trying to get everything done before I get old.... Anyway, everything's great and I'll have a bunch of goodies for you shortly."
http://www.firstwatt.com/wattsnew.html
Thanks Mr Pass !
" Watt's New?
3/14/2014:
Where does the time go? I have received enough concerned messages that I had to work up a standard response:
My apologies. I have been unbelievably busy the past few months with moving two companies and my residence, remodeling a guest house, getting the X.8 amplifiers finished and launched, building First Watt production, designing the Sony SIT amplifier, designing four new First Watt power amplifiers, two DIY Sony SIT amplifiers, two Yamaha SIT amplifiers, another slot loaded OB speakers for Lowthers, and redesigning the B4 crossover network, B2 and B3 pieces. And these are just things I can tell you about.
I guess I'm trying to get everything done before I get old.... Anyway, everything's great and I'll have a bunch of goodies for you shortly."
http://www.firstwatt.com/wattsnew.html
Thanks Mr Pass !
Last edited:
Received !
Interesting explanation
thanks R-K for your share
All in a day's work....
I doubt these old papers are worth much, but nice to have just for the record.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.