Hi Guys,
I just received a sampling of LU1014Ds (my first ones) and I can't believe these are the real deal, I mean, how can something this small have a Pdiss of 69W? These are only slightly bigger than a TO-92. Are they really this small?
Too funny.
Thanks all.
I just received a sampling of LU1014Ds (my first ones) and I can't believe these are the real deal, I mean, how can something this small have a Pdiss of 69W? These are only slightly bigger than a TO-92. Are they really this small?
Too funny.
Thanks all.
Yes, they are really that small. Like in other parts of life, utter satisfaction can depend as much on the implementation as on the size 😎
From the ZV8 article (https://firstwatt.com/pdf/art_zv8.pdf):
"Even though it’s rated at 69 watts, realistically I’d be afraid to
operate the package at more than about 10 watts or so. A TO-251 is a small
device, and you have to work to get the heat away from it."
"Even though it’s rated at 69 watts, realistically I’d be afraid to
operate the package at more than about 10 watts or so. A TO-251 is a small
device, and you have to work to get the heat away from it."
Thanks guys,
Now I am trying to determine if these are real without destroying them, can we test Vgs and Idss without a heatsink? If so, how? I have tried the small signal FET matching technique but that doesn't seem to work on these, unless I need big current to get them going. Or unless they are fake?
Cheers
PS I just found this thread from 2006 describing a way to test these....going to try it now...
Matching LU1014D
Now I am trying to determine if these are real without destroying them, can we test Vgs and Idss without a heatsink? If so, how? I have tried the small signal FET matching technique but that doesn't seem to work on these, unless I need big current to get them going. Or unless they are fake?
Cheers
PS I just found this thread from 2006 describing a way to test these....going to try it now...
Matching LU1014D
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The best way to find out if they're real is to build an SIT tracer device. Google "FrankenTracer" and you'll find an excellent tutorial on how to build one and use it. I built one to test my SMD LU1014D devices. It was a fun project. Teaches you how SITs work as an added bonus.
Link:
Link:
Yes, this was already on my radar, very simple and cool...I just haven't made the time to build it yet. Trying to do it with just a DMM for now.
Thanks!
Why bother doing this, as I told you, I’ll send you my extra matched pair which are already soldered to a nice pcb to help dissipate the heat away from the poor little guy 😂
You can also build the tester and have fun.
You can also build the tester and have fun.
Exactly! Trying to learn some new tricks and add to my test jigs. 😀
I just ran thru the 10 I received with Nelson's simple cct as above, without heat sink, and I have 4 with Vgs 1.05, 4 @ .923 and 2 @ .765. Cool. So far they seem real. I can see the Vgs climb as they heat, I just took the initial reading after 2 seconds. I will build the curve tracer tomorrow and learn some more. I have been snowed out at work for a few days so I am taking advantage of my "time off".
Thanks Eric!
Cheers
I still have a bunch of those LU fets floating around. I contemplated soldering them down to a copper heat spreader using In/Sn solder, which has a lower melting point than the average Pb/Sn alloy.
Nota bene, when you mount these up in circuit, be sure to heat sink them very well. Even if you think they're only dissipating 4-5W, that amount of heat will destroy them if it isn't sinked away properly. Trust me, I've destroyed a couple this way.
https://www.diyaudio.com/community/threads/lovoltech-lu1014-power-jfet-group-buy.371283/post-6627824
Normal Pb/Sn, preheat both parts to 120°C in an oven.
No problem with a large soldering tip with enough heat capacity.
https://www.weller-tools.com/profes...s/WE+Line/Mains-powered+soldering+irons/W+201
Patrick
Normal Pb/Sn, preheat both parts to 120°C in an oven.
No problem with a large soldering tip with enough heat capacity.
https://www.weller-tools.com/profes...s/WE+Line/Mains-powered+soldering+irons/W+201
Patrick
I like the heat spreader idea...and something like this should solder it just fine. Weller SP-175, I've had it for years to solder big coax cable connectors.
I also picked up a 300W lamp tonight for Frankentracer, I think I have everything else here to build it.
Pictured among the LU1014s.
cheers
I replaced that big tip with a smaller one.
The trick is first to pre-tin the back of the LU1014 and the spreader.
Place them together and just melt the pre-tin with the solder.
Done in less than 5s.
Patrick
The trick is first to pre-tin the back of the LU1014 and the spreader.
Place them together and just melt the pre-tin with the solder.
Done in less than 5s.
Patrick
Okay, I built the Frankentracer on a breadboard just to get it going and make a few quick tests, and I am seeing a trace on the scope but it's backwards to what it should be. I've double checked all connections and diode directions, I can change the current flow and display by turning the bias control and see the Vgs change, the device gets warm...I've only had 2 cups of coffee, maybe need more. 😎 As this is my first exposure to curve tracing and power JFETs, and the possibility these are fake....I'm not sure what this indicates.
What am I doing wrong?
Thanks!
Thanks! I tried that and it just turns the "hockey stick" upside down, so it's pointing down instead of up. The device starts conducting as soon as I raise the variac from zero, draws .45A and gets warm, the 1R and 300W bulb also get warm, and when I move the Vgs back and forth the current stays at .45A.
Something is still not quite right....
The LU has ridiculously high gain. It will oscillate without trying very hard. Vds over 6v and it becomes unstable. This is my experience from curve tracing hundreds of SITs including the a large pile of LU.