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Old 8th April 2009, 02:11 AM   #81
EUVL is offline EUVL  Europe
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I etched a small PCB with 3 pads and wired them accordingly.

But you can do that esily also with a universal strip board. Just cut one of the strips to make 2 separate tracks for D & S, and use the neighbouring strip for gate.

Then hold the JFET down with a fine tweezer on the top of the SOT23 package in position on the PCB before applying voltage. Put a current limit on your power supply at say 30mA. I use 9V myself for matching.

As mentioned before, I shall make matched FETs available later when there is sufficient interest. The pioneers would have to suffer, as usual.




Patrick
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Old 14th May 2009, 04:51 AM   #82
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Just wanted to check in and report my boards finally arrived a few weeks ago. I have also ordered parts, and will be building and listening soon if all goes well.

Last weekend I built a BF862 matching rig. I cut two strips of adhesive backed copper and then soldered wires to the copper strips. I can post a picture if needed to "splain" better.

I hold the chips down with a plastic tool and count to 40 seconds with 10V applied. I am seeing parts well centered around 13ma Idss, with outliers at 12 and 14ma. Once measured, I tape the parts to copper foil with a part number and reading. These things are pretty hardy.

Bob
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Old 14th May 2009, 05:15 AM   #83
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Quote:
Originally posted by BFNY
Last weekend I built a BF862 matching rig. I cut two strips of adhesive backed copper and then soldered wires to the copper strips. I can post a picture if needed to "splain" better.
Please do... i have all the parts just waiting for my electronics guy to get back from a visit (unexpectedly extended) to his mom's

dave
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Old 14th May 2009, 03:01 PM   #84
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The US Post is rEEEEEally fast !!

I essentially did the same for matching, only with a custom etched PCB.

The Idss varies from batch to batch. The first 2 batches I had were all around 17mA +/- 2mA. The second batch varied between 12 and 16mA. So you are lucky in a way (or unlucky if your circuit would have required 16mA Idss).

At least there is some progress.

Meanwhile I have a dual version and a mixed version (1 DABF862 + 1 SOIC Opamp of any brand) in a single DIP8 footprint already finished on the drawing board. Just need some time to etch, solder and test. I now have all versions covered.




Patrick
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Old 15th May 2009, 04:15 AM   #85
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Here's the copper foil addition to my 2SK170 test fixture for testing IDss on BF862s
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File Type: gif bf862test_1 copy.gif (86.3 KB, 1379 views)
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Old 15th May 2009, 04:21 AM   #86
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The two center leads go to the HP 974A Multimeter, set for a 50 ma current range. This meter has 4.5 digits resolution, and was *not* an inexpensive model.

The two outer leads go to the + (red) and - (Black) leads of the 10V power supply. This HP supply is current limited 250 ma

This shows the BF862 in place and ready for testing.
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Old 15th May 2009, 04:24 AM   #87
BFNY is offline BFNY  United States
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This show the part being pressed in place to achieve the Idss reading

This is a typical value for the lot
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Old 31st May 2009, 04:42 AM   #88
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Gentlemen,

Any further progress ?


Patrick
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Old 31st May 2009, 05:27 AM   #89
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My electronics guy who is going to assemble & test has gotten stuck at his mom's... should be back soon.

This is at the top of his (growing) list.

dave
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Old 7th June 2009, 01:09 AM   #90
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Daniel came home for the weekend and put ours together. Here is a scan of the distortion plot. He'll drop in with comments.

He has to go back and finish fixing his mom's car, but when he gets back, we'll use these as buffers in a PLLXO for Tysen and have a listen.

dave
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