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Building a symmetrical psu B1 buffer
Building a symmetrical psu B1 buffer
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Old 10th February 2012, 01:00 PM   #2421
KatieandDad is offline KatieandDad  United Kingdom
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Quote:
Originally Posted by wintermute View Post
I bought a batch of 100 from spencer and they ranged from about 6.5 t0 11. 2.2 is definitely very suspect.

Andrew, when did you start using 1R0? Isn't that a tad low? I used a 0.1% 100 ohm resistor and that seems to work quite nicely. Perhaps 100 ohms doesn't give quite enough resolution though for really close matching, a 10 ohm resistor would allow me to use the 200mV range on the multimeter rather than the 2V range... I assume this is the reason for going with such a low resistor value? Or is it because you can just use the reading without needing to divide by the resistance?

Tony.
I agree.

You do need at least 10R0 to get full resolution on most meters.

My initial measurements were taken with only the shunt of the meter as a load.
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Old 10th February 2012, 01:32 PM   #2422
KatieandDad is offline KatieandDad  United Kingdom
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Before I go tearing into my supplier.

I've just been looking at the datasheet for the 2SK170.

The parameters are quoted at Vds=10V Vgs=0V and Idss=3mA.

That's not too far from what I am seeing.
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Old 10th February 2012, 02:31 PM   #2423
KatieandDad is offline KatieandDad  United Kingdom
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Dalbani are being helpful. They are just as stunned as we are that they are being conned.
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Old 10th February 2012, 02:33 PM   #2424
KatieandDad is offline KatieandDad  United Kingdom
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My original SwapMeet post for 0-15 0-15 Toroidal has been amended. Apparently, these rescued transformers are 60VA and not 50VA as originally suspected.
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Old 10th February 2012, 02:34 PM   #2425
buzzforb is offline buzzforb  United States
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THere are different grades of fets. If you were sold BL fets, that is low. EVen if you were sld GR grade, I think that is still low.
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Old 10th February 2012, 02:39 PM   #2426
KatieandDad is offline KatieandDad  United Kingdom
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I've just been in contact with supplier. I think they are fakes.
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Old 10th February 2012, 02:45 PM   #2427
jean-paul is offline jean-paul  Netherlands
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For those that can use them: I just found a bag with a quantity of original 2SK170. I used them for finding matched pairs for 3 pieces DCB1 and they were left. make me an offer if you want them. Their Idss range from 7.XX to 10.xx mA.
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Old 10th February 2012, 03:58 PM   #2428
KatieandDad is offline KatieandDad  United Kingdom
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How many have you got.
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Old 10th February 2012, 06:00 PM   #2429
Salas is offline Salas  Greece
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Building a symmetrical psu B1 buffer
Quote:
Originally Posted by KatieandDad View Post
Before I go tearing into my supplier.

I've just been looking at the datasheet for the 2SK170.

The parameters are quoted at Vds=10V Vgs=0V and Idss=3mA.

That's not too far from what I am seeing.
That is about minimum transconductance expected. 22 milliSiemens is the low side GR(een) grade's bottom Yfs. Anything marked BL(ue) shall vary between 6-12mA IDSS @ 10V VDS with a midway Yfs of 37mS. Else its a bad or fake sample.
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Old 10th February 2012, 06:05 PM   #2430
Salas is offline Salas  Greece
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Building a symmetrical psu B1 buffer
Quote:
Originally Posted by KatieandDad View Post
Dalbani are being helpful. They are just as stunned as we are that they are being conned.
Check IDSS with this direct method again: http://www.diamondstar.de/transistor_matching_jfet.html
Show us a good macro picture of the JFETS there:
http://www.diyaudio.com/forums/parts...l-copy-44.html
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