Good things grow slowly (ALPHA 20)
Today I got my hFE tester so I started probing my 24 pieces of KSA992FBU for two pairs to complete (still need to drill/tap the heatsinks, so no where near to completion in a long time) my ALPHA20.
Now this is the first time I did measure the hFE of Transistors, and have a question.
There where 3 transistors that did not measure stable on my test rig, so only 21 measurements.
This is the list of measurements
* means stable from first measurement.
There are plenty of transistors that match on a hFE of 395 (nine in total(these are the "bold ones")), but these vary in the "Uf (mV)" measurements, how important is this Uf value in the selection process?
Today I got my hFE tester so I started probing my 24 pieces of KSA992FBU for two pairs to complete (still need to drill/tap the heatsinks, so no where near to completion in a long time) my ALPHA20.
Now this is the first time I did measure the hFE of Transistors, and have a question.
There where 3 transistors that did not measure stable on my test rig, so only 21 measurements.
This is the list of measurements
Code:
part hFE Uf (mV)
01 [B]395 646[/B]
02 484 637
03 [B]395 647[/B]
04 402 642
05 [B]395 642 *[/B]
06 [B]395 643 *[/B]
07 382 644
08 435 640
09 [B]395 643[/B]
10 [B]395 646[/B]
11 [B]395 642[/B]
12 [B]395 641[/B]
13 384 641
14 411 637
15 387 637
16 407 638
17 [B]395 642[/B]
18 380 647
19 379 647
20 382 643
21 411 642
22
23
24There are plenty of transistors that match on a hFE of 395 (nine in total(these are the "bold ones")), but these vary in the "Uf (mV)" measurements, how important is this Uf value in the selection process?
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Don't worry about matching the forward voltage drop, it's all based on voltage drop of intrinsic silicon diode drop in transistor. The Hfe's you have are the ones to match and you have plenty of 395's to go with. The other variable will be the voltage drop across your MOSFETs under load, it will add some variability. I typically get 0mV to under 10mV DC offset matching just Hfe, and this is more than fine. Excellent considering there is not a single adjustment to make and there are no closed loop opamp servos in the circuit.
First mono looks somewhat like this. I don't know, side looks kinda heavy, large flat surface. It's was black at first, but it looked like way heavier. Maybe I should paint it partially black? 6mm tinted glass at the top. Once again, skeleton case was much cooler looking.
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Would you like to use something like these over the fans?
1 pcs DC Fan Grill Protector Metal Finger Guard 120mm 12cm Silver Tone for PC | eBay
1 pcs DC Fan Grill Protector Metal Finger Guard 120mm 12cm Silver Tone for PC | eBay
Thanks guys, I'm quite sure that this kinda build will be something to like or hate.
Gaborbela, I have tried couple of things already but everything seems to increase noise level. Even that alu plate increased fan noise, it might be a little too small hole. But I will think of something there.
Gaborbela, I have tried couple of things already but everything seems to increase noise level. Even that alu plate increased fan noise, it might be a little too small hole. But I will think of something there.
There are some finishin still to do: change all bolts, cover for vent, cover for fans, feets, maybe some painting and sonething for the sides etc. Heatsink temps rised to 56c with casing on but I think it's ok. L-clamps are still way cooler. Okay, first one is about ready now 
time to keep a little vacation and then another one. Maybe it needs that big vu-meter also.
time to keep a little vacation and then another one. Maybe it needs that big vu-meter also.Attachments
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