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Old 26th February 2011, 11:05 AM   #1
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Default b1 testing measuring new builds

greetings,

I've completed my B1 build which I ordered from Pass a couple of weeks ago.

firstly, let me say that this is a fantastic board and easy to build given the spacing fot the solder joints. highly reccommended.


My order shipped with the 2sk370 not the 170.

My first mistake was that I ommitted an initial measurement and soldered the sk's randomly. I hope that I don't have to unsolder because I used auricaps and its kind of tight in that area.

Is there a way of measuring the sk's in-circuit?
What other board measurements are required for acceptance?
Is there another thread which shows proper testing and measurement?

I've read somewhere but I can't remember where and for which product but some testers have fed devices with constant 1k sine wave using function generators. I don't mind purchasing one of these if it will help me with future projects. Any reccomendations here?






PS: I've only tested the power up and the led lights up.

If anyone can help, it would be appreciated.
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Old 26th February 2011, 11:23 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
you can check the Vgs of the amplifying jFET in each channel.
If the Idss of the Amp jFET is close to the Idss of the CCS jFET then Vgs is very close to zero mVdc.

Do not have speakers or amplifier connected when you probe around inside the B1 !!!!
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Old 26th February 2011, 11:37 AM   #3
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where do I check the Vgs ?

Is it on one of the legs of the jfet with DMM grounded?
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Old 26th February 2011, 11:43 AM   #4
AndrewT is offline AndrewT  Scotland
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Vgs is the Voltage between the Gate and the Source of the jFET
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Old 26th February 2011, 12:13 PM   #5
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one measures .003 the other .001
is this acceptable
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Old 26th February 2011, 02:36 PM   #6
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I guess this is acceptable.
Have to wait about 30seconds before stability at .001 and .003 Vgs values
feeding constant 18v and tried 20v with same result.

Going on to next test.
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Old 26th February 2011, 03:20 PM   #7
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The fets Pass Labs provides are matched sets, so I didnt think it mattered, perhaps I'm mistaken thinking it didnt matter, opps. Oh well, it sounds just great anyway.

Russellc
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Old 26th February 2011, 04:28 PM   #8
AndrewT is offline AndrewT  Scotland
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1mVdc and 3mVdc of Vgs indicates close Idss for the Jfets in the amp and CCS.

If this were a DC coupled B1 then the output offsets would be 1mV and 3mV. Both good results.
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Old 26th February 2011, 08:14 PM   #9
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Thanks,

that's great. I was either lucky in matching the pairs or the matched pairs I got from Pass were very closely matched as a quad.
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