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#1 |
diyAudio Member
Join Date: Jul 2003
Location: Waterloo
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I'm building my first class A amp, the Zen IV, and am presently putting the power supply together. I want to look at the regulated power supply and see how much noise is actually there. I've got a Tek 2445 scope, however I can't deny I'm a little nervous about connecting it up to the power supply. I have no real basis for this fear, I just need someone to say, "Go ahead, hook up the scope, you won't fry it!" Thank you in advance for assuaging my irrational fears. On the off chance that my nervousness is valid, I'd appreciate knowing that too!
Cheers, Dave |
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#2 |
diyAudio Moderator Emeritus
Join Date: Jan 2003
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Hi Dave
Are you and your scope still alive? ![]() /Hugo ![]() |
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#3 |
diyAudio Member
Join Date: Apr 2003
Location: Brantford, ON
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check with your meter first LOL and make sure the supply is fused then go ahead with the scope
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#4 |
diyAudio Member
Join Date: May 2002
Location: Westende Resort, BE coast
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Check what with your meter first?
I don't understand these questions. What is the problem of putting a scope probe on a supply? The scope's only purpose in life is to do these things. Jan Didden |
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#5 |
diyAudio Member
Join Date: Jan 2004
Location: Bangkok, Thailand
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Hi Dave,
I know Oscilloscopes are fairly expensive, but they do have a very high input impedance. This simply means that they don't fry up easily. A lot of people hook them up to 220 Vac all the time in my lab, and they don't get fried. -Sean ![]() |
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#6 |
diyAudio Member
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take a look at the several application notes at Linear Technology on noise measurement. They are sprinkled through LLTC's literature -- App Note 70 comes to mind -- although it deals with switching regulators there is an appendix devoted to noise measurement.
to measure noise, you really have to measure it within a known bandwidth -- that's why some of the old TEK 5XXX series scope plugins (like the 5A22N differential amplifier) are so wonderful -- you can set them up for 10Hz to 10kHz bandwidth, and the scope was designed for measurements just like this in automotive and medical technology. The 5A22N measures down to 10uV/cm and as high as 50V/cm. There have also been designs in recent issues of AudioXpress for a low noise measurement preamplifer. |
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#7 |
diyAudio Moderator Emeritus
Join Date: Oct 2002
Location: Chicagoland
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FWIW, I routinely use my scope on tube equipment, with about 10 times higher voltages. To see what's going on with the power supply, just use the AC coupling for the input.
One other fun trick I've mentioned before is to connect a cap between the supply rail and a headphone amp. Play music or test tones through the amp and listen through headphones- you'll hear for yourself what's on the rail besides DC.
__________________
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is." |
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#8 | |
diyAudio Member
Join Date: Jul 2003
Location: Waterloo
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Quote:
Well, I'm fine. My scope, however, is not. I'm not exactly sure what happened, but when I connected it up there was a nice pop, and the scope now seems to be dead. So... that didn't turn out quite as I had hoped! Ahh well, I'm sure I'll get it back working soon enough. Dave |
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#9 | |
diyAudio Member
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Quote:
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#10 | |
diyAudio Member
Join Date: Jul 2003
Location: Waterloo
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Quote:
So how hard of a lesson is this? Do you know what's wrong with the scope, and how to fix it? Thanks for the information, btw. |
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