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front_range
Joined: 03 Mar 2008
Posts: 64
Location: North of Colorado Springs
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| Posted: Thu Oct 23, 2008 5:34 pm Post subject: High Voltage Measurements |
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I've got a Barco 708 I built from parts, so I want to do a complete setup before I hang it from the ceiling. I'm really nervous around high voltage. I seem to recall you should not use a bench DMM to do this, is that right? I have a Fluke 80K-40 HV probe with an AC powered Fluke 8050A bench DMM, but I don't have a battery powered DMM. I wanted to make sure I need one before I go buy one. Any other safety tips?
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Oct 24, 2008 1:54 am Post subject: Re: High Voltage Measurements |
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| front_range wrote: | | I've got a Barco 708 I built from parts, so I want to do a complete setup before I hang it from the ceiling. I'm really nervous around high voltage. I seem to recall you should not use a bench DMM to do this, is that right? I have a Fluke 80K-40 HV probe with an AC powered Fluke 8050A bench DMM, but I don't have a battery powered DMM. I wanted to make sure I need one before I go buy one. Any other safety tips? |
Don't stand in the full bathtub while probing this. 
Seriously though. Keep one hand in your pocket. DO NOT rest your free hand on the projector chassis. If you get zaped in that postion the voltage could run across your heart.
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front_range
Joined: 03 Mar 2008
Posts: 64
Location: North of Colorado Springs
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| Posted: Fri Oct 24, 2008 11:32 am Post subject: |
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I was looking more for practical advice on how to make the measurement on the 30KV circuit. My HV probe is too fat to reach inside the splitter connector where they tell you to take the measurement. Can you just hang a wire off the tip to reach inside the splitter without getting arc-over, or will taking an indirect measurement off the divider on top of the splitter be accurate enough?
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Fri Oct 24, 2008 1:08 pm Post subject: |
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Your 8050A will be just fine, that's a great meter I have one myself, whoops actually I think mine is a 8060A but they are similiar.
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Walter
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Chuchuf
Joined: 11 Mar 2006
Posts: 548
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| Posted: Fri Oct 24, 2008 2:24 pm Post subject: |
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| front_range wrote: | | I was looking more for practical advice on how to make the measurement on the 30KV circuit. My HV probe is too fat to reach inside the splitter connector where they tell you to take the measurement. Can you just hang a wire off the tip to reach inside the splitter without getting arc-over, or will taking an indirect measurement off the divider on top of the splitter be accurate enough? |
Depending on the depth of the splitter hole what I have done is to take a spring from a ball point pen and put it on the tip of the probe so that it will extend to the bottom of the splitter.
Terry
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front_range
Joined: 03 Mar 2008
Posts: 64
Location: North of Colorado Springs
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| Posted: Fri Oct 24, 2008 2:27 pm Post subject: |
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So you've done this with the Barco splitter and you didn't have a problem with internal arc-over?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Fri Oct 24, 2008 2:54 pm Post subject: |
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I would not bother with the checking of the HV section. Barco HV sections either work or don't work, they do not need periodic calibration.
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front_range
Joined: 03 Mar 2008
Posts: 64
Location: North of Colorado Springs
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| Posted: Fri Oct 24, 2008 2:57 pm Post subject: |
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Ok, that's better yet. Thanks Curt. I assume I can skip focus voltage adjustment too?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Fri Oct 24, 2008 4:35 pm Post subject: |
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Yes. If the tubes or focus block drift out of range, you can tweak that trimpot, but if the side controls bring the focus into range at some point in their travel, you're fine.
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front_range
Joined: 03 Mar 2008
Posts: 64
Location: North of Colorado Springs
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| Posted: Fri Oct 24, 2008 4:36 pm Post subject: |
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That makes perfect sense. Thanks again!
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