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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Bad probe-what's wrong?
I got my new to me BK precision 4001A function generator and I
thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric |
#2
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Bad probe-what's wrong?
On Thursday, January 24, 2019 at 2:23:49 PM UTC-5, wrote:
I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Do you mean you're seeing more of a triangle wave with 1/5 div peak to peak? |
#3
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Bad probe-what's wrong?
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#4
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Bad probe-what's wrong?
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#7
Posted to sci.electronics.repair
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Bad probe-what's wrong?
On Thursday, January 24, 2019 at 1:23:49 PM UTC-6, wrote:
I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Sounds like it's AC coupled. |
#8
Posted to sci.electronics.repair
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Bad probe-what's wrong?
On Thursday, January 24, 2019 at 2:23:49 PM UTC-5, wrote:
I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Hmm well I'm not much of a probe guy, but your probe has to be compensated for the input impedance (R and C) of the 'scope. It could be that the probe is not designed to work with the input of your scope. Is it a x10 probe? George H. |
#9
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Bad probe-what's wrong?
On Thursday, January 24, 2019 at 5:28:49 PM UTC-5, wrote:
On Thu, 24 Jan 2019 13:38:54 -0800, Paul Drahn wrote: On 1/24/2019 1:27 PM, wrote: On Thursday, January 24, 2019 at 2:23:49 PM UTC-5, wrote: I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Do you mean you're seeing more of a triangle wave with 1/5 div peak to peak? Perhaps the prob has been repaired and the wrong coax used. Probably should be 95-100 ohm. Paul I bought the probe new many years ago and have never seen any reason to repair it. There is no obvious damage. Could dropping it have caused the problem? Eric Oh, it worked in the past? Or maybe you've never had a good square wave to check it with? GH |
#10
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Bad probe-what's wrong?
On Thursday, 24 January 2019 22:27:13 UTC, wrote:
On Thu, 24 Jan 2019 13:27:38 -0800 (PST), wrote: On Thursday, January 24, 2019 at 2:23:49 PM UTC-5, wrote: I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Do you mean you're seeing more of a triangle wave with 1/5 div peak to peak? What I mean is that if the wave was a proper shape there would be two horizontal lines 1.5 divisions apart. These lines have a shape that is a curve that starts fairly steep and then gets closer to flat. At the point where the curves are closest to flat I would expect to see 1.5 divisions separation. but it's more like 1/5 of a division. Eric So if I guess correctly the probe is suffering poor hf response. Without any info from you on your test freq or the probe's specs what can one say? Some probes have very low f limits, and it varies greatly from x1 to x10. NT |
#11
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Bad probe-what's wrong?
On Thu, 24 Jan 2019 14:55:53 -0800 (PST), wrote:
On Thursday, January 24, 2019 at 5:28:49 PM UTC-5, wrote: On Thu, 24 Jan 2019 13:38:54 -0800, Paul Drahn wrote: On 1/24/2019 1:27 PM, wrote: On Thursday, January 24, 2019 at 2:23:49 PM UTC-5, wrote: I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Do you mean you're seeing more of a triangle wave with 1/5 div peak to peak? Perhaps the prob has been repaired and the wrong coax used. Probably should be 95-100 ohm. Paul I bought the probe new many years ago and have never seen any reason to repair it. There is no obvious damage. Could dropping it have caused the problem? Eric Oh, it worked in the past? Or maybe you've never had a good square wave to check it with? GH Yeah, it worked in the past using the square wave output on the 'scope. Eric |
#12
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Bad probe-what's wrong?
1. The adjustment only works in anything but x1 mode. 2. The adjustment corrects the squareness of a square wave. It makes the divider resistive. 3. Probes are designed for a certain input Z e.g. 1 M 22 || pf and freq response Make sure the scope isn't 50 ohms. 4. For the adj, the scope should be DC coupled. 5. Scope could be in UNCAL mode. Freq or voltage. 6. Check voltage with a DC source. Freq: Try the AC line for frequency. |
#13
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Bad probe-what's wrong?
On Fri, 25 Jan 2019 10:52:54 -0800 (PST), "Ron D."
wrote: 1. The adjustment only works in anything but x1 mode. 2. The adjustment corrects the squareness of a square wave. It makes the divider resistive. 3. Probes are designed for a certain input Z e.g. 1 M 22 || pf and freq response Make sure the scope isn't 50 ohms. 4. For the adj, the scope should be DC coupled. 5. Scope could be in UNCAL mode. Freq or voltage. 6. Check voltage with a DC source. Freq: Try the AC line for frequency. That DC couplng migt be the problem. It was mentioned in another post too. Tomorrow I will check things again with the 'scope properly set up and report back. Thanks, Eric |
#14
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Bad probe-what's wrong?
On Thu, 24 Jan 2019 14:53:30 -0800 (PST), Terry Schwartz
wrote: On Thursday, January 24, 2019 at 1:23:49 PM UTC-6, wrote: I got my new to me BK precision 4001A function generator and I thought I would see what it does. Tried looking at square waves but they weren't square. The probe is a Probe Master 100 MHz. So, trying 3 other probes the display shows nice square waves. Using the output on the TEK 465B 'scope itself also shows nice square waves. The display should show horizontal lines 1 division long and separated by 1.5 divisions, according to the dial settings on the 'scope. But instead the lines sweep up and down from the center and the closest points of the lines are only about 1/5 of a division apart. I tried adjusting the probe by turning the adjusting screw with an insulated screwdriver, and although it does flatten the shape some it does not fix it. So the probe must be trash but what could cause this behavior? Thanks, Eric Sounds like it's AC coupled. It is. DC didn't seem to change things but I don't know. Tomorrow I will have time to set everything properly and will report back. Thanks, Eric |
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