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Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
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Hi
Please post a picture of the screen.
Pascal
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--- In TekScopes@..., "rebelliouszombie" <santosismael@...> wrote:
Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
|
Thank you for your response. I posted some pictures in my album (rebelliouszombie_album). I don't know how to add attachments.
It's hard to see in the pictures, but the traces are wide and noisy. I notice that if I move the probes' cables around, I can decrease or increase the width of the traces. I used the oscilloscpe's square wave signal, but the same thing happens if I use a function generator.
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--- In TekScopes@..., "simoniep" <fcbtt3.nina@...> wrote:
Hi
Please post a picture of the screen.
Pascal
--- In TekScopes@..., "rebelliouszombie" <santosismael@> wrote:
Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
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Try using a coaxial probe tip adapter and your function generator or try a BNC to BNC patch cable. If moving the probe cables around affects the noise, that usually means it is being picked up by the long ground path and is not internal to the oscilloscope. On Sun, 20 May 2012 00:13:06 -0000, "rebelliouszombie" <santosismael@...> wrote: Thank you for your response. I posted some pictures in my album (rebelliouszombie_album). I don't know how to add attachments.
It's hard to see in the pictures, but the traces are wide and noisy. I notice that if I move the probes' cables around, I can decrease or increase the width of the traces. I used the oscilloscpe's square wave signal, but the same thing happens if I use a function generator.
--- In TekScopes@..., "simoniep" <fcbtt3.nina@...> wrote:
Hi
Please post a picture of the screen.
Pascal
--- In TekScopes@..., "rebelliouszombie" <santosismael@> wrote:
Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
|
Does the noise go away if you engage the bandwidth limiter (pull out the "Trig View" button)? Does it go away if you disconnect the probes and set the coupling to GND? If so, then you're just picking up high-frequency hash though the probes, which is not uncommon.
-- Mark
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--- In TekScopes@..., "rebelliouszombie" <santosismael@...> wrote:
Thank you for your response. I posted some pictures in my album (rebelliouszombie_album). I don't know how to add attachments.
It's hard to see in the pictures, but the traces are wide and noisy. I notice that if I move the probes' cables around, I can decrease or increase the width of the traces. I used the oscilloscpe's square wave signal, but the same thing happens if I use a function generator.
--- In TekScopes@..., "simoniep" <fcbtt3.nina@> wrote:
Hi
Please post a picture of the screen.
Pascal
--- In TekScopes@..., "rebelliouszombie" <santosismael@> wrote:
Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
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I posted more pictures in my album (rebelliouszombie_album). I connected the oscilloscope to the function generator using BNC adapters. The function generator is generating a sine wave at 100kHz, 50MHz, and 100MHz. You can see that the traces are very noisy.
I'll check the bandwidth limiter and the coupling and report back. Thanks.
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--- In TekScopes@..., "japh61" <japh61@...> wrote:
Does the noise go away if you engage the bandwidth limiter (pull out the "Trig View" button)? Does it go away if you disconnect the probes and set the coupling to GND? If so, then you're just picking up high-frequency hash though the probes, which is not uncommon.
-- Mark
--- In TekScopes@..., "rebelliouszombie" <santosismael@> wrote:
Thank you for your response. I posted some pictures in my album (rebelliouszombie_album). I don't know how to add attachments.
It's hard to see in the pictures, but the traces are wide and noisy. I notice that if I move the probes' cables around, I can decrease or increase the width of the traces. I used the oscilloscpe's square wave signal, but the same thing happens if I use a function generator.
--- In TekScopes@..., "simoniep" <fcbtt3.nina@> wrote:
Hi
Please post a picture of the screen.
Pascal
--- In TekScopes@..., "rebelliouszombie" <santosismael@> wrote:
Hello.
I have a Tektronix 465 with a wide and noisy trace on both channels. I cleaned the contacts on both channels and there was a slight improvement. I also fixed the coupling selector for Channel 1 (the mechanism was jammed). Everything else appears to work fine, including the triggering.
I need advice on where to start the troubleshooting. I have the original hardcopy of the service manual. Thanks for the advice.
|
No, the noise doesn't go away when I engage the bandwidth limiter.
Yes, the noise goes away when I disconnect the probes and set coupling to GND.
In AC coupling, when the probes are connected to the oscilloscope but the tips are not connected to anything, there is a trace on the display. It looks like a ripple, almost sinusoidal. When I switch to GND coupling, the trace disappears. When I switch to DC coupling, the trace reappears.
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--- In TekScopes@..., "japh61" <japh61@...> wrote:
Does the noise go away if you engage the bandwidth limiter (pull out the "Trig View" button)? Does it go away if you disconnect the probes and set the coupling to GND? If so, then you're just picking up high-frequency hash though the probes, which is not uncommon.
-- Mark
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You have a function generator that goes to 50MHz and 100Mhz? Your pictures are not labeled and it is not clear what your oscilloscope's vertical deflection and sweep speed are set to so I am not sure what I am looking at. On Sun, 20 May 2012 03:21:34 -0000, "rebelliouszombie" <santosismael@...> wrote: I posted more pictures in my album (rebelliouszombie_album). I connected the oscilloscope to the function generator using BNC adapters. The function generator is generating a sine wave at 100kHz, 50MHz, and 100MHz. You can see that the traces are very noisy.
I'll check the bandwidth limiter and the coupling and report back. Thanks.
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Under similar conditions my oscilloscopes display a noisy 60 Hz sine wave. If I connect the probe tips to the ground leads, then I see high frequency noise which varies depending on the ground lead length. On Sun, 20 May 2012 05:55:09 -0000, "rebelliouszombie" <santosismael@...> wrote: No, the noise doesn't go away when I engage the bandwidth limiter.
Yes, the noise goes away when I disconnect the probes and set coupling to GND.
In AC coupling, when the probes are connected to the oscilloscope but the tips are not connected to anything, there is a trace on the display. It looks like a ripple, almost sinusoidal. When I switch to GND coupling, the trace disappears. When I switch to DC coupling, the trace reappears.
--- In TekScopes@..., "japh61" <japh61@...> wrote:
Does the noise go away if you engage the bandwidth limiter (pull out the "Trig View" button)? Does it go away if you disconnect the probes and set the coupling to GND? If so, then you're just picking up high-frequency hash though the probes, which is not uncommon.
-- Mark
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It seems that at least the first two pictures use the same sweep knob setting, 5 us/div. Also all 4 pictures seem to show the same distortion, a square wave like distortion, synchronous to the triangle, 8(?) times the frequency. What happens with other time base settings and other amplitudes for the same triangle frequency? What happens without cabling but input set to AC or DC (not to GND)? Can you trigger on the distorting "noise"? What happens at other sensitivities?
Albert
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--- In TekScopes@..., David <davidwhess@...> wrote:
You have a function generator that goes to 50MHz and 100Mhz?
Your pictures are not labeled and it is not clear what your
oscilloscope's vertical deflection and sweep speed are set to so I am
not sure what I am looking at.
On Sun, 20 May 2012 03:21:34 -0000, "rebelliouszombie"
<santosismael@...> wrote:
I posted more pictures in my album (rebelliouszombie_album). I connected the oscilloscope to the function generator using BNC adapters. The function generator is generating a sine wave at 100kHz, 50MHz, and 100MHz. You can see that the traces are very noisy.
I'll check the bandwidth limiter and the coupling and report back. Thanks.
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The triangle was supposed to be a sine wave.
I figure out what the problem is. It was the trigger! I posted new pictures. The traces are now thin and solid. The vertical is a little off, so I guess the next step is to do a calibration.
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--- In TekScopes@..., "Albert" <aodiversen@...> wrote:
It seems that at least the first two pictures use the same sweep knob setting, 5 us/div. Also all 4 pictures seem to show the same distortion, a square wave like distortion, synchronous to the triangle, 8(?) times the frequency. What happens with other time base settings and other amplitudes for the same triangle frequency? What happens without cabling but input set to AC or DC (not to GND)? Can you trigger on the distorting "noise"? What happens at other sensitivities?
Albert
--- In TekScopes@..., David <davidwhess@> wrote:
You have a function generator that goes to 50MHz and 100Mhz?
Your pictures are not labeled and it is not clear what your
oscilloscope's vertical deflection and sweep speed are set to so I am
not sure what I am looking at.
On Sun, 20 May 2012 03:21:34 -0000, "rebelliouszombie"
<santosismael@> wrote:
I posted more pictures in my album (rebelliouszombie_album). I connected the oscilloscope to the function generator using BNC adapters. The function generator is generating a sine wave at 100kHz, 50MHz, and 100MHz. You can see that the traces are very noisy.
I'll check the bandwidth limiter and the coupling and report back. Thanks.
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The first couple of pictures showing the probe calibration square wave with some fuzz on it looks pretty normal if a source of HF noise is nearby. The width of the fuzz will change by moving the probe cables around, and engaging the BW limiter should clean it up.
You report that the trace "disappears" if you switch coupling to GND. This suggests that "Normal" trigger mode is selected. Switch to "Auto" which should produce a flat trace when the input is grounded. Is this trace clean and sharp? Then disconnect the probes and switch coupling to DC. Is this trace clean and sharp, just a little fuzzy, or really noisy?
When the probes are connected to the scope, but the tips are not connected to anything, and the input is AC or DC coupled, you may see all manner of noise, dominated mostly by your mains frequency as David mentioned earlier. This is not particularly indicative of anything other than normal behaviour.
Think about trying another signal source, even if it's just a bread-boarded oscillator. And if another scope is handy, check your function generator output.
-- Mark
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--- In TekScopes@..., "rebelliouszombie" <santosismael@...> wrote:
No, the noise doesn't go away when I engage the bandwidth limiter.
Yes, the noise goes away when I disconnect the probes and set coupling to GND.
In AC coupling, when the probes are connected to the oscilloscope but the tips are not connected to anything, there is a trace on the display. It looks like a ripple, almost sinusoidal. When I switch to GND coupling, the trace disappears. When I switch to DC coupling, the trace reappears.
--- In TekScopes@..., "japh61" <japh61@> wrote:
Does the noise go away if you engage the bandwidth limiter (pull out the "Trig View" button)? Does it go away if you disconnect the probes and set the coupling to GND? If so, then you're just picking up high-frequency hash though the probes, which is not uncommon.
-- Mark
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David Hess