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Thanks Mark. I tried CH1 trigger and LINE trigger and the waveform is exactly the same. Also there are tiny spikes in the waveform, do I measure those or just the center band of the waveform?
Attached are some example waveforms and my results below:
J119 Pin Vdc p-p ripple (with spikes, without spikes)
1 -14.95 8mw, 4mv
2 4.98 35mv, 20mv
4 9.96 8mv, 4mv
5 -4.96 10mv, 7mv
6 14.92 8mw, 5mv
8 86 10mv, 8mv
9 41.7 8mv, 6mv
11 -7.99 8mv, 4mv
12 4.96 15mv, 5mv
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Another approach is to use a DMM set on AC volts. This will measure the total p-p ripple up to the frequency limit of the DMM. As long as that's 20kHz or higher, it will catch any poorly performing filter caps that are need of replacement.
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Thanks Mark. I tried CH1 trigger and LINE trigger and the waveform is exactly the same. Also there are tiny spikes in the waveform, do I measure those or just the center band of the waveform?
Attached are some example waveforms and my results below:
J119 Pin Vdc p-p ripple (with spikes, without spikes)
1 -14.95 8mw, 4mv
2 4.98 35mv, 20mv
4 9.96 8mv, 4mv
5 -4.96 10mv, 7mv
6 14.92 8mw, 5mv
8 86 10mv, 8mv
9 41.7 8mv, 6mv
11 -7.99 8mv, 4mv
12 4.96 15mv, 5mvOn your photo of pin 2, it looks like about 30mV p-p total ripple and maybe 10mV 2x line ripple. On pin 4, about 7mV total and I can't see any 2x ripple.
The total p-p ripple would have components from the AC line and also the switching power supply which runs at approx. 20kHz. The tiny spikes in your pin 4 photo don't correspond to that, or 2x the line frequency. But even if you count them, you are still well under the total p-p ripple.
It's a somewhat subjective series of tests, as you are trying to visually average the trace on the screen. A digital scope could do it for you now-a-days, but I don't think that's what the authors had in mind.
Another approach is to use a DMM set on AC volts. This will measure the total p-p ripple up to the frequency limit of the DMM. As long as that's 20kHz or higher, it will catch any poorly performing filter caps that are need of replacement.
The tiny spikes might be common mode noise. You can check by probing pin 7 or 14 on J119. This is GND and if you still see the same noise, it's going to be visible in all your measurements.
Thank you all so much. I have my order ready. It's definitely more than I was hoping to spend. I checked the hours with EXER 05 and the scope has 5000. Is there a particular point when a full recap is truly necessary? Or can I get away with just changing the SRAM battery and the RIFA caps? Is checking the ripple important to make this decision? I also took a video of EXER 02 as recommended by many here. Also any help on the proper/best points to attach a temp battery to the SRAM will be greatly appreciated.
....I get a dreaded error message: CT TEST 84 FAIL 0C. I didn't even touch or disconnect any components. All I did was remove the case, probe J119, and put the case back on.
Hope this isn’t too much of a newbie request but Im having a hard time finding any good instructions online with videos or pictures on how to check p-p ripple and 2x line frequency ripple using an analog scope. I think the p-p ripple is just the measurement of the max top and min bottom of the waveform across the screen. See my zoomed in picture of pin 2 with annotations. But I can’t seem to figure out the 2x line frequency number which is a very small number for most pins in table 5-1. I also did check the ground pins 7 and 14 for noise and here is the result. Seems like minimal noise of less than 1mv.
Use line triggering to make the ripple measurement.
Hope this isn’t too much of a newbie request but Im having a hard time finding any good instructions online with videos or pictures on how to check p-p ripple and 2x line frequency ripple using an analog scope. I think the p-p ripple is just the measurement of the max top and min bottom of the waveform across the screen. See my zoomed in picture of pin 2 with annotations. But I can’t seem to figure out the 2x line frequency number which is a very small number for most pins in table 5-1. I also did check the ground pins 7 and 14 for noise and here is the result. Seems like minimal noise of less than 1mv....I've also included some shots of the same pin on an analog scope (actually the same 2465 measuring itself). It's a subjective call where to place the p-p cursors and I'm not including the extreme outliers. For the 2x line ripple, it may help to set up the cursors as shown for 120 Hz, so you know what periodicity you're looking for in the envelope.
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Wow thank you so much for the explanation. I'm almost there. Would my attached picture be a proper yet subjective interpretation of your 2x frequency ripple? I added two black lines comparing the two peaks at 120hz apart. They are about <1mv apart.
You're welcome! Sorry I didn't get a chance to post back sooner.
...Again the measurement on the analog scope is very subjective, but in the photo it's in the right ballpark and maybe the upper cursor should be a little higher. If the ripple was near the limit, in this case 30mV, you would clearly see the deviation in the envelope. With some of the other rails on J119, it's just going to be impossible to see their limits of a mV or two.
It would have been nice if Tek provided more than a half a sentence or an example of what they intended.
...Again the measurement on the analog scope is very subjective, but in the photo it's in the right ballpark and maybe the upper cursor should be a little higher. If the ripple was near the limit, in this case 30mV, you would clearly see the deviation in the envelope. With some of the other rails on J119, it's just going to be impossible to see their limits of a mV or two.
It would have been nice if Tek provided more than a half a sentence or an example of what they intended.I too have been thinking about this test and what the Tek engineers really wanted. I want to propose another interpretation. Could they have wanted us to measure the p-p ripple at 2 points 120hz apart and subtract the two voltages? See the pic attached. Point A has a p-p of 24mv. Point B (120hz later) has a p-p of 23mv. So the p-p ripple at 2x the line frequency would be 24-23=1mv.
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Ive come across 3 new issues with my scope that I wanted to share with everyone:
1. The voltage readings appear a bit off from my other scope and a tektronix signal generator I have. If I set the generator for a sine or square wave with 20v amplitude (the max for the generator) my other scope reads them as 20v but the 2465A reads 21.5V. Unfortunately the 2465A doesn’t have the cool measurement function that the 2465B has to double check the voltage reading. Btw any way of adding that feature to a 2465A?
2. The trace comes and goes as the unit warms up. Sometimes it disappears completely. This seems to fix itself after it warms up. Still testing to make sure. Adjusting the readout knob doesn’t help.
3. My focus knob is set to 3 oclock in order to be in focus. I would think a properly functioning scope would be closer to 12 oclock.
I have not heard of any way to upgrade an A to a B. The A1 board in the B has some additional hardware dedicated to the parametric measurements.
I have not heard of any way to upgrade an A to a B. The A1 board in the B has some additional hardware dedicated to the parametric measurements.
There's a fleabay seller that allegedly converts 2445b into 2465b. Allegedly comes complete with "do not tamper" stickers, so that if you spot his perfidy he can refuse to refund money.
Have you checked the other vertical ranges for accuracy? Are they ok or off by the same percentage? Do the cursor readings match the graticule?
Is it fading out and then back in, or does it suddenly disappear and reappear?
The readout knob? Does the readout fade, or did you mean the trace intensity knob? Or do you mean everything disappears?
Maybe it's heat related? Perhaps a session with a can of freeze spray (or inverted canned air) might provide some clues.
I have a 2465 and a 2445A and neither of my focus knobs sit at 12:00. They're both around 2:00.
There are additional adjustments you can try, and all in combination with each other because they interact. The front panel ASTIG for one, and on the HV board there is HIGH DRIVE FOCUS, and depending on your serial number, there might be an EDGE FOCUS. This is covered in the adjustment procedure.
It takes some patience to iterate for the best focus. I've found it difficult to get everything on the screen in perfect focus and it usually ends up being a compromise.
I'd recommend marking the current pot positions with a fine Sharpie before tweaking.
I meant that when adjusting the readout intensity knob it didn't affect it. The trace intensity knob does correct it temporarily, but it then corrects itself. Meaning if the trace starts dimming and/or disappears
if I immediately set the trace intensity knob to compensate for the dimming it will brighten up, but then in a few seconds it corrects itself and become super bright. Maybe the pot for this knob needs to be cleaned?
Have you checked the other vertical ranges for accuracy? Are they ok or off by the same percentage? Do the cursor readings match the graticule?The generator is a Tek CFG250. It was a switch for either (i) up to 2V or (i) up to 20v amplitudes, so I tried both and maxed the anplitude setting in hopes it would read exactly 2V and 20V. Both voltages have the same problem by the same percentage and even across different vertical ranges of the scope. If it wasn't for my other scope reading the generator as accurate at 2v and 20v, I would probably assumed it was the generator that was off. The cursor readings match the graticle. To make matters more confusing the calibration point on the scope does read accurately at .4v.