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Re: 2247A occasional horizontal jitter
Hi.
To me, that flickering extra tail at the right end of the B sweep trace, does indicate that the A sweep is being triggered at two different points.? But, the B sweep trigger seems fine with a nice stable image. Do you have the service manual for that 'scope? Regards. Dave G8KBV -- Created on and sent from a Unix like PC running and using free and open source software: |
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Re: 2247A occasional horizontal jitter
Looking at the screen scope could be in delayed B sweep, we need B-trigger (not delayed). I don't have the exact scope but looking at the picture of the front panel:
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1) Mode needs to be "B". You may need to rotate time/div knob one click in clockwise direction after selecting "B" to be in B-sweep 2) Trigger needs to be "B" trigger by pushing A/B select in trigger area and selecting "NORM" in B side.? If you take another video seeing the setting is useful. B trigger has almost the same exact blocks like A trigger but it is a different path. If they both behave the same, the issue is in the common path between them, or supplies/reference voltages. Ozan On Sat, Jul 15, 2023 at 09:36 AM, Alex wrote:
NOTE: PLEASE DISREGARD THE PREVIOUS 2 POSTINGS, i HAD TO DELETE THEM AS THE LINK TO THE VIDEO WAS SOMEHOW COMING OUT WRONG. |
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Re: 2247A occasional horizontal jitter
If you go up north from test point 3C you will see R430, then go right and you will find R432.
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I also see C432 just above R430. R445 is a little above test point 3D. C444 is right of test point 3D. Ozan ===== On Sat, Jul 15, 2023 at 10:37 AM, Alex wrote:
I've been looking into the service manual, and looking up the most convenient connection point to U421C pins 25/26, like any associated components connected to each of those pins. where it should be easy to hook the scope probe to. |
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Re: 2247A occasional horizontal jitter
I've been looking into the service manual, and looking up the most convenient connection point to U421C pins 25/26, like any associated components connected to each of those pins. where it should be easy to hook the scope probe to.
According to the component locator list, IC421 is located at location 3F on the A10 board component layout. Located. Turns out pin 25 is connected to R447, R448, and C447. I've also located those components already in the same 3F area. Pin 26 is connected to R432, R445, C432, and C444. But these components are supposedly located at area 2L of the board. But I am unable to locate any of these components at 2L, perhaps a mistake in the manual? Also looked at 3F around IC421, where I would rather expect them to be, but don't see them there either. And it does not help that in both copies of the service manual that I have, the A10 board component layout is quite low resolution. So at even at 3:1 mag it starts to get grainy which makes it difficult to read the component labels. My SM copies came from the links posted earlier, which turned out to be the ones I already had on file. Anybody have a better resolution image of A10 component board layout? |
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Re: 2247A occasional horizontal jitter
NOTE: PLEASE DISREGARD THE PREVIOUS 2 POSTINGS, i HAD TO DELETE THEM AS THE LINK TO THE VIDEO WAS SOMEHOW COMING OUT WRONG.
In the mean time I tried B-sweep test, again with signal being same 1KHz signal.. I waited on A-sweep to see the waveform starting to jump and then switched to B-sweep. The result is the right side very end of the waveform tail sort of slightly growing and getting shorter again. The wave form itself stays absolutely steady and does not move. Not really sure what this result means in terms of overall troubleshooting. The described B-sweep effect can be seen on this 8 second video: https://miwww.com/tmp/2247A_jitter2.mp4 MP4 video file is about 15MB. |
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Re: 465M won't trigger
Hi.
It could be a simple bad interconnect between boards/cables etc.? I recall from my time at Tek, that some of those semi-gold plated "Harmonica" connectors would become intermittent over time. You moved it about when fitting the substitute board, and it all worked.? Now, things have "relaxed" a bit over time, and gone faulty again. Try a gentle poke (with an insulated stick) at the boards and interconnects and see if anything shows itself as a culprit. 73. Dave G8KBV. -- Created on and sent from a Unix like PC running and using free and open source software: |
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Re: 465M won't trigger
so frustrating to have the same problem again with it just sitting in my shop.
I have a shop full of test equipment that sometimes I just cannot get to the bottom of the problem so it gets moved to the side for an easier repair on another unit. But then get back to it later when you have more mental space to look deeper into an issue. I like the 465M as there isn't to much of an issue of a transistor coming loose in a socket since all parts are soldered into the board. ?I have spent days trying to pin down issues on vintage equipment like many members of this group but here is where you hopefully get some help. ?Do some PS checks and advise your findings along with cycling all push buttons to help clear any oxidation. Craig |
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Re: 465M won't trigger
Larry Tusoni W6YH
¿ªÔÆÌåÓýHi Craig Great thanks. You know I did check at least some of the voltages according to the manual before I installed the replacement trigger board so It is probably a good idea to do it again before I use it for target practice! ;-) I loved the scope and it has worked for me for 20+ years so hate to be without it but it is so frustrating to have the same problem again with it just sitting in my shop. Regards, Larry
-------------------- Among God's creatures two, the?dog and the guitar,? have taken all the sizes and all the?shapes, in order? not to be separated from the man. -- Andres Segovia ? Larry's Personal Email Amateur Radio: W6YH larry@...? 209.736.9197 Angels Camp, California Earth-Planet, Universe |
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Re: 465M won't trigger
¿ªÔÆÌåÓýit won't trigger again just like beforeLarry,? My thought is there probably is something up with the power supply. ?Ive worked on a bunch of these and the can caps seem to fail or get marginal on the power supply rails. Its pretty easy to check power supply voltages. Remove top cover and there is three DC power supply posts along with the ground post just behind the 115 vac power switch. ?you can also check the 95v opposite side just in front of the aluminum barrier. ?Connect DVM to common and each tap measure DC, then switch meter to AC and check again for voltage. ?This should help you get an understanding if power supply is problem. Craig On Jul 14, 2023, at 12:26 PM, Larry Tusoni W6YH <larry@...> wrote:
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Re: 2247A occasional horizontal jitter
On Fri, Jul 14, 2023 at 08:46 AM, Alex wrote:
=== U421C pins of the bad scope measured with the good scope. Ozan |
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465M won't trigger
Larry Tusoni W6YH
My 465M would not trigger a few months ago so I found a used trigger board and installed it and it worked fine.
I haven't used it since then, and today, it won't trigger again just like before. It has been stored in my humidity/temperature controlled shop so I am not sure how this can happen so any ideas would be appreciated. Thanks, Larry |
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Re: 2247A occasional horizontal jitter
Just a heads up, wont be able to get to the scope until Sunday to do the additional testing with B-sweep. But if I am able to do so before I'll post results earlier.
As somebody suggested the waveform "jump" might be coming from the generator itself, I tested the output (simultaneously with a BNC T adapter) both with the 2247A and the 2465B, and the jump only happened in the former. So that would tell me the problem is not coming from the generator. Or is it perhaps not happening in the 2465B just because it has better trigger capabilities? Not sure that is what someone was aiming at, so wanted to make sure to put this out again to clarify. About "On the second scope use channels 2 and 3 to look at U421C (sheet <3>) pins 25 and 26." In this case the "second scope" I am using would be the 2465B, so not sure if you rather meant those test point instruction measurements to be TAKEN with the "second scope" instead of "ON the second scope"? BTW the link to the short video should be good again: |
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Re: 2247A occasional horizontal jitter
Ozan wrote:
> It may not give any immediate clues but you can try B-sweep with sine wave and see if the jump is there in B-trigger too. B side is very similar to A trigger. Ha, good idea! I think trigger level in 2247A is analog so, if A-sweep trigger level setting itself is the culprit, B-sweep will be OK. A and B triggering are independent, of course. Unless trigger level reference (supply) is the culprit, since that¡¯s probably common to both.? Raymond |
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Re: 2247A occasional horizontal jitter
It may not give any immediate clues but you can try B-sweep with sine wave and see if the jump is there in B-trigger too. B side is very similar to A trigger.?
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Since you have other scopes, you can feed in same sine wave to both this unit and a second scope, and trigger both with same sine wave. On the second scope use channels 2 and 3 to look at U421C (sheet <3>) pins 25 and 26. Pin 26 is the final result of trigger processing and pin 25 is the trigger level. If one of them jumps vertically (on the second scope it won't shift horizontally) then you can trace back from that point. If they both look stable issue most likely is downstream from U421C. Ozan ===== On Wed, Jul 12, 2023 at 07:41 AM, Alex wrote:
Ozan: |
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Re: 2247A occasional horizontal jitter
On Sat, Jul 8, 2023 at 05:31 PM, Alex wrote:
I noticed this a few weeks ago, that after about 10-15 minutes I see an occasional horizontal jitter that lasts just for about half to 1 second, and then does not happen again until about another 30 or 60 seconds, sometimes more, sometimes less (no constant rhythm).David, OP's above text precludes the presence of what you write with "If so, there might be an intermittent HF spike sometimes on the sine wave from the generator." because the "shifted" situation lasts for a short while. In actual fact, I'd call it more a hopping than a jitter. Ozan: The OP does not understand what you're looking for with triggering in Normal mode. I also described it: In Normal mode, with trigger level setting temporarily outside peak values because of level "jitter", no trace, so playing with the level, trace should be flashing irregularly because of level shift. Raymond |
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Re: 2247A occasional horizontal jitter
Ozan:
yes the jitter is still there when feeding a sine wave and trig mode set to NORM. Dave: Yes both sine and square wave signals are from the same generator which really has two independent outputs (Heathkit IG-18). I also simultaneously verified the output of the generator with my other scope and the jitter is only shown on the 2247A. Yes the jitter is still there when feeding a 1Khz sine wave, and with HF Reject trigger mode. To me the 2247A is the best scope, tremendously flexible and feature rich with lots of CPU driven useful measurements. It gets picked first on 95% of the cases. The 2265B usually just because higher than 100MHz bandwidth is required, or to quickly cross check something. I also have a 222, and a 2213A, but those really don't get used much. I've had the 2247A now for 11 years, got it used off ebay and all it needed back then was to replace the internal Lithium battery that only stores the last used configuration. |
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Re: 2247A occasional horizontal jitter
Hi Alex.
As you said there is no jitter when looking at and triggering from a square wave signal, I doubt that an overall PSU issue would be the cause. Tracing the trigger level/setpoint signal back to it's source (if available) might be a worth while task and looking at that for any noise/jumps etc. Also...? Are the two waveforms (Sine and Square) from the same generator? Another idea, with a LF (Audio frequency) sine wave, use "HF Reject" mode for the trigger and see if that fixes it. If so, there might be an intermittent HF spike sometimes on the sine wave from the generator. I do not have a 2247A here, just a couple of older 400 series units (465 and 468.) From what I can gather, the 2247A is an analogue 'scope, but digitally controlled.? When I get a bit more time, I'll pull a copy of the service manual from the web. I do have a fair bit of experience with Tek scopes though, as I worked for them in the UK many years (several decades) ago, when the 465/475 and 7000 series etc were current products. I was performing in-house service for customer returns, warranty and non warranty, plus calibrations before being moved onto the Spectrum Analyser or "FDI, or Frequency Domain Instrumentation" product line and accessories. ('Scopes of course being "Time Domain Instruments".) The 492P was "New" just before I left, due to unfordable (to me) accommodation in/near Maidenhead UK, where they moved the high end service operation to from Harpenden where I was first located.? At the time, I lived about midway between the two sites, and was told I could not go back to Harpenden. The years since then have been occupied working with a very diverse range of electronic, electrical and RF kit, to component level. (Digital, Analogue, DC to microwaves, mW to many 10's of kW, and associated accessories plus test/monitoring/analysis instrumentation.) Thankfully, now retired...? I loved the work, but not the office politics in recent times. Best Regards. Dave B (Ex Tek UK.) -- Created on and sent from a Unix like PC running and using free and open source software: |
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Re: 2247A occasional horizontal jitter
On Wed, Jul 12, 2023 at 07:44 AM, Ozan wrote:
Your observation of sine vs square suggests trigger level jumps up/down. On a square wave edge is fast so even if trigger level moves horizontal jump will not noticeable.?Perhaps the OP gets it and accepts it when you write that, Ozan, instead of just hunting for glitches on the DC power supply or suspecting "...the horizontal PLL losing its lock". Raymond |
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Re: 2247A occasional horizontal jitter
Your observation of sine vs square suggests trigger level jumps up/down. On a square wave edge is fast so even if trigger level moves horizontal jump will not noticeable.?
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In "AUTO LVL" mode a peak-to-peak detector sets the two extremes of the trigger level. If there is a problem with peak detectors trigger level will move. In NORM mode trigger level is based on the position of the level knob. Just testing sine wave in NORM mode is enough to rule out peak detectors. Ozan -------? On Tue, Jul 11, 2023 at 10:06 PM, Alex wrote: On Mon, Jul 10, 2023 at 01:07 PM, Ozan wrote: |
Craig Cramb
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