Re: Tek 7854 intermittent issues
On Thu, Sep 3, 2020 at 06:32 PM, Chuck Harris wrote:
Randomness doesn't exist in the digital logic world.
Some would argue randomness doesn't exist - full stop, nor does a digital world. Thanks for that, Chuck. So the 7854 uses (pseudo) random sampling? If something is wrong with the pseudo random generator, i.e. repeating partial sequences a few times, then continuing, that could explain the repetition of the garbling that I thought I saw. And doesn't it show that AQR takes far too long and just repeats until finally meeting acquisition complete criteria or thinks it meets them and doesn't? That's not an acq. RAM or DAC problem. That looks more like a random address generator/acquisition-complete problem. BTW, I just noticed a similar 3/sec or so slight brightness flare in the steady-state display. Video artifact or Z-modulation? Power supply? Raymond
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Re: Tek 7854 intermittent issues
Most humans are a lot more random than a PRNG! :)
David
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Chuck Harris Sent: 03 September 2020 17:32 To: [email protected]Subject: Re: [TekScopes] Tek 7854 intermittent issues : : The randomness of the human operator relatively to the PN generator will make it appear truly random. -Chuck Harris
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Re: Tek 7854 intermittent issues
Randomness doesn't exist in the digital logic world.
The scope knows how many pseudo random numbers it takes
before the pseudo random sequence repeats, and waits
that long...
From the operator's perspective, it is random, because
the operator has know idea where the scope will be in
the pseudo random sequence when it starts a new capture.
The randomness of the human operator relatively to the
PN generator will make it appear truly random.
-Chuck Harris
Raymond Domp Frank wrote:
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On Thu, Sep 3, 2020 at 08:33 AM, Nick Corvid wrote:
and since parts are missing it won't complete
How does the 'scope decide AQR is complete, if samples are taken randomly, out of order? Or are they not taken randomly, just at a slow pace, just at subsequent scans? I guess it's RTFM-time again for me.
Raymond
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Re: Tek 7854 intermittent issues
On Thu, Sep 3, 2020 at 08:33 AM, Nick Corvid wrote:
and since parts are missing it won't complete
How does the 'scope decide AQR is complete, if samples are taken randomly, out of order? Or are they not taken randomly, just at a slow pace, just at subsequent scans? I guess it's RTFM-time again for me. Raymond
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Re: Tek 7854 intermittent issues
On Thu, Sep 3, 2020 at 05:32 PM, Raymond Domp Frank wrote:
This all seems to happen without human intervention.
Ouch, it happened again! Nick tells us about his intervention so that part of my answer falls through (RTFM). The repetitiveness in the random garbling remains though (I guess...) Raymond
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Re: Tek 7854 intermittent issues
On Thu, Sep 3, 2020 at 04:43 PM, Albert Otten wrote:
Could be a digitizer problem but also RAM problem I think.
I've only superficially followed parts of this thread and now watched the video. It's normal that during acquisition, the readout characters are being garbled in a way that looks random, we know that. The video however seems to show a repetitive pattern with a repetition frequency of about 3 Hz for a rather long time, the waveform display is updated, then proceeds to "stop" (sort of), next "busy" is displayed and the procedure seems to continue a few times until it finally comes to a stop, showing the correct waveform. This all seems to happen without human intervention. To me, that doesn't look like a data (RAM, digitizer) problem but rather a "randomizer/stop/ready" criteria problem. I have no idea about the internals of that in the 7854. "Randomizer" because of the random sample acquisition in the 7854. Raymond
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Re: My P7001 connected to a modern PC - need more infos about the original
Hi Holger,
Nice work! I like the idea of giving commands via that keyboard at the scope in stead of the PC. Perhaps I will do similar with my 7854/GPIB. So far I gave commands via the PC, but the PC program could just as well wait for a command number from the 7854 (via SENDX).
I have a few kilos TEK SPS Basic manuals. These were used with my 7704A/P7001 and CP controller in a previous life but are not specific for that DPO I think.
Albert
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Re: Tek 7854 intermittent issues
Hi Nick, I watched your video and again some earlier videos and photos. As far as I can see your calibrator is OK in analog mode? Photo _MG_2320 in /g/TekScopes/album?id=252782 shows 40 mV amplitude in analog mode. But in AVG photo _MG_2318 the amplitude is 20 mV; also mainly 20 mV in _MG_2323 except for an "outlier" and the right most part. You didn't show where the zero level is. My guess is that the zero input values are digitized to 20 mV in stead of 0 mV. Except for the "outlier" and right most part where correctly 0 mV is displayed. If you repeat things with the calibrator at 0.4 V or 4 V and the scope at 0.1 mV/div or 1 V/div you might see other anomalies. Could be a digitizer problem but also RAM problem I think. Albert
On Thu, Sep 3, 2020 at 09:55 AM, Nick Corvid wrote:
Alright, sorry for the quality I had it on the bench rather than in a rack so
my angle is quite bad (looking down from the top) but, I have a video of the
behavior!
Video:
If you have time watch the whole thing, it shows some strange artifacts as it
goes, if not have some time stamps of the more interesting things.
Immediately after power up: 00:00
Switch to stored: 00:05
Start of first AQR: 00:08
Things start happening: 02:11
End of first AQR: 02:25
Final result after 3 more AQR's: 02:32
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My P7001 connected to a modern PC - need more infos about the original
Hi everybody!
I've managed to connect my DPO to a modern PC - here is a video of the working system:
This is the overlay-card I'm using:
To get the look & feel correctly I need some more input ;-)
Does anyone have any information about the programs which were available with the DPO?
Listings, printouts, descriptions, pictures, own experiences, ...?
I've shared all my information about the system on the tekwiki page:
Thanks
Holger
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Re: Tek 7854 intermittent issues
Ah, I meant Hi Paul (not Nick) in my previous message. Albert.
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Re: Tek 7854 intermittent issues
Hi Nick,
My 7854 is an earlier version. Strange, if that makes any difference I would expect the newer version to have a faster sampling rate.
Albert
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On Thu, Sep 3, 2020 at 04:48 AM, Paul wrote:
Albert -
Yep, those are the steps I'm following. Oddly though, my 0.5ms/div works as
reported at 512 P/W, and fails gracefully as described at 0.2ms/div, but at
1024 P/W, it works at 2ms/div & fails at 1ms/div. I never get the immediate
error. I've got a 'newer' model w/ combined RAM/ROM board, you?
Nick -
Happy to poke around & take readings for ya - let me know if I can be of help.
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Re: Tek 7854 intermittent issues
Alright, sorry for the quality I had it on the bench rather than in a rack so my angle is quite bad (looking down from the top) but, I have a video of the behavior!
Video:
If you have time watch the whole thing, it shows some strange artifacts as it goes, if not have some time stamps of the more interesting things.
Immediately after power up: 00:00
Switch to stored: 00:05
Start of first AQR: 00:08
Things start happening: 02:11
End of first AQR: 02:25
Final result after 3 more AQR's: 02:32
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Dennis,
I¡¯m very thankful for this online community, especially now. I miss Stan, one of the originals.
Thank you!
George
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On Sep 2, 2020, at 4:11 PM, Morris Odell <vilgotch1@...> wrote:
Thanks for the mention Dennis and your efforts as a moderator. I've really enjoyed being a member of this group and look forward to the daily digest I receive. The knowledge and helpfulness of the other members here is a great resource. I also enjoy helping other when I can too.
I hope this group continues for a long tiome to come!
Morris Odell VK3DOC locked down in Melbourne, Australia
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Re: Tek 7854 intermittent issues
It seems like my issue might be thermal related. When it cold starts (everything is at room temperature) it almost always is missing parts of the digital waveform, but if I set it to AQR (and since parts are missing it won't complete) and watch it in stored mode, after a few minutes the missing parts start to fill with noise then the correct data starts to fill in a short while after that, once that has occurred, it seems (most of the time) that the digital side will capture properly until I turn it off and it cools down for a while again. When I'm able I'd like to capture a video of this in action to better describe what's happening.
Also I genuinely didn't know you were supposed to use a specific plugin for AQS until just now, when I very first set up this machine to test it, it would AQS for anything, in auto trigger mode, using just a 7B85 in the left horizontal slot, at any time per div I selected. When this stopped I thought there was an issue.
Finally have the power supply slid out as well so I can finally make some measurements to see if I'm getting some noise or something that's messing with everything until it's "warmed up". Though the fact that the issue disappears randomly makes me not very confident in any correct looking readings.
Still have some occasional other issues as well, like the cal out reading (both on the scope and on another scope) around 2.6 times what it should, but only for a few minutes and SUPER intermittently (like I might not see it for 20 or 30 power cycles or more)
This thing causes me great confusion.
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
Oh and you might want an extender cable too, for when you need to repair it (and you will).
I recommend you read the circuit description of the manual and study the schematics.
Use this PDF
Text-searchable and nice clear schematics and graphs.
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Re: Tek 7854 intermittent issues
Albert -
Yep, those are the steps I'm following. Oddly though, my 0.5ms/div works as reported at 512 P/W, and fails gracefully as described at 0.2ms/div, but at 1024 P/W, it works at 2ms/div & fails at 1ms/div. I never get the immediate error. I've got a 'newer' model w/ combined RAM/ROM board, you?
Nick -
Happy to poke around & take readings for ya - let me know if I can be of help.
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
I believe it, Harvey.? A former coworker had experimented with tubes, and he said that while you can run the filaments from A.C., try D.C. for audio; you'll like it.Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Harvey White <madyn@...> Date: 9/2/20 7:01 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 1S1 sampling unit; (also 7B53AN & 7A18 plugins) I once had a Heathkit OM3, which had a horrible hum problem (eventually).? I solved it by running the filaments off DC.? If you ever have that problem, I can suggest it.? The IO-14 was billed as a lab scope, I think.HarveyOn 9/2/2020 9:19 PM, David Collier wrote:> Hi Garth,> I'm in Canberra (Oz).> Some US sellers won't ship to Oz, a few charge ridiculous shipping of US$400 to 500, which is where they hope to profit!> A Heathkit IO-14 from USA is costing me US$50 carriage via the Global Shipping Program, which seems very inexpensive.> David C.>> >>
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
I once had a Heathkit OM3, which had a horrible hum problem (eventually).? I solved it by running the filaments off DC.? If you ever have that problem, I can suggest it.? The IO-14 was billed as a lab scope, I think.
Harvey
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On 9/2/2020 9:19 PM, David Collier wrote: Hi Garth,
I'm in Canberra (Oz).
Some US sellers won't ship to Oz, a few charge ridiculous shipping of US$400 to 500, which is where they hope to profit!
A Heathkit IO-14 from USA is costing me US$50 carriage via the Global Shipping Program, which seems very inexpensive.
David C.
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
Thanks Thomas,
Happy to swap my HP1740A for a Tek!
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
Hi Garth,
I'm in Canberra (Oz).
Some US sellers won't ship to Oz, a few charge ridiculous shipping of US$400 to 500, which is where they hope to profit!
A Heathkit IO-14 from USA is costing me US$50 carriage via the Global Shipping Program, which seems very inexpensive.
David C.
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Raymond Domp Frank
David C. Partridge
Glydeck