Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 18590914 times)

salvagedcircuitry and 89 Guests are viewing this topic.

Online vk6zgo

  • Super Contributor
  • ***
  • Posts: 7717
  • Country: au
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110425 on: January 05, 2022, 01:46:30 pm »
This Tektronix TM500 standalone module just popped up.  No idea what it is.. so just in case it's something interesting and rare someone might be interested in ?!

https://www.leboncoin.fr/outillage_materiaux_2nd_oeuvre/2036581441.htm

There is no model number written on the face plate somehow ?! So I can't even look it up on Tekwiki ! :-//

Face plate is in French. Says it's an " Ausculteur Dynamique ".  "Dynamic" something... meh !  :-//



I dived down the rabbit hole, & it can be either to do this:-
https://www.ifsttar.fr/fileadmin/user_upload/editions/lcpc/MethodeDEssai/MethodeDEssai-LCPC-ME70.pdf

or this:

 
The following users thanked this post: Vince, mnementh

Offline BU508A

  • Super Contributor
  • ***
  • Posts: 4541
  • Country: de
  • Per aspera ad astra
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110426 on: January 05, 2022, 01:54:46 pm »
Prototype eagerly awaiting it's OCXO

 ;D

They are on their way. In theory, they should arrive by tomorrow.
Friday, if tomorrow is a holiday in your area.
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
The following users thanked this post: ch_scr

Online vk6zgo

  • Super Contributor
  • ***
  • Posts: 7717
  • Country: au
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110427 on: January 05, 2022, 02:02:44 pm »
: when the picture turns to B&W... I notice that I can make it go back to colour if I fast forward just a few seconds. Then I fast rewind a few seconds to go back to the part of the movie that was previously B&W and now... oh magic it's in coiour now !  So that means the tape itself is not the problem I guess.... must be the VCR doing something funny.

I am pretty sure it is false triggering on turning the color decoder on when you wiggle it that way. If you look at the color picture you attached, it is evident the colors are wrong and color interferrence can be seen in form of a mesh, also visible on top of the black frame bars.


I don't understand any of what you say, I don't kn,ow my VCR stuff  :(

But do I sense that you agree that the problem might that the tape is not guided and/tensionned properly ? After wigglijg it a bit using Fast forward/rewind, I had no more B&W ruin my viewing for the entire movie !  :D 
So I guess the tape was not properly positioned on the drum, and wiggling it brought it back where it should be.
I guess when in playback mode, it's a bit loose and wanders about. Might also (?) explain another issue I am witnessing : very blurry/fuzzy picture, like it's way out of "focus", say. Also very unstable, it's moving up and down all the time, randomly, but incessantly.

I guess could be worse playing with the mechanical adjustments responsible for positioning and tensioning (is that a new word ? Firefox chokes on it...) the tape ? Don't don't how to do that, need to do some reading...

I did watch a few VCR repair/service videos on " 12votlvids " YT channel. Will watch his VCR vids again to refresh my memory....

The blurry/fuzzy picture is probably due to the limitations of the consumer/home VHS machines, if I remember correctly from the TV programme "Secret Life of Machines" you only got about half the quality of a live TV broadcast from a VHS tape, as only half the information (lines) are recorded, commercial video recorders must have been different.
Also older LCD TV's tend to make standard definition analogue content look even worse, even digital TV looked blocky & crap of the last dumpster find TV I had.



David

This post was "recorded on sticky tap & rust".  :-DD

Easy,----- "The secret Life of Machines" lied!--

Edit:Actually they didn't, you just "got the bull by the horns!"
Even fast forwarding through the first bit, that's about 20 minutes of my life I'll never get back ----AAaaarrrrgggghhh!

Home VCRs recorded all the lines, but the reason for a reduction in quality was mainly that the video bandwidth was reduced due to some other compromises in the design.

I also found that pre-recorded tapes varied quite a lot in picture quality, ---"off air" tapes, much less!

When we first got a VCR, I was watching a football game, (Australian Rules Football, or Cricket on a nice sunny day are good "standards" to go by) so simply recorded some of that, so, whilst the "footy" was on, I could switch back & forth.

The taped version was definitely not as high in resolution, but was quite acceptable.
« Last Edit: January 05, 2022, 02:27:51 pm by vk6zgo »
 

Offline Neper

  • Frequent Contributor
  • **
  • Posts: 543
  • Country: de
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110428 on: January 05, 2022, 02:17:10 pm »
And you accuse Vince of being a drama llama.

No, that was me.  ;)
If I knew everything I'd be starving because no-one could afford me.
 
The following users thanked this post: mnementh

Offline Vince

  • Super Contributor
  • ***
  • Posts: 4247
  • Country: fr
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110429 on: January 05, 2022, 02:17:39 pm »
Hey Vince,

look, what I've found!
Some nice R&S gear, not that expensive!   >:D

https://www.ebay-kleinanzeigen.de/s-anzeige/rohde-schwarz-opf-videometer/1979156337-168-5586



As always: NAWTS


Not interested !  ;D

I am not into video broadcasting, vectorscopes ahve no use for me...

I just like looking at the odd video signal on my scope for fun, when an opportunity to do so arises, like with this VCR, but that's about as far as it goes ! ;D

And 100 Euros is twice my usual budget for old stuff, I am not rich...  I target 50 Euros or so. If a piece of TE is up to 50 Euros and I have a crush on it, I can do an impulse buy... but at 60 or 75 or a 100, I have to go through a rigorous plus/minus analysis to decide if it's worth it or not !  ;D   

 

Online vk6zgo

  • Super Contributor
  • ***
  • Posts: 7717
  • Country: au
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110430 on: January 05, 2022, 02:41:01 pm »
Mouarf.... trying to fix a VCR, first one in my life, never worked on these things before...
It was given to me and I thought hell, would be cool to (try to...) fix it as an exercise and to have at least one VCR around, you never know when you might need one... seeing as I tend to like old stuff, who knows, might come handy one day.

Anyway. First it did not power up at all. Was bloody RIFA. Removed it, works fine now. don't have VHS tapes but the old guy who donated the VCR also donated a tape of Star Wars the Phantom Menace.

Anyway it plays the tape... audio is just fine, I can hear the movie sound track just fine, but no video !  >:(

I tried using SCART and video composite on two different LCD monitors equipped with these I/O, and every time the same answer : " No sync ", and a black screen, so not happy.

Looked at the schematic, have partial ones, not the main board sadly... but have the one for the rear panel PCB that carries the I/O connectors, and plugs right angle to the mother board.
I see that the video composite signal comes from a chip on this board, and is served to both the RCA jack AND the SCART connector. Apparently SCART has both RGB and composite signals available. I don't know which one the monitors actually use when I ask them to display SCART. Anyway, at least if make some sense that both SCART and composite would not work...

Anyway, I scoped the composite signal on the RCA jack, and to me looks like a I do have my composite signal ?!  So why doesn't it work ?!  :-//

I know squat about video let's be clear.... I simply looked at Google to find diagrams of what it should look like. I have my negative sync pulse, about 5us as it should. Total frame length is about 64µs as measured with the cursors, which is what it should be about. So as far as sync goes, the LCD monitors should be able to detect a signal eh ?!  :-//

My two main worries that might explain the problem (?!), tell me what you think :

- Noise... as you can see from the video clip below and my screenshot, there is lots of noise... but that could just be my probing setup which is more than awful of course, not having a BNC to RCA adapter nor even a coax cable.. so just using my probe in x1 and a little contraption made from recycled RCA jacks. It's too ugly to be showed here, don't want to stoned.

- Looks like there is a HF signal superimposed on everything, whose vertical excursion spans the entire composite signal... looks like faint squiggly lines at the top and bottom of the waveform.  This does not show on wave form diagrams I see on the net.. however I understand there are two combined signals on these things, "luminance" and "chrominance", so maybe what looks like squiggly lines is just one of those two signals and everything is fine . I am so clueless it's painful.

- Voltage levels : 99% of the diagrams I found do NOT indicate voltage levels. Instead they use funny "IRE" units, whatever that means, to give the proportions of the various parts of the signal, but not actual voltages. Proportions look fine on my signal, I find. Video content is about 2+ as high as the sync pulse.
The rare diagrams I found that did indicate voltage levels, showed a 1Vpp excursion, but I get as you can see 2.5Vpp or so !  :scared:

It's so horrible to hear the sound track of Star Wars but not being able to see the video even though I can see it on the scope !!!  |O

Anyone here with working knowledge of composite signals ? I am in Frog land so I guess we are talking SECAM, though from what I see, SECAM / PAL / NTSC have very similar looking wave forms...







Just going back to your original VCR posting, a little snippet of information:

Both NTSC & PAL encode their colour information on the colour subcarrier using "Double sideband supressed carrier" modulation, hence the colour information changes in amplitude similarly to the "baseband"(B & W) video component.

SECAM encodes the colour information using Frequency Modulation, so it appears as a constant amplitude signal in the resultant composite video.

We learnt this, back in the day, but I can't remember ever seeing a SECAM video waveform before, so it looks weird!
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110431 on: January 05, 2022, 02:50:41 pm »
K, fine. Wall of text that means exactly as much to me as what some of us said about VCRs means to Vince. Not all of us are strong with the organic chemistry; from what I could tell of what you were saying, they seemed very similar. If you'd said simply that methyl hydrate was a lot worse, I'd have known that was what you meant.

If you weren't being deliberately obtuse, great. The end result is the same: You didn't communicate what you meant to everybody in your audience.

For my part, I'll remember to ask you next time you say something in chemistry-ese that doesn't 100% make sense to me, even if I think got the gist of it. ;)

Cheers,

mnem
*toddles off to ded*

I wonder if you're doing with things your brain labels as "chemistry" what SWMBO does with things she thinks are labeled "math", turning your head off and going "It's X, I don't understand X". Even when it's something that she needs no prior actual mathematics to get a grip on and I know that she's has the intellectual horsepower to fully grasp it she reacts the same to anything labelled "math". If she didn't perceive it as being "math", she'd have no problem with it.  There was nothing there that I wouldn't expect you to understand, no actual chemistry content, just English.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Vince

  • Super Contributor
  • ***
  • Posts: 4247
  • Country: fr
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110432 on: January 05, 2022, 02:52:24 pm »

[...] but I can't remember ever seeing a SECAM video waveform before, so it looks weird!

My pleasure !  ;D
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110433 on: January 05, 2022, 03:02:48 pm »
Gave the new KiCAD 6 a proper try, very impressed so far.

Have you tried looking up any help in pcbnew? On footprints, or zones, or pads. You might get a nasty surprise.  >:D

Quote
Also gave some thought on the output impedance of the 74HC04. It should be about 70 \$\Omega\$ at 5V Vcc.

That sounds a little high off the top of my head, based on my own previous trawling of datasheets. Be aware that it's uncontrolled, and while one particular brand (and silicon generation) of chip can be quite consistent everything can go out of the window if you change brand or over time they change the silicon.  It's one of those occasions when it's best to specify the part by vendor and vendor part number and not generically.

Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
The following users thanked this post: Vince

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110434 on: January 05, 2022, 03:05:44 pm »
Aww, man... what a letdown. For a moment I thought this vid was about osculation being good for heart murmurs.   >:D

mnem
 :o
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110435 on: January 05, 2022, 03:16:37 pm »
Reminds me of this:

https://www.iflscience.com/editors-blog/56-percent-of-americans-dont-think-we-should-teach-arabic-numerals-in-school/

Gee, it's common knowledge that most Americans are fat due to shitty diet and dumb as a box of rocks due to failing education system. So you have to remind us of that and post this which is like hanging a huge slab of rotten smelly meat on a pole out in open. Hope you're happy and better have these handy. You're gonna need them.

Think I'll stay off the blog today.   

For fucksake dude. As far as I am concerned the fact that Americans are the subject of that study is a pure coincidence. It was meant to illustrate people are stupid, not that Americans are stupid.

It's a fact that a large proportion of studies published, whether in medicine, psychology, education, whatever, are done by American universities. This means that the subjects of those studies tend to be American, also frequently white, relatively well educated, and relatively affluent (i.e. American college students [biased toward male as well]). It's actually a problem as far as validity and reproducibility go - it has caused some nasty surprises in medicine. It also increases the likelihood that if it says something "not nice" about the subjects it's going to per force say it about Americans. If one is also going to get offended by that because one is American, then one has a systematic problem with academic studies.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
The following users thanked this post: mnementh

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110436 on: January 05, 2022, 03:20:53 pm »
K, fine. Wall of text that means exactly as much to me as what some of us said about VCRs means to Vince. Not all of us are strong with the organic chemistry; from what I could tell of what you were saying, they seemed very similar. If you'd said simply that methyl hydrate was a lot worse, I'd have known that was what you meant.

If you weren't being deliberately obtuse, great. The end result is the same: You didn't communicate what you meant to everybody in your audience.

For my part, I'll remember to ask you next time you say something in chemistry-ese that doesn't 100% make sense to me, even if I think got the gist of it. ;)

Cheers,

mnem
*toddles off to ded*
I wonder if you're doing with things your brain labels as "chemistry" what SWMBO does with things she thinks are labeled "math", turning your head off and going "It's X, I don't understand X". Even when it's something that she needs no prior actual mathematics to get a grip on and I know that she's has the intellectual horsepower to fully grasp it she reacts the same to anything labelled "math". If she didn't perceive it as being "math", she'd have no problem with it.  There was nothing there that I wouldn't expect you to understand, no actual chemistry content, just English.
Nope, just plain and simple misunderstanding; which could have been pointed out in a much more positive tone rather than turning it into another unnecessarily personal "mnem is so very, very wrong" diatribe. A single sentence conveying frustration and IRL stress... hardly qualifies as being a "drama queen", IMO.

I promise: I read every word, more than once, and what I took away just wasn't what you intended, plain and simple. :-//

Cheers,

mnem
« Last Edit: January 05, 2022, 04:19:37 pm by mnementh »
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110437 on: January 05, 2022, 03:23:47 pm »
Aww, man... what a letdown. For a moment I thought this vid was about osculation being good for heart murmurs.   >:D

No, it's "Dynamic Osculation". The osculations have to be big and wet. Try again with a Labrador or a Great Dane.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
The following users thanked this post: mnementh

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110438 on: January 05, 2022, 03:28:40 pm »


   Big and wet, you say...?      BWAHAHAHAHAHA!!!

mnem
*just to agitate med*  >:D
« Last Edit: January 05, 2022, 04:20:33 pm by mnementh »
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 

Offline tggzzz

  • Super Contributor
  • ***
  • Posts: 20722
  • Country: gb
  • Numbers, not adjectives
    • Having fun doing more, with less
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110439 on: January 05, 2022, 03:32:49 pm »
Also gave some thought on the output impedance of the 74HC04. It should be about 70 \$\Omega\$ at 5V Vcc.
That opens two possible routes: parallel two gates for ~35 \$\Omega\$ and put 15 \$\Omega\$ in series,
or make it an "equal resistive splitter". For that one, each port should have ~17 \$\Omega\$ in series with it's 50R source impedances.
That fits rather well in the 70R ballpark, so we split off one gate with two 18R in series onto two outputs.
Only downside is you will have to terminate both for impedances to be correct.

If you are doing it to thump a square wave into 50ohms, can I suggest three (74lvc1g* + 143ohms) in parallel. That has a risetime of <300ps.

The 74lvc1G* outputs are pretty much 7ohms. Make sure you decouple them very well, ideally having ground planes separated by prepreg :)

FFI https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg1902941/#msg1902941
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 
The following users thanked this post: Vince, ch_scr

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110440 on: January 05, 2022, 04:09:46 pm »


This came up in the "suggested" list on that vid vk6zgo posted; lots of really interesting enginerdery involved in the new Veedub ID.4 AWD EV drivetrain.

Pull up the big comfy chair and some comfort food; it's pretty engrossing.  :-+   And when you're done with that, here's the ID.4 battery:



mnem
I nerd-sniped myself, so of course I had to pay it forward... >:D
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 
The following users thanked this post: doktor pyta

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3185
  • Country: be
    • Freelance Hardware Engineer
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110441 on: January 05, 2022, 04:19:54 pm »
I've watched a lot of Munroes videos. Good content but after a while his Tesla fanboyism gets a bit old...
 
The following users thanked this post: mnementh

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110442 on: January 05, 2022, 04:25:08 pm »
Huh... he seemed to not shy away from being critical of Tesla's tech in that vid; or rather, did not shy from saying "VW did this way better here..." Yeah, not the same thing. We know that Tesla's drivetrain is not exactly "good for a million miles"; motor failure in the "S" series is a ongoing gripe among owners.

Still a worthwhile watch.

mnem
 :-/O
« Last Edit: January 05, 2022, 04:26:44 pm by mnementh »
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110443 on: January 05, 2022, 04:26:48 pm »
K, fine. Wall of text that means exactly as much to me as what some of us said about VCRs means to Vince. Not all of us are strong with the organic chemistry; from what I could tell of what you were saying, they seemed very similar. If you'd said simply that methyl hydrate was a lot worse, I'd have known that was what you meant.

If you weren't being deliberately obtuse, great. The end result is the same: You didn't communicate what you meant to everybody in your audience.

For my part, I'll remember to ask you next time you say something in chemistry-ese that doesn't 100% make sense to me, even if I think got the gist of it. ;)

Cheers,

mnem
*toddles off to ded*
I wonder if you're doing with things your brain labels as "chemistry" what SWMBO does with things she thinks are labeled "math", turning your head off and going "It's X, I don't understand X". Even when it's something that she needs no prior actual mathematics to get a grip on and I know that she's has the intellectual horsepower to fully grasp it she reacts the same to anything labelled "math". If she didn't perceive it as being "math", she'd have no problem with it.  There was nothing there that I wouldn't expect you to understand, no actual chemistry content, just English.
Nope, just plain and simple misunderstanding; which could have been pointed out in a much more positive tone rather than turning it into another unnecessarily personal "mnem is so very, very wrong" diatribe. A single sentence conveying frustration and IRL stress... hardly qualifies as being a "drama queen", IMO.

I promise: I read every word, more than once, and what I took away just wasn't what you intended, plain and simple. :-//

Cheers,

mnem


Strewth man you're touchy today. Stop trying to read everything as being aimed at belittling you. Trust me, if I want to lay into you it will be obviously and unambiguously written to do so (either that or crafted as the "English insult" so that you think you're being complimented and everybody else is laughing behind your back). Stop inferring malice where none is implied. If I don't actually call you a "fat stupid American fuck" I'm not trying to hide it in the subtext; and before you read that wrong, that's an example, not an intended insult. If I'm aiming a "diatribe" at you, it will look like one.  If I accuse you of being overly dramatic, it's because you chose words like diatribe ("a forceful and bitter verbal attack against someone or something") when there's no "attack", no "forceful" and no "bitter".

My past editors have told me that I'm a good writer, which in the magazine world means "You convey, to the target audience, what needs conveying." not "Oh, we've found the new papa Hemmingway.", so I have some confidence that I can get across in writing what I intend. Now, if every man and his dog was telling me that they forever get the wrong end of the stick when I write something here then I'd take a hard look at the style and content of what I post. But that hasn't happened.

Now, I've spent way too long on composing this carefully so there is no way a reasonable person could read it as containing any attacks, criticisms and other things that the subject could take offence at other than "You're being too sensitive" and "You do over dramatise". If you choose to take this as a "bitter forceful attack" on you then these is nothing else I can do; moreover I'm not going to spend this level of effort each and every time I have something to say that you might choose to treat as the opening shots of a verbal war.

I'm tired of having to treat you with kid gloves, and every time I think you're out of that space where you take everything as an attack and can be talked to without picking every word like it's the one gem in pile of shit, you start again. I don't have the energy to constantly deal with that, and you might just be beginning to see from other people's weary remarks about "the dragon" that I'm not the only person who feels that way.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
The following users thanked this post: xrunner, Vince

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110444 on: January 05, 2022, 04:32:30 pm »
Also gave some thought on the output impedance of the 74HC04. It should be about 70 \$\Omega\$ at 5V Vcc.
That opens two possible routes: parallel two gates for ~35 \$\Omega\$ and put 15 \$\Omega\$ in series,
or make it an "equal resistive splitter". For that one, each port should have ~17 \$\Omega\$ in series with it's 50R source impedances.
That fits rather well in the 70R ballpark, so we split off one gate with two 18R in series onto two outputs.
Only downside is you will have to terminate both for impedances to be correct.

If you are doing it to thump a square wave into 50ohms, can I suggest three (74lvc1g* + 143ohms) in parallel. That has a risetime of <300ps.

The 74lvc1G* outputs are pretty much 7ohms. Make sure you decouple them very well, ideally having ground planes separated by prepreg :)

FFI https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg1902941/#msg1902941

That's very much the setup that I've drafted for the little distribution amplifier that will go in my GPSDO once it is finished and in final form. I did a dry run, paralleling up some LVC gates in DIL packaging on a bit of Veroboard and the results were encouraging as far as my 350MHz scope can show. Also the package stayed nice and cool in 24x7 operation.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110445 on: January 05, 2022, 04:40:05 pm »


This came up in the "suggested" list on that vid vk6zgo posted; lots of really interesting enginerdery involved in the new Veedub ID.4 AWD EV drivetrain.

Pull up the big comfy chair and some comfort food; it's pretty engrossing.  :-+   And when you're done with that, here's the ID.4 battery:



mnem
I nerd-sniped myself, so of course I had to pay it forward... >:D

Beware, I've watched a couple of that Munro chap's videos and he said some things that didn't jibe with what even I know of motors and motor control. I can't recall specifics, but I do recall getting the sense that he's someone who should be taken with a pinch of salt. I've encountered a couple of times that people on here have taken statements of his as definitive when in fact they've been "ex-cathedra" pronouncements that were swiftly taken apart by those with some serious motor control chops and who actually design cutting edge battery systems. You can find the discussions buried somewhere in the interminable electric vehicle threads on here, if you're feeling brave enough.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Specmaster

  • Super Contributor
  • ***
  • Posts: 14483
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110446 on: January 05, 2022, 05:44:13 pm »
Reminds me of this:

https://www.iflscience.com/editors-blog/56-percent-of-americans-dont-think-we-should-teach-arabic-numerals-in-school/

Gee, it's common knowledge that most Americans are fat due to shitty diet and dumb as a box of rocks due to failing education system. So you have to remind us of that and post this which is like hanging a huge slab of rotten smelly meat on a pole out in open. Hope you're happy and better have these handy. You're gonna need them.

Think I'll stay off the blog today.   

For fucksake dude. As far as I am concerned the fact that Americans are the subject of that study is a pure coincidence. It was meant to illustrate people are stupid, not that Americans are stupid.
This is living proof that this thread is just a family (or am I the only one who thinks this way?), by that I mean, all of these silly little throw away bits of chat on here that get taken the wrong way and results in others taking sideswipes at the OP, make threats to stay off the forum etc. Isn't that precisely what happens in most families? In fact, most arguments start over something completely innocent, innocent because the recipient either did not understand the comprehension of the information or it was badly presented or whatever.

Perhaps we should all make 2022 the year that if someone writes something that the reader takes exception to, that we stop and try and fathom it out and if necessary, ask the OP to clarify more so we can hopefully avoid such clashes in the future  :-// :-//
Who let Murphy in?

Brymen-Fluke-HP-Thurlby-Thander-Tek-Extech-Black Star-GW-Avo-Kyoritsu-Amprobe-ITT-Robin-TTi
 
The following users thanked this post: Vince, Ice-Tea, mnementh

Offline AVGresponding

  • Super Contributor
  • ***
  • Posts: 4841
  • Country: england
  • Exploring Rabbit Holes Since The 1970s
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110447 on: January 05, 2022, 06:08:26 pm »
: when the picture turns to B&W... I notice that I can make it go back to colour if I fast forward just a few seconds. Then I fast rewind a few seconds to go back to the part of the movie that was previously B&W and now... oh magic it's in coiour now !  So that means the tape itself is not the problem I guess.... must be the VCR doing something funny.

I am pretty sure it is false triggering on turning the color decoder on when you wiggle it that way. If you look at the color picture you attached, it is evident the colors are wrong and color interferrence can be seen in form of a mesh, also visible on top of the black frame bars.


I don't understand any of what you say, I don't kn,ow my VCR stuff  :(

But do I sense that you agree that the problem might that the tape is not guided and/tensionned properly ? After wigglijg it a bit using Fast forward/rewind, I had no more B&W ruin my viewing for the entire movie !  :D 
So I guess the tape was not properly positioned on the drum, and wiggling it brought it back where it should be.
I guess when in playback mode, it's a bit loose and wanders about. Might also (?) explain another issue I am witnessing : very blurry/fuzzy picture, like it's way out of "focus", say. Also very unstable, it's moving up and down all the time, randomly, but incessantly.

I guess could be worse playing with the mechanical adjustments responsible for positioning and tensioning (is that a new word ? Firefox chokes on it...) the tape ? Don't don't how to do that, need to do some reading...

I did watch a few VCR repair/service videos on " 12votlvids " YT channel. Will watch his VCR vids again to refresh my memory....

The blurry/fuzzy picture is probably due to the limitations of the consumer/home VHS machines, if I remember correctly from the TV programme "Secret Life of Machines" you only got about half the quality of a live TV broadcast from a VHS tape, as only half the information (lines) are recorded, commercial video recorders must have been different.
Also older LCD TV's tend to make standard definition analogue content look even worse, even digital TV looked blocky & crap of the last dumpster find TV I had.



David

This post was "recorded on sticky tap & rust".  :-DD

Easy,----- "The secret Life of Machines" lied!--

Edit:Actually they didn't, you just "got the bull by the horns!"
Even fast forwarding through the first bit, that's about 20 minutes of my life I'll never get back ----AAaaarrrrgggghhh!

Home VCRs recorded all the lines, but the reason for a reduction in quality was mainly that the video bandwidth was reduced due to some other compromises in the design.

I also found that pre-recorded tapes varied quite a lot in picture quality, ---"off air" tapes, much less!

When we first got a VCR, I was watching a football game, (Australian Rules Football, or Cricket on a nice sunny day are good "standards" to go by) so simply recorded some of that, so, whilst the "footy" was on, I could switch back & forth.

The taped version was definitely not as high in resolution, but was quite acceptable.

A few years ago (better part of two decades in fact lol) I was recruited by Ipsos Mori to their TV viewer monitoring scheme.

The guy that came to set the system up had some trouble because the picture jitter on my VCR was so low his detection gear was having trouble telling it from the broadcast picture (good signal quality analogue). It was a Sony (ofc) SLVE something-or-other, good but not top of the range. Late model VCRs were very good, though of course over time the heads and the transport still degrade, iirc I eventually took it out of service because it was folding the top of the picture playing back tapes I'd recorded some time ago, and I had a BluRay player by then (PS3, paid for by the Ipsos Mori scheme...) anyway.
Naturally it helped to use good quality tapes as well, which I did, TDK, Sony, Panasonic etc high grade ones.

I watched a yt vid a few years back on the process of archiving to digital by the likes of broadcasters who sometimes have to recover lost episodes by using VCR recordings from the public, and how they bake the tapes at a low heat for many hours before playing them maybe once or twice before they are deemed phkt.
nuqDaq yuch Dapol?
Addiction count: Agilent-AVO-BlackStar-Brymen-Chauvin Arnoux-Fluke-GenRad-Hameg-HP-Keithley-IsoTech-Mastech-Megger-Metrix-Micronta-Racal-RFL-Siglent-Solartron-Tektronix-Thurlby-Time Electronics-TTi-UniT
 

Offline Cerebus

  • Super Contributor
  • ***
  • Posts: 10576
  • Country: gb
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110448 on: January 05, 2022, 06:42:18 pm »
I watched a yt vid a few years back on the process of archiving to digital by the likes of broadcasters who sometimes have to recover lost episodes by using VCR recordings from the public, and how they bake the tapes at a low heat for many hours before playing them maybe once or twice before they are deemed phkt.[/color][/size][/b]

Another trick I've seen for restoring magnetic tape is to hold it in a constant low vacuum* for a period of time to extract moisture and other volatiles without introducing any extra heat into the equation.


*In the strange world of vacuum terminology where 'high vacuum' means a very low reading on a pressure gauge and 'low vacuum' means a relatively high reading on a pressure gauge.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline mnementh

  • Super Contributor
  • ***
  • Posts: 17541
  • Country: us
  • *Hiding in the Dwagon-Cave*
Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #110449 on: January 05, 2022, 06:43:08 pm »
Strewth man you're touchy today. Stop trying to read everything as being aimed at belittling you. Trust me, if I want to lay into you it will be obviously and unambiguously written to do so (either that or crafted as the "English insult" so that you think you're being complimented and everybody else is laughing behind your back). Stop inferring malice where none is implied. If I don't actually call you a "fat stupid American fuck" I'm not trying to hide it in the subtext; and before you read that wrong, that's an example, not an intended insult. If I'm aiming a "diatribe" at you, it will look like one.  If I accuse you of being overly dramatic, it's because you chose words like diatribe ("a forceful and bitter verbal attack against someone or something") when there's no "attack", no "forceful" and no "bitter".

My past editors have told me that I'm a good writer, which in the magazine world means "You convey, to the target audience, what needs conveying." not "Oh, we've found the new papa Hemmingway.", so I have some confidence that I can get across in writing what I intend. Now, if every man and his dog was telling me that they forever get the wrong end of the stick when I write something here then I'd take a hard look at the style and content of what I post. But that hasn't happened.

Now, I've spent way too long on composing this carefully so there is no way a reasonable person could read it as containing any attacks, criticisms and other things that the subject could take offence at other than "You're being too sensitive" and "You do over dramatise". If you choose to take this as a "bitter forceful attack" on you then these is nothing else I can do; moreover I'm not going to spend this level of effort each and every time I have something to say that you might choose to treat as the opening shots of a verbal war.

I'm tired of having to treat you with kid gloves, and every time I think you're out of that space where you take everything as an attack and can be talked to without picking every word like it's the one gem in pile of shit, you start again. I don't have the energy to constantly deal with that, and you might just be beginning to see from other people's weary remarks about "the dragon" that I'm not the only person who feels that way.
Oi...

That's it; The bar is closed, you're cut off. ;)

When you came looking for a argument with the whole "Aww... this isn't that dangerous..." thing, I figured okay... I'm a good friend, I'll oblige and bite. It were a good one too, until you turned it personal. Evidently you needed it so what the Hell; I was feeling game and my hide is thick.
But I have to draw the line at 2 days... Sorry, as much as I sometimes love to indulge in a good old knock-down drag-out, I really have too much going on IRL ATM. I love you man, but I just can't right now. I'm sorry.

Cheers,

mnem
don't make me bring out the ...
alt-codes work here:  alt-0128 = €  alt-156 = £  alt-0216 = Ø  alt-225 = ß  alt-230 = µ  alt-234 = Ω  alt-236 = ∞  alt-248 = °
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf