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Test Equipment Anonymous (TEA) group therapy thread

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mansaxel:

--- Quote from: cyclin_al on January 23, 2022, 04:22:53 am ---
However, we also have another scenario called "split receptacle" to provide MOAR POWER ... !  (In a normal circuit, the total circuit can only supply 15A at 120V.)

--- End quote ---

And here, since most every feeder from the power company is 3-phase (I've seen flats/condos/apartments/Wohnungen in recent times with 1-phase supply, but that usually was in houses where there are three apartments to each staircase level, splitting the riser nicely), you always have to think about the possibility of having 405VAC between two phase conductors. And it is legal to pull them in same conduit, at least if all three phases are present, and the target is an outlet or junction box for a three-phase consumer. Or a two-phase one. Such things exist; a common example might be an induction stovetop.  It is then fed by 2 phase conductors, and a Neutral, and of course PE. In the more modern ones, I think they SMPS the 400V between the phases into Useful Current and then the resultant current in the neutral is 0; if you were to take the current as two 230V loads against neutral the neutral current of course is (and this is a simplified formula that works in just the pathological case of one phase completely unused; the more general formula is a bit more involved)

sqrt(2) * (currentphase1 + currentphase2)/2)

for 2x 10A giving 14,1 A neutral current.  A tricky trap, that. Solution is really easy; just add a consumer to third leg.   The problem grows tentacles and gets really out of hand if you have mains distortion, because not even with nominally balanced consumers the overtones are going to balance, heating the neutral badly. There has been some spectacular fires resulting from that.

I have a three-phase feeder to my stovetop / oven place in the kitchen, which is IIRC 5g1,5mm2, so I'll have to be careful. Most ovens are single-phase, and the induction tops are two-phase. I'd preferred them to be three-phase both; much easier load-balancing.

Vince:

--- Quote from: BU508A on January 23, 2022, 01:21:07 pm ---In Germany there is this TV show "Bares für Rares (cash for rares)" where someone offered a Tektronix 541A.
Apart from the expert, nobody really knew what to do with the device. In the end, it was sold for 100 euros.

--- End quote ---

Wow that's cool ! The Tek is the star of the show (a segment of it anyway) and you can see it really well in the picture !  :D

I think it would be worth contacting VintageTek museum in the US so they can add it to their database ! They keep track of the old Tek scopes that appeared in moves and shows !  :D

Look here :

https://vintagetek.org/tektronix-in-movies-shows/

BU508A:

--- Quote from: Vince on January 23, 2022, 01:32:55 pm ---
--- Quote from: BU508A on January 23, 2022, 01:21:07 pm ---In Germany there is this TV show "Bares für Rares (cash for rares)" where someone offered a Tektronix 541A.
Apart from the expert, nobody really knew what to do with the device. In the end, it was sold for 100 euros.

--- End quote ---

Wow that's cool ! The Tek is the star of the show (a segment of it anyway) and you can see it really well in the picture !  :D

I think it would be worth contacting VintageTek museum in the US so they can add it to their database ! They keep track of the old Tek scopes that appeared in moves and shows !  :D

Look here :

https://vintagetek.org/tektronix-in-movies-shows/

--- End quote ---

Done.  :-+

Vince:

--- Quote from: Vince on January 23, 2022, 01:10:47 pm ---VARTA Battery :

I am sad to say that the poor battery did not survive the night.

IIRC I started discharging it at 2AM last night. I just woke up, 12H45, so about 10+ hours, immediately checked on the battery.... only to find voltage was down to.... 7 V ? No... well below that.... which is still a massive understatement.... voltage was down to....  0.8V !!  :scared:

Rob I am so sorry, I failed to protect this battery from under voltage.... I am a failure....

That said... even at 0.8V believe it or not, it was still spitting out a sizable current, 1mA !!  :o

After 5 minutes or so, battery recovered a bit and unloaded voltage went up to 2.5V.... which from memory was also the voltage it read after its 30 years of storage when I dug it out the other day !
So I guess this battery "likes" this particular voltage...  :-//

So what to do now...

First I would like to not over dramatize the fact that I let it go flat.... because it had already been flat for 30 years, so I probably didn't do any more damage than had already been done, eh ?

Also, the fact it was still putting out 1mA at only 0.8V means, to me at least, that it's a warrior, it wants to live...

So I think I will charge it again, using Wilson. Slow C/10 again.

Then will do another discharge cycle, but this time I will conduct the experiment during the day, so that I can keep an eye on it regularly, from beginning to end, and will take note of precise start time, and time stamp for every voltage and current check I do.

Would be easier if I could do it automagically with a GPIB setup and some clever S/W on a computer... but alas the lab is nowhere near as sophisticated for now ! It's my plan for it be, though...

Also, since I have plenty of real estate on the bread board, I could add a comparator chip and a little miniature relay to automatically disconnect the battery when it reaches a certain voltage threshold. That would be neat.

The saga continues....

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Oh, looks like the battery is recovering...  it's not stuck at 2.5 V no. Been disconnected for a couple hours now, and voltage is still climbing, now up to 4V.

hmmm.... maybe after a few charging cycles it will recover some health.... will keep at it !  8)

I will wait for voltage to stabilize before charging it again... don't want to brutalize it !  ;D

TERRA Operative:

--- Quote from: Vince on January 23, 2022, 12:38:16 pm ---Ah great !  :-+

Had a similar moment when I fixed my 544A I remember... I had it fixed,working... then I put it back together and it failed to boot !  :scared:

After pulling my hair and being close to wanting to throw it in the trash... I eventually found the problem !
See that little " bus " board on the side of the scope, that connects the bottom and top boards together, to supply power and data lines ???
Well... turns out it is NOT keyed, it can be rotated 180° and it will still snap into place just fine !  :scared:

So yeah, I had put it back the wrong way around... luckily it did not cause any damage and the scope has been just fine for 5 years now ! :-+

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Yep, I know exactly what you are talking about, and I won't say how I know, multiple times...........  :-DD |O

In related news, I realised I have enough TDS754D parts to essentially completely convert a TDS744A into the TDS754D (By swapping boards etc), so that I'll do. Get me more cash for more test gear when I sell it. :D
So I'll have on hand 3x TDS754D's, a TDS620B and my current crown jewel, a TDS784C.
I have most of the parts to convert the TDS620B into a TDS644A too, except the front panel and CRT (Got two CRT's but with faulty LCD shutter panels), so I'll leave that one for now.

In the words of a certain green anti-hero.....