Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 16897725 times)

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Offline McBryce

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61100 on: June 16, 2020, 05:21:18 pm »
Ok, but why did they leave the device floating with no ground?

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Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61101 on: June 16, 2020, 05:46:37 pm »
Ok, but why did they leave the device floating with no ground?

McBryce.
Is there a separate gronding terminal on it? Then I would suppose that they did this to avoid the dreaded ground loops. But as it is a consumer device, the user can't be trusted to connect an external ground correctly. So it would be legal only if it were in fact a class II device and the (external) ground comes in use on the secondary side only.
 

Offline Saskia

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61102 on: June 16, 2020, 05:50:47 pm »
I second that ...
 

Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61103 on: June 16, 2020, 06:12:11 pm »
I really have to vent here now.  :blah:
That crappy and totally useless automatic translation on Ebay drives me crazy! It goaded me into looking up if there is really a manufacturer of magnetometers which I did not know until I realized that 'F.W.Glocke' is a no-brainer translation of F.W.Bell.
Every time I look at crimping tools on Ebay is getting slightly offensive and very personal as it wants to talk about death with me. 'Die' and 'dies' jump at you tranlated variously as 'stirb!' , 'sterben', 'gestorben' etc.
And the same happens with threadcutting tools. 'tippen und sterben' might put someone off betting, but as a translation for tap and die, it is useless. And they use colloquial language instead of proper English, so that all those woodworking tools become a 'Flugzeug' from being called 'plane', but no airplane.
They don't even stop at RF adaptors. A 'Kings T connector' was listed as 'koenigliches T-shirt verbunden'. :wtf:

And you can't even turn this shit off. Totally annoying. How is it the other way round?
 
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61104 on: June 16, 2020, 06:15:04 pm »
Ok, but why did they leave the device floating with no ground?

McBryce.
Is there a separate gronding terminal on it? Then I would suppose that they did this to avoid the dreaded ground loops. But as it is a consumer device, the user can't be trusted to connect an external ground correctly. So it would be legal only if it were in fact a class II device and the (external) ground comes in use on the secondary side only.

Not sure that's a good excuse... back in the day I modded many classic receivers & power amplifiers with a grounded cord to properly ground the metal shell. Nearly always resulted in perceptibly reduced noise floor, as long as I made sure the only ground to attached components was via the patch cables. On my own gear, I did my best to ensure that those components' chassis were connected to the RCA jack grounds directly or if not possible, by 10K resistor/1uF ceramic cap; this at the recommendation of old man Basche, the guy who got me started in electronics. This practice has served me well over 4 decades; I see no reason to stop now. :-//

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Offline bd139

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Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61106 on: June 16, 2020, 06:29:35 pm »
Not really TEA, but I've just been given a Denon AVC X8500H to repair. It has the biggest transformer I have ever seen inside a commercial device.

McBryce.

(for info, the primary side of the PSU shorted for some reason, haven't found out why just yet).

What I've never understood: in such high priced stuff, why don't they use toroidal transformers? Always wondered about that.

Higher inrush current, more expensive, no real advantage...

Why do you think that? All other things being equal the inrush current (unloaded) is going to be determined by the amount of flux to be generated, not by its shape. I'm quite prepared to be educated...
The high inrush current of toroidal trandformers is not caused by the shape and there are some other transformers to which this applies too. The point is that the wide commercial availability of premade toroidal transformers made people, which do not know much about transformers, notice this fact.
It typically occurs when someone replaces an E-kernel transformer with a toroid of similar ratings, which then blows the fuse or trips the breaker when switching on.
The cause of the high inrush current is that the core of the toroidals is made up of high permeability alloys instead of iron. Also, an air gap is absent.
Ánother factor might be that their quiescent current is lower, so that the inrush appears even higher in relation to it.
If you would build a E-type transformer from the same materials, the effect would be there, but less that in a toroid, because there would still be an air gap. The other transformers which are using the same materials are compact transformers with a very flat form factor. The inrush current applies to them as well.
(all above applies to low voltage line transformers)
« Last Edit: June 16, 2020, 06:31:26 pm by Neomys Sapiens »
 
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Offline mansaxel

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61107 on: June 16, 2020, 06:41:05 pm »
Just spent the entire morning whinging about a misconfigured JIRA instance.

Is there any other kind?  :)

That's a depressingly good point  :-DD

This one marks the ticket as completed immediately when you create it ?!?!?  :palm:

As I'm often on the receiving end of tickets, I fail to see how that particular behaviour is a failure.

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61108 on: June 16, 2020, 06:46:11 pm »
Ahh I'm only creating 'em  :-DD
 

Offline AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61109 on: June 16, 2020, 07:03:18 pm »
The only real, non-audiophool reason for having a donut instead of house brick is size and weight.

And stray field. The difference in stray magnetic field between a toroid and other topologies is quite remarkable. The ratio is about 8:1, more if you slap a flux band around the outside of the toroid. If you've low level signals inside your box (e.g. signals from pickups for pressed media made from the secretions of the Lac Beatle) a toroid makes your life much easier in a bit of integrated audio gear.

Where I've been surprised to not see toroidal transformers in use is in instrumentation. I'd have thought that the gains from low field emissions would have more than offset the additional cost of toroids for instrumentation that has sensitive, high impedance inputs. True, it's easier to add an electrostatic screen for suppressing common mode interference to a classic transformer but it's not impossible on a toroidal, just a bit more awkward.

You just answered your own question!   :-DD

I've only ever seen unscreened EI trannys is the most heinously shite-tastic audio gear. Half decent stuff always has well screened ones, like test gear...   :popcorn:
0

Oh, the Keysight test leads turned up today, pretty fast I thought. The bag is a factory heat-sealed ziplock, very nice, and clearly from a larger box containing well arranged active componentry...
Interestingly the leads are rated 1000V 15A, but all the attachments are only rated 300V 3A.

The fine tip probe attachments look like something out of an acupuncturists, or maybe something Saskia would shoot at me for scooping them ahead of her...   :scared:
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Offline Saskia

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61110 on: June 16, 2020, 07:06:43 pm »
grrr. that was his last pair he said.
 
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Offline AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61111 on: June 16, 2020, 07:16:14 pm »
grrr. that was his last pair he said.

*changes identity and moves house*
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Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61112 on: June 16, 2020, 07:27:27 pm »
The only real, non-audiophool reason for having a donut instead of house brick is size and weight.

And stray field. The difference in stray magnetic field between a toroid and other topologies is quite remarkable. The ratio is about 8:1, more if you slap a flux band around the outside of the toroid. If you've low level signals inside your box (e.g. signals from pickups for pressed media made from the secretions of the Lac Beatle) a toroid makes your life much easier in a bit of integrated audio gear.

Where I've been surprised to not see toroidal transformers in use is in instrumentation. I'd have thought that the gains from low field emissions would have more than offset the additional cost of toroids for instrumentation that has sensitive, high impedance inputs. True, it's easier to add an electrostatic screen for suppressing common mode interference to a classic transformer but it's not impossible on a toroidal, just a bit more awkward.

You just answered your own question!   :-DD


Yeah, but it's just the same level of difficulty as winding a toroid versus winding a bobbin.

Quote

The fine tip probe attachments look like something out of an acupuncturists, or maybe something Saskia would shoot at me for scooping them ahead of her...   :scared:[/color][/size][/b]

Those are really nice when trying to poke about smd bits or picking up a signal on a plug-in breadboard just between the insulation of jump wires and where it goes into the hole.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61113 on: June 16, 2020, 07:38:03 pm »
BBC Radio4 currently broadcasting an investigation into the 5G bioshield scam. Some of the people behind it are hilariously wacko.
Apparently the highest frequency in the universe is "love". I would argue it's actually retards, there seem to be more of those about than anything else...

Anyway, to business, I have some plastic. Not the sort that some here like to threaten to use in 50 gram quantities, but Lexan (yes I know it's a trade name, this is afaik genuine) offcuts.
Our maintenance joiners are currently flying round every public facing site putting Lexan shields up, and so there are offcuts...

I have currently only 6 310mmx140mmx8mm with notched corners, but I expect there'll be more. Knee alert.


If anyone wants any, it's yours for the cost of postage, which probably means only the UK is a practical destination. PM me if you're interested.
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Online tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61114 on: June 16, 2020, 07:47:20 pm »
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".
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Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61115 on: June 16, 2020, 07:58:05 pm »
grrr. that was his last pair he said.

*changes identity and moves house*

 :-DD Smart move.  :-DD
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61116 on: June 16, 2020, 08:06:27 pm »
 

Offline AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61117 on: June 16, 2020, 08:13:11 pm »
Dammit, I've had this on my watch list for days and keep forgetting to post a link. One for the baby scope connoisseurs:
https://www.ebay.co.uk/itm/Philips-PM-3010-Oscilloscope-0-to-5-MHz-Listing-Updated-12-06-20-New-Photos/324193019277

Ba-by scope doo doo do do do doo

Also, this pricing is nucking futs, from a seller that's well known for high prices and poor storage conditions:
https://www.ebay.co.uk/itm/Vintage-Philips-QE08-200H-Vacuum-Tube-Valve-GD1/324199054442


And finally, a seller messaged me to say the item I was bidding on just wasn't attracting enough bids, so he sold it to Cash Converters (it's a brand of pawn shop in the UK).
The item? A PS4 game, used, Elite Legendary Edition. My guess is he got less from them than my maiden bid (assuming he was telling the truth; if it pops up again under his seller name, I might just message him back...), which kind of reinforces a point I was making in an earlier post.   :palm:
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Offline 0culus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61118 on: June 16, 2020, 08:16:01 pm »
RE the tube: I see a lot of that, selling high power RF tubes for crazy money. I'd wager very few people have the equipment needed to test such a tube, and I'd want it tested before plunking that much down. My local surplus/junk store has a huge collection of tubes that came in one lot from a store that went belly up. They (as far as I know) still have this neat Eimac radar tube with green uranium glass in the base. The proprietor looked in his tube catalog (which is like, old...from when they were new) and decided he wanted over $1000 for it. I told him to take a hike.  :palm:
« Last Edit: June 16, 2020, 08:17:43 pm by 0culus »
 

Offline AVGresponding

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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61120 on: June 16, 2020, 08:37:19 pm »
50 ohm input. Possible GR-874 by the looks.
 

Offline AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61121 on: June 16, 2020, 09:00:26 pm »
And the 5-pin probe power sockets?
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61122 on: June 16, 2020, 09:03:09 pm »
Don't need them unless it's an active probe :)
 

Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61123 on: June 16, 2020, 09:03:19 pm »
Yep, those are GR connectors which I am beginning to hate and the last time it was calibrated was 1985.  :o
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Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #61124 on: June 16, 2020, 09:07:41 pm »

Those are really nice when trying to poke about smd bits or picking up a signal on a plug-in breadboard just between the insulation of jump wires and where it goes into the hole.
They do not work particularely well IMHO. Their utility is limited by the fact that they have to be stuck onto the standard probes. They can give you some reach, but for SMD work, it is as awkward as dancing on stilts.
For the combination of long reach AND a fine point, I think that the extensible ones from the big Pomona kit are unsurpassed, as you can adjust them to the length that is needed.
Another thing that I do not understand with this kit is why they provide two of the fine type hooks and only one of the type which is more suited to general use. It would make more sense to me if they integrated it with the missing elements of their U1161A kit.

The last probes I bought were a pair from Mueller, because for a short time they were bundled with the KT-MS001 accessory kit (but lacking all others), which contains some interesting items. Especially the thing that can be shoved in-between a stack of batteries did raise my curiosity. The probes themselves are ok but not special. Can't recall whether it was at RS or Digikey.

@Saskia: if you are short of probes, treat yourself to a set of Fluke TL175E (not TL175!) Twist-guard. They are very fine general use probes and the E version comes with threaded 4mm adaptors.
Which part did you like most about that kit? I might find some parts of it except the probes/leads.
If you did think about fine-pitch, read above why they are nogo. The assembly with the stuck-on extensions becomes too long for the required precision.
In that case, would you like to get a pair of those:
https://www.eevblog.com/forum/testgear/useful-adaptor-techniques/msg1223935/#msg1223935
???
I still have some of the sockets left, but you would have to wait until I can order the necessary SKS components (2mm cable jacks) and the 0.25mm² (or similar, but 0.5mm² should be maximum) fine stranded silicone leads. And I would not want to foist the chinese wire on you should be Staeubli.
Shrouded/unshrouded 4mm as per your choice. I also made some of those as extensions with a length of around 10cm, which can be connected to any 4mm leads. Some needles are in spare too, but not all shapes. Contrary to the SKS micro probes with their far too weak springs, they penetrate a solder mask easily and won't slip from a small contact area.
(Available from the ShrewWorks exclusively!)
 


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