Test Equipment Anonymous (TEA) group therapy thread

[25 CPS]

The three ringed circus at the electron floggery is going full blast this morning.

Management's on the warpath.  Some quality stuff went right into the bin in the name of cleaning the place up.  I'm not sure yet if I'll be able to rescue anything.  Then there's the whole high school confidential thing going on.  There's the co-worker who doesn't have an indoor voice who speaks every thought as it crosses his mind blasting at a million decibels.  I can't even think straight.  One of the co-workers just texted me saying "It sucks being here".  I looked over and said I was thinking the same thing.

I miss working from home out of my own workshop instead of at the employer's.

[Specmaster]

13A fuses in the plugtops will see you long dead and are not safe at all they are a throwback solution to a ring main problem.

Which is complete nonsense. They are safe. In fact they are defence in depth. For faults downstream of the plug, if there's a fault with the plug top fuse, the central breaker will catch it, if there's a fault with the central breaker, the plug top fuse will catch it. If your single breaker fails, what's protecting you? Oh yeah, nothing but the smouldering wiring.

Moreover, they allow appliances to be fused at less than the breaker rating. Commonly available plug top fuses go down to 3A (1A is available), at which fault current the central breaker will just sit there and happily continue supplying current, feeding the fault if there wasn't a plug top fuse.

100% this all day.

[Kosmic]

Hooo Boy, I snipped a big one this time (35kg/77lbs) and it's a Fluke! Please remember me to never set an auction listing scheduled to end a midnight on a holiday.

Since my bodge is holding up I did some tesst with my newly acquired Tenma 72-2995.





Nice to be able to generate a AC signal up to 1000V 


It does amps too! 


Overall it look like the calibrator is spot on.

If someone need a 4.5 digits (maybe 5.5digits) multimeter calibrated, let me know 

[Specmaster]

So which hole is the left hole on these sockets?

McBryce.

That just highlights that your system is flawed 

[mnementh]

Cerebus -

I remember you talking aboot looking for some sort of tray to use for populating PCBs; something with a lip to keep flyaways captive. Yesterday I picked this up from the Thrift; it looks like just the kind of thing you were asking for. I'm guessing it is some sort of silicone baking sheet for ummm... I dunno what...?

Dimensions are 150mm x 150mm inside; lip is 10mm high to the inside surface. Bottom measures 2mm thick so marginally safe to solder right on it; or you could just put your PCB on a MetCal potholder or somesuch for a little extra safety.

No idea what they'd call it on your side of the pond; hopefully not too frightfully expensive.

mnem
*solder-ily*

[Specmaster]

@Kosmic, that is pretty good, well done, you cannot complain really about being 100mV out at 100Vac 

[mnementh]

The three ringed circus at the electron floggery is going full blast this morning.

Management's on the warpath.  Some quality stuff went right into the bin in the name of cleaning the place up.  I'm not sure yet if I'll be able to rescue anything.  Then there's the whole high school confidential thing going on.  There's the co-worker who doesn't have an indoor voice who speaks every thought as it crosses his mind blasting at a million decibels.  I can't even think straight.  One of the co-workers just texted me saying "It sucks being here".  I looked over and said I was thinking the same thing.

I miss working from home out of my own workshop instead of at the employer's.

So, what next...? REBRANDING...?

mnem
Hope you get to do some dumpster diving, BTW.

[med6753]

Hooo Boy, I snipped a big one this time (35kg/77lbs) and it's a Fluke! Please remember me to never set an auction listing scheduled to end a midnight on a holiday.

Since my bodge is holding up I did some tesst with my newly acquired Tenma 72-2995.





Nice to be able to generate a AC signal up to 1000V 


It does amps too! 


Overall it look like the calibrator is spot on.

If someone need a 4.5 digits (maybe 5.5digits) multimeter calibrated, let me know 

It's too bad you are across the border of I WOULD be sending you all my stuff to be calibrated.    Nice score and I am blue with envy.   

[shakalnokturn]

So which hole is the left hole on these sockets?

McBryce.

Sorry that's a for Germany.... The good thing is that it should force you into testing before touching or better still cutting the supply, then testing before touching.
I actually quite like Schuko on multiple sockets, it's a shame the French socket isn't also compatible with the Schuko plug. (At least not the ones I've used.)

[shakalnokturn]

@Kosmic, that is pretty good, well done, you cannot complain really about being 100mV out at 100Vac 

Can't he? But who's out? The Fluke or the Tenma? 

[nfmax]

Page 4060. There is a device but I don't have it ... 

I have a few stock in the Drawers. Used one a few months back as a timebase to pulse a 434MHz radio module on every 2 hours 13 minutes, to tell me if my sewage tank is full or not (currently it is). This replaced a PIC micro based design which was much more complicated - it had to be because of the radio modem it was using. Only problem at the moment (apart from the full tank) is that I haven't got round to updating the software on the receiving side, so I have to manually decode a hex dump. Which seems appropraite

[Kosmic]

@Kosmic, that is pretty good, well done, you cannot complain really about being 100mV out at 100Vac 

Can't he? But who's out? The Fluke or the Tenma? 

None of them, or both it's not clear

The Tenma is rated 0.6% + 40 counts on the 1000V AC range. It's reading 0.11% low on the picture. Which is pretty good I would say.

On 10VDC the 5101b is around 66ppm away from my local 10V ref.

[Cerebus]

Cerebus -

I remember you talking aboot looking for some sort of tray to use for populating PCBs; something with a lip to keep flyaways captive. Yesterday I picked this up from the Thrift; it looks like just the kind of thing you were asking for. I'm guessing it is some sort of silicone baking sheet for ummm... I dunno what...?

Dimensions are 150mm x 150mm inside; lip is 10mm high to the inside surface. Bottom measures 2mm thick so marginally safe to solder right on it; or you could just put your PCB on a MetCal potholder or somesuch for a little extra safety.

No idea what they'd call it on your side of the pond; hopefully not too frightfully expensive.

mnem
*solder-ily*

That looks like the silicone version of a swiss roll tray (which has a fancier nom gastronomique that I can't remember offhand). Might be a winner.

[Cerebus]

@Kosmic, that is pretty good, well done, you cannot complain really about being 100mV out at 100Vac 

[Fx: Looks aghast.] But that's 1000 ppm! Think of all the little unemployed ppms!

[Cerebus]

So, what next...? REBRANDING...?

And a custom company logo carpet.

[Kosmic]

So the manual mention testing TP5, TP7 and TP10 for signal. Initially no waveforms were present on those test points. But after poking around with the oscilloscope probe on TP5 I realized that the whole thing started working when a 10Mohm load was bridging TP5 to ground.


I think U30 (NAND Gate) is damage and need to be changed. I don't fully understand why the 10Mohm load to ground make a difference. Increase voltage on the open collector output of U30 ? It also look like the optocouplers U32 and U38 were changed in the 90s.


So I will replace U30 but in the meanwhile I did a quick bodge to try to test the instrument.

More likely U32 has gone low gain / transfer ratio and needs that tiny bit more curent to drive it on.

No.
As the output of the NAND gate switches between -20V and -15V / OC, the 15M to GND (0V) always takes current away from the LED. So IMO it's rather a compensation for increased output leakage of the NAND gate.

Anyway, the usage of optocouplers is interesting here. IIRC, my unit doesn't have any optocouplers at all, all isolation is done by these inductive couplers. In the early years of optocouplers, the inductive couplers were way more reliable.

That was also my conclusion. Thank you for confirming.

Is it possible these problems are a secondary effect of the mixing of boards from late model donor to an early model unit...? Possibly "retrofit mods" that would be part of a factory service procedure that never happened because the boards were changed by someone who didn't know better...?

mnem

Will see. I will be replacing U30 and removing the 15Mohm resistor.

[Cerebus]

Page 4060. There is a device but I don't have it ... 

I have a few stock in the Drawers. Used one a few months back as a timebase to pulse a 434MHz radio module on every 2 hours 13 minutes, to tell me if my sewage tank is full or not (currently it is). This replaced a PIC micro based design which was much more complicated - it had to be because of the radio modem it was using. Only problem at the moment (apart from the full tank) is that I haven't got round to updating the software on the receiving side, so I have to manually decode a hex dump. Which seems appropraite

So we can legitimately tell you that you're full of shit? Well, at least for a while... 

[beanflying]

Hooo Boy, I snipped a big one this time (35kg/77lbs) and it's a Fluke! Please remember me to never set an auction listing scheduled to end a midnight on a holiday.

spippity

So I will replace U30 but in the meanwhile I did a quick bodge to try to test the instrument.

I soldered a 15Mohm resistor between TP5 and ground 

Nice Score  Got a fairly dead one sitting on the rack awaiting some time too. Epic 9 hour pickup run to get it last year just as the Plague was starting.

First Road trip in a year today too few hundred km's to go talk to a new Waterjet Cutter as my nearest one has gotten very sub par. 

[med6753]

I guess I can't complain too much. The AD584 after 45 minute warm up. It does drift but seems to settle. Documented on the ref at 9.99691V @ 21 C. Currently 26C in here. About 10 minutes later it drifted to 9.99693V

[mansaxel]

If on the other hand as others have indicated there no legal requirements for which pin the Hot and Neutral wires are terminated at, then that is a recipe for problems.

Why?

I believe that there must be some standard that electricians have to conform to and that the connections of sockets are clearly defined as to what each is supposed to connected to, so that anything that demands a ground connection for safety can only be connected one way when the plug is plugged in, so that the switch on the equipment and any fuse in the equipment is in the Hot or Live line so that in the even of a problem, the fuse isolates the incoming supply to prevent the metal work on the equipment remaining connected to the Live and still present a dangerous situation.

I do not follow.
To me, if you have a system that is dangerously less secure if phase and neutral are flipped, then that system is faulty and needs to be fixed. If there is a difference, but the security level with the polarity switched still is high enough to fullfill the requirements in law/other rules, then there is no actual problem. (Do note that we are discussing the system safety in normal operation, not split open on the bench.)

The cases you put forward, are dealt with by the PE conductor and/or the RCB, and it is therefore important that ground mates first, and that it breaks last. Such details are catered for in most well designed plugs and sockets.   It is also obvious and fulfilled by all plug/socket systems we've discussed that PE must be unambigious.

Regardless of that case,  since you can't safely rule out two different cases,

• Isolating centre tapped transformer or Delta supply
• flipped polarity

...any safe equipment must deal with full mains potential on both conductors of the supply in a way that's no less secure than the "intended orientation".

Issue is moot, and insisting is pointless. IMNSHO.

[mansaxel]

You won't find a mains cord of less than 0.75mm² and that's rare except for double insulated items on C7 connectors. Anything on a C13 will have 1.5mm² conductors or larger.

My Marconi VTVM came with perhaps a 3x 0,34mm². I distinctly remember a lot of small lighting instruments sourced from the UK that came with 3x 0,5mm² cords. But that's some time ago.

[Kosmic]

Hooo Boy, I snipped a big one this time (35kg/77lbs) and it's a Fluke! Please remember me to never set an auction listing scheduled to end a midnight on a holiday.

If someone need a 4.5 digits (maybe 5.5digits) multimeter calibrated, let me know 

It's too bad you are across the border of I WOULD be sending you all my stuff to be calibrated.    Nice score and I am blue with envy.   

If the border reopen one day, we could meet half way.

Before covid I was regularly going in Vermont to buy some stuff or get the packages delivered for me in a PO box.

[Robert763]

So the manual mention testing TP5, TP7 and TP10 for signal. Initially no waveforms were present on those test points. But after poking around with the oscilloscope probe on TP5 I realized that the whole thing started working when a 10Mohm load was bridging TP5 to ground.


I think U30 (NAND Gate) is damage and need to be changed. I don't fully understand why the 10Mohm load to ground make a difference. Increase voltage on the open collector output of U30 ? It also look like the optocouplers U32 and U38 were changed in the 90s.


So I will replace U30 but in the meanwhile I did a quick bodge to try to test the instrument.

I soldered a 15Mohm resistor between TP5 and ground 

More likely U32 has gone low gain / transfer ratio and needs that tiny bit more curent to drive it on.

No.
As the output of the NAND gate switches between -20V and -15V / OC, the 15M to GND (0V) always takes current away from the LED. So IMO it's rather a compensation for increased output leakage of the NAND gate.

Anyway, the usage of optocouplers is interesting here. IIRC, my unit doesn't have any optocouplers at all, all isolation is done by these inductive couplers. In the early years of optocouplers, the inductive couplers were way more reliable.

Ahh not enough of the circuit visible to see the power connections for the gate. I must admit I didn't catch the - in front of the 15V. Such an odd arrangement I made an assumption.
What device is the logic gate?
Adding your resistr does of course reverse bias the LED, less leakage current form the gate, but still not good. I'd channge both optocouplers and the gate package(s). Early optos are not the most reliable devices.
 Check the decoupling round there too.

[med6753]

Hooo Boy, I snipped a big one this time (35kg/77lbs) and it's a Fluke! Please remember me to never set an auction listing scheduled to end a midnight on a holiday.

If someone need a 4.5 digits (maybe 5.5digits) multimeter calibrated, let me know 

It's too bad you are across the border of I WOULD be sending you all my stuff to be calibrated.    Nice score and I am blue with envy.   

If the border reopen one day, we could meet half way.

Before covid I was regularly going in Vermont to buy some stuff or get the packages delivered for me in a PO box.

Sounds like a plan. And I would hand just one (big) instrument. The 3456A. I'm pretty sure it's within tolerance but it would be nice to know for sure especially since it's my bench reference. 

[mnementh]

...any safe equipment must deal with full mains potential on both conductors of the supply in a way that's no less secure than the "intended orientation".

Issue is moot, and insisting is pointless. IMNSHO.

Mmmokay... how do you make that happen with common household lighting used worldwide with E26 and similar E27 base?

The above near-universal type of lampholder has a propensity for the cardboard insulator to break down with age and/or careless handling by nimrods; this exposes the outer threaded ring of the lampholder to direct contact with the metal shell right where you grab to turn things on/off. This was the primary reason for the NA NEC going to polarized plugs as a standard on small appliances and lighting.

The fact it is too easy to cut/drill through both conductors and still manage to energize a metal body (especially with the Tim Taylor crowd) is why they pressed forward with double-insulated requirement for hand-operated power tools, which later also begat safety lampholders with a plastic body, but these have their own list of weaknesses.

I personally feel that makes a lot of sense, as long as you don't use multiphase power (as opposed to the center-tapped 240VAC system commonly used in NA) for general household stuffs. Which, honestly, I also feel is not a bad idea.

mnem