Test Equipment Anonymous (TEA) group therapy thread

[AVGresponding]

Oh this has pissed me off this has.

About 10 years ago I bought a nice Blundell Harling acrylic ruler here for general use. It eventually wore out i.e. all the markings started coming off. So I ordered a replacement a few weeks back. I stuffed it next to my new one and the markings are slightly out. Finally found my metal ruler to compare. Looks like I've been using a quite frankly incorrect ruler for the last 10 years. This might explain a few problems! 



Order top to bottom: New BH, Old BH, cheap chinese metal ruler.

Another "quality British product". Needs to be a turd emoji on this forum.

One can't expect a printed plastic ruler to be accurate. The markings are likely printed with either flexography  (I think the name gives away the potential issues here)  or screen printed  -again innately involving  the screen being elastically deformed during the printing process. Getting better than say 1/2 a mm in 300mm would be a tall order.

I wonder if evaporation/degradation of the plasticisers in the thing might affect its length over time..? I'm not familiar enough with the chemistry of these things to say for sure. I'd definitely trust a stainless rule to be more stable over time though.

@Specmaster
You got the £100 Tek 720 then 

Nope, I won it with my maiden bid. Now waiting for a reply from factory (David) to see if he wants it.

[med6753]

The NYC subway system plus 3rd rail operations into Grand Central Terminal are 600VDC. Not sure about other cities like Boston but wouldn't surprise me if they were DC too.

Most streetcars, light rail and underground is low voltage[0] DC, in Europe too. Until not too long ago, it was implemented with rotary converters.

In Germany, Switzerland, Austria, Norway and Sweden (and possibly a few more, but those I'm certain of) catenary voltage for normal trains is 15KV 16 2/3 Hz single phase. (Three-phase was experimented with, and a test track was built in Germany, where an AEG electric engine set a world speed record that took some time to beat.) It was chosen for its good match with the rpms convenient with the large motors of the time, and being 1/3 of 50Hz. For some railways in Sweden, like the "Malmbanan" (="ore railway") Luleå-Kiruna-Narvik, a special power station was built (in Porjus for the Malmbanan) that did generate the correct frequency in a single-phase system, but for most of the remainder of the country, there were rotary conversion systems fed from the 50Hz 3ph grid, the last such system delivered in 1978. They frequently were built moveable on railway cars, which normally were parked in bunkers adjacent to the line. (We sure like to put things we care about underground, we do.)



In the 80's, high voltage/power semiconductors for power modulation became good enough to permit conversion from 50Hz to 16 2/3Hz to be done in silicon, and that's been the norm ever since.

• In Sweden, "low voltage" is defined to be between 50 and 1000 volts. High voltage is above, and SELV is below.

A catenary designed today typically is at normal line frequency, and slightly higher in voltage, because that would be cheaper in the supply side.  The engines make DC of it as soon as it leaves the HV transformer anyway, to make 3-phase variable frequency for the drive motors.

Overhead catenary voltage here varies from 25kV/60Hz to 12KV/25Hz depending on what "legacy" (read: Bankrupt and long gone) rail line you are on which makes it a challenge for Amtrak in the Northeast corridor. It is mish-mash of old Pennsylvania RR, Jersey Central RR, New York Central RR, and New Haven RR. All those rail lines for passenger service are now Amtrak. Freight service is either CSX or Norfolk Southern.     

[Cerebus]

I wonder if evaporation/degradation of the plasticisers in the thing might affect its length over time..? I'm not familiar enough with the chemistry of these things to say for sure. I'd definitely trust a stainless rule to be more stable over time though.
Nope, I won it with my maiden bid. Now waiting for a reply from factory (David) to see if he wants it.

The impression I've always got is that the clear ones are a straight crystalline plastic - PMMA or polycarbonate - so no plasticisers involved. I've never dissolved one up and fed it into a GC/MS or HPLC so I don't know for a fact, and I haven't been lynched for gumming up someone's GC/MS or HPLC setup.

Edit: In fact I did have one ruler that had "shatterproof polycarbonate" printed across it in Letraset "Shatter". I seem to remember taking that as a challenge.

Shatter:

[AVGresponding]

Ok, but what if it oxidises? Adding a few billion oxygen atoms over a few years might increase its length by a teeny bit.

EDIT TO MATCH Cerebus' EDIT: It's not that much of a challenge, even. Simply slapping it hard and flat on a desk will make it do so.

[mnementh]

lord 'elp me... I think I understood that exchange. 

Simple, you have a wife and therefore understand the predictive compression algorithm that I used.

          Bwa-haaa-haaa!

Thanks for the belly laugh; I needed it. 

mnem
strewth; ev'ry word.

[AVGresponding]

Can't wait up for a reply; I was an hour and more late for work this morning, I'd rather not do it again tomorrow, it might be considered to be taking the piss...

[Cerebus]

Has anybody got any experience of Molex "Nano-Fit" connectors? They're the baby 2.5 mm pitch version of the classic Molex "Mini-Fit" that we all know as a PC motherboard power connector. (The ranges go: Mini, Mini Jr, Micro and Nano.)

I'm thinking of using them as the power and ancillary connectors for the GPSDO PCB - a step up from crappy 0.1" DuPont style (and more compact) and tougher than JST-whatevers. Anybody got anything good, or bad, to say about them?

[bd139]

If they are of Molex heritage they are probably flame emitting at some point in the future.

I’m going full on and just wiring everything with D-subs or SMA or BNC externally and anything else internally is soldered into cup pins and laced. I managed to score a bag of 500 pins a few years back for a fiver on eBay so I should probably use them . D-subs are keyed, reliable and good for half an amp per pin.

I have a large scary project on the go which will utilise this throughout.

[Cerebus]

Ok, but what if it oxidises? Adding a few billion oxygen atoms over a few years might increase its length by a teeny bit.

EDIT TO MATCH Cerebus' EDIT: It's not that much of a challenge, even. Simply slapping it hard and flat on a desk will make it do so.

Both pretty chemically stable and I'd have thought more likely to just fall apart spontaneously if they reached the level of degradation that was enough to produce a change in length. A quick cursory search suggests that PMMA is highly resistant to oxidation, even in the presence of UV (to the extent that it's even used as a protective coat to seal other more vulnerable plastics), polycarbonate not so much. I've personally seen polycarbonate used as safety glazing get quite cloudy after a few years facing the outside world. Sometime when we hit the doldrums here I'll tell you about the night that lead to the glass that was in that large window getting replaced with polycarbonate.

Polycarbonate is pretty tough stuff, used for crash helmets and safety glasses. PMMA on the other hand would definitely yield to a good thwack on the desk.

[0culus]

On today's edition of "I totally didn't need it, but I wanted it", I took the morning off work to go pick up this beast today (and an 8447D preamp that needs a new power switch). This is an -hp- 495A traveling wave tube amplifier. Heavy as hell, and contains lethal voltages. But super cool. The TWT is made by Watkins-Johnson who were a big name in TWTs manufactured for radar and EW applications back in the day.

[mnementh]

mnem
"they make a cream for that..."

[0culus]

mnem
"they make a cream for that..."

What's that sizzling sound I hear? 

[Wolfgang]

mnem
"they make a cream for that..."

What's that sizzling sound I hear? 

... with just a Watt ? Naaah ... But dont stare into waveguides ... 

[Specmaster]

@Specmaster
You got the £100 Tek 720 then 

Not guilty me lord, don't have a need for one now.

[mnementh]

mnem
"they make a cream for that..."

What's that sizzling sound I hear? 

... with just a Watt ? Naaah ... But dont stare into waveguides ... 

"...Momma always told me not to look into the eyes of the sun;
'But momma, that's where the fun is!!!'"

mnem
oh... and look who's done a cover of it... 

[Kosmic]

Its gone but the 10811As are better anyway.
The SC cut ones age upwards so after some decades it can happen that the tuning cannot get them down to exactly 10MHz. Stay away from seller silosurplus (sent two broken units but claims everything is tested).

Got a 10811-60111 with that problem. I'm thinking of using the oven for something else.

[mnementh]

 

WHAT COULD POSSIBLY GO WRONG...?   

 https://www.banggood.com/DANIU-60CM-Alligator-Test-Clips-Clamp-to-USB-Male-Connector-Power-Adapter-Cable-Wire-p-1157673.html

mnem
In other news... bang-em-good did finally offer me a full refund for those wrong test leads they sent me last month.

[med6753]

On today's edition of "I totally didn't need it, but I wanted it", I took the morning off work to go pick up this beast today (and an 8447D preamp that needs a new power switch). This is an -hp- 495A traveling wave tube amplifier. Heavy as hell, and contains lethal voltages. But super cool. The TWT is made by Watkins-Johnson who were a big name in TWTs manufactured for radar and EW applications back in the day.

Looks dangerous. Me like. 

[mnementh]

Uh-oh... looks like Papa Smurf is channeling another cartoon character...

mnem
*certifiable human cartoon*

[Wolfgang]

I disassembled one, and the crystal is a nonstandard copper-cased part fixed by a screw (see my thesis). If you have a Bliley BGSCH-61 or other replacement it would fit into the cavern (with some heat compound paste).

The crystal must be an SC-cut on 3rd OT in series mode, and the HP10811A has a b-mode suppression network that wont work with normal crystals.

[mnementh]

...and that's why DW always has purple smoke around him...? 

mnem
'tis crackers to slip a rozzer; the dropsy in snide.

[bitseeker]

...
WOW !! Thanks for that !! A one liner cpomment I could easily have missed when skimming 2+ pages worth of TEA ! Glad I took the time to read each and every comment ! 
...

Yes, reading this thread can be a challenge itself. Things go by pretty fast. Zoooom!

[bitseeker]

Introducing:



my new US Lab version beta 0.01.
about 8 meters x 3 meters, I can dance tarantella now.. uh feet, inches, sorry whaaat?
...

Woah! Jealousy-inducing spaaaaaace.

But, this is TEA. So, you won't have a dance floor for too long.

[bitseeker]

Found this little fellah in our local ebay 'Marktplaats'
was there for a while, looking at me with its snoopy eyes.. noone saw it i guess.. well what can you do.
so low balled it... and here it is 

Awesome, a 3469 buddy. I have the "A" version.

[bitseeker]

Saw a Fluke 8300A this weekend. While I was negotiating a price, someone paid full price for it. Ah, well.

Anyone from here grab it? It's got nice options.