Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Will print my own at that price 

[Black Phoenix]

Will print my own at that price 

Add a slot on the bottom to put a small magnet sheet and you have a magnetic parts holder. That's the great advantages of a 3D printer.

[xrunner]

Can you zip the .stl file and post it - I might like to try that. 

Depends what colour you paint it! 

Edit: next print. Designed myself. Parts tray for when I take test gear to bits. I found a few designs but I didn't like any so chucked this together. Has much more curved insides than the others meaning easier to get the parts out!

[bd139]

Will do. Let me print one first to make sure it doesn’t go to hell 

[bd139]

Will print my own at that price 

Add a slot on the bottom to put a small magnet sheet and you have a magnetic parts holder. That's the great advantages of a 3D printer.

That’s a good idea 

[xrunner]

Will do. Let me print one first to make sure it doesn’t go to hell 

OK I'm changing my PLA to white in anticipation. I have the fullest confidence your design is perfect. 

No rush. 

[bd139]

I haven’t got one right first time yet so see you on Wednesday 

[AVGresponding]

@med,
 Yes, Angela Gossow (Arch Enemy) had to be treated for nodules on her vocal chords. She was one of the pioneers of the style, and techniques have improved a lot, but I expect it's still hard on your body.

@bd139
I really like my UT139C, and given the model number, how could you even consider anything else?

@tggzzz & beanflying,
Guys please, I almost wish I never asked... The wasteful nature of SLA if you're only making small quantities wasn't apparent to me, now I know, I won't be going that route, even if it means lower resolution. I'll just have to forgo the pleasure of being able to make 2mm diameter spur gears...

I don't always listen to metal, I like most music, and Heilung are one of my favourites for chilling out.

Which I need atm... I opened the 1953A up to see what I could see, and what I saw was not good... a sea of tants!   
I gave them a quick check to see if any were shorted, and they aren't.
There is a power problem though; all the rails are low, and since the -12V and +5V both track from the +12V, that's my first port of call, made a list of caps and transistors to check, not today though.
On the plus side, though the back plate shows no options fitted, it does have the -04 TCXO. With the +12V rail at around 9.5V it's no surprise that the output from this is screwy. Hope it's not the TCXO pulling the rail low...

[mnementh]

Please forgive me for wandering off on a tangent during this fascinating discussion on audiostoopid but I actually spent a couple of hours at my bench today working on test equipment.   

I replaced the Tek power plug on the 184, which is a right pain in the ass, with a power cord, and no longer have to look at this:

.......snip.....
Tggzzz has one of these beasts too and should be able compare his with yours to determine if in fact you have an issue.

It is mainly a case of how much time I'm prepared to invest. I didn't even bother to look at the PSU ripple; that might be an easy win.

If you look at the diagram, the whole thing is inherently "touchy". For example, there is insufficient signal power to drive all the stages simultaneously, and the divide-by-2 and divide-by-5 stages are analogue. Transistors were expensive, ICs unknown, and those division stages used only 3 transistors apiece; with flip-flops 8 transistors (and quite a few resistors) would have been needed.

The division principal was that each input pulse dumped a charge glug onto a capacitor. After 5 glugs the voltage had risen sufficiently that it triggered, discharged the capacitor and provided the pulse for the next stage. Since the glug size is somewhat dependent on the input pulse, it isn't surprising that there is interaction between stages.

mnem
"Impairing productivity since Nineteen mumblety-mumble..."

[mnementh]

Random question for everybody. I need a suggestion for a cheap and decent DMM from aliexpress/eBay. Something that has a micro amps range, works properly without any weirdness, has thermocouple. Doesn’t need crazy resolution. 3.5 digits is fine. I’m going to write up an article on a cheap RF test bench for sprat. We’re in a golden age of cheap so makes sense to promote this.

Aneng AN8002 comes with a thermocouple. Costs US$10-20 depending on when/where you buy.

mnem
*Pokemon widda son time*

[bd139]

Cool will take a look at that. Thanks 

[worsthorse]

For this purpose I have one of these:



https://www.buerklin.com/en/Products/Test-%26-Measurement/Measurement-accessories-in-our-product-portfolio/Storage-and-mounting-for-measuring-instruments/Montagegittermatte-610-x-370-x-20-mm/p/02L6543

Not cheap but never regretted to buy one.

I use the plastic containers from this supermarket mochi we buy sometimes...



It is like a muffin tray, only white, plastic and small.

[mnementh]

Cool will take a look at that. Thanks 

Yup. I tossed the 8008 in my tool bag as a third meter without thinking; now I regret not taking the 8002 as I have zero thermometers I can use to reality-check my T12 OLED station. -20~1000℃ range, but integer values only IIRC. That may be a problem for your application; I don't know.

mnem
 

[tggzzz]

The wasteful nature of SLA if you're only making small quantities wasn't apparent to me, now I know, I won't be going that route, even if it means lower resolution. I'll just have to forgo the pleasure of being able to make 2mm diameter spur gears...

That is entirely sane! I wouldn't have one either, and nor would I recommend that another beginner had one. The local hackspace believes, correctly in my view, that even with multiple people using SLA, it wouldn't be practical for them to have their own SLA printer due to the chemicals involved.

Ditto printing brass, ditto printing nylon.

Consequently I use a commercial printshop, usually Safeways or DirtyPCBs.

[worsthorse]

Letting it warm up for two hours    as suggested in the service manual, I was pleased to find that the local oven-ized 10MHz oscillator running at a steady 10,000,032 Hz and drifting no more than +/- 1Hz. While that is well within spec, we will see if we can do better a little later. And to be honest, the oscillator was running at that frequency within ten minutes of turning it on and didn't move after that.

And how accurate did it need to be for contemporary analoge scopes? Their spec was usually 2%!

But at 500ns, things start to look not so good:
Same for mixed markers (500ns and 100ns):

There are lots of trimpots that interact with everything else. Maybe improving the PSU ripple will help.

It is not surprising that there's cross talk here, nothing in the box is shielded:
...
I will start by looking at the power supply more carefully tomorrow and see if I can clean it up. It has been a while since I worked on anything generating frequencies like this...

It is also worth understanding which parts are and aren't powered up on the various settings. Quite apart from overall power dissipation, the available signal power was insufficient to drive all subcircuits at the same time.

agree on all fronts. i am fairly certain that this box, without doing anything other than running through the cal procedure, will meet the manual specifications. the noise, crosstalk, drift, and so on won't make any difference if one is using this for its intended purpose, circa 1975. 

but if i can make it do better, i probably will because, well, i can. 

the circuit design is really pushing the bounds of price/performance/size for that era, which also makes it an interesting thing to study, even if i can't improve the performance. building countdown timers using discrete capacitors as "ladles" and "buckets"  and transistors as gates is pretty neat. the manual circuit description and schematics are worth looking at even if you don't have one. 

[bd139]

Cool will take a look at that. Thanks 

Yup. I tossed the 8008 in my tool bag as a third meter without thinking; now I regret not taking the 8002 as I have zero thermometers I can use to reality-check my T12 OLED station. -20~1000℃ range, but integer values only IIRC. That may be a problem for your application; I don't know.

mnem
 

temperature will be measuring iron tips and transistor temperature. 1oC resolution is good enough. It only has to be better than the finger sizzle test. Aliexpress is have a discount day in 14h so I will bag one then for just under £9 and see what the deal is 

[tggzzz]

The division principal was that each input pulse dumped a charge glug onto a capacitor. After 5 glugs the voltage had risen sufficiently that it triggered, discharged the capacitor and provided the pulse for the next stage. Since the glug size is somewhat dependent on the input pulse, it isn't surprising that there is interaction between stages.

If you look at the circuit descriptions of high resolution meters, "glug" seems to be standard terminology. To grossly oversimplify, there is a clock (derived from the mains frequency) that increments a counter and dumps a glug of charge onto a capacitor. When the capacitor voltage equals the input voltage, the counter stops and the count is displayed.

[worsthorse]

Please forgive me for wandering off on a tangent during this fascinating discussion on audiostoopid but I actually spent a couple of hours at my bench today working on test equipment.   

I replaced the Tek power plug on the 184, which is a right pain in the ass, with a power cord, and no longer have to look at this:

.......snip.....
Tggzzz has one of these beasts too and should be able compare his with yours to determine if in fact you have an issue.

It is mainly a case of how much time I'm prepared to invest. I didn't even bother to look at the PSU ripple; that might be an easy win.

If you look at the diagram, the whole thing is inherently "touchy". For example, there is insufficient signal power to drive all the stages simultaneously, and the divide-by-2 and divide-by-5 stages are analogue. Transistors were expensive, ICs unknown, and those division stages used only 3 transistors apiece; with flip-flops 8 transistors (and quite a few resistors) would have been needed.

The division principal was that each input pulse dumped a charge glug onto a capacitor. After 5 glugs the voltage had risen sufficiently that it triggered, discharged the capacitor and provided the pulse for the next stage. Since the glug size is somewhat dependent on the input pulse, it isn't surprising that there is interaction between stages.

mnem
"Impairing productivity since Nineteen mumblety-mumble..."

Investment: the action or process of using time or money to generate more of something or other than one had before investing. Repairing/fixing/cleaning/calibrating whatever obscure, no-longer-used piece of test equipment am I currently working on is a lot of things - fun, interesting, frustrating, satisfying, pointless - but investment? I don't think so!   

And for this particular piece of TE, all that stuff you mentioned about the design and implementation are precisely what I find interesting about the 184 and why I will waste countless hours poking at it.  I know.   

[tggzzz]

Snipped point that I agree with.

the circuit design is really pushing the bounds of price/performance/size for that era, which also makes it an interesting thing to study, even if i can't improve the performance. building countdown timers using discrete capacitors as "ladles" and "buckets"  and transistors as gates is pretty neat. the manual circuit description and schematics are worth looking at even if you don't have one.

... and even entertaining ...

[tggzzz]

And for this particular piece of TE, all that stuff you mentioned about the design and implementation are precisely what I find interesting about the 184 and why I will waste countless hours poking at it.  I know.   

I know that syndrome only too well, albeit with different bits of kit

I seem to have a fetish for 1502s, and many digit voltmeters.

[ArthurDent]

Fluke 8125a:

Putting test equipment in those bombproof military cases worked great and preserved a lot of good stuff for us to buy on the surplus market. Some of the problems are that the cases added weight and bulk. I use to own a USM-339 (HP1700B) dual trace scope in a bright yellow case. I just checked a USM-326A Ballantine Lab frequency counter and it is quite stable and accurate and goes up to 350Mhz which isn't too bad for a counter made in 1977.

[Johnboy]

@med,
 Yes, Angela Gossow (Arch Enemy) had to be treated for nodules on her vocal chords. She was one of the pioneers of the style, and techniques have improved a lot, but I expect it's still hard on your body.

It's surprising that the vocalist they handpicked to replace her didn't have similar problems. I'm no an Arch Enemy fan myself, but... ye gods... this woman certainly upped the ante in several ways.

[bd139]

Tray done. Works nicely. If anyone wants the STL, PM me and I'll send you a link 



Embiggen it for bigger stuff 

[Specmaster]

That looks pretty good actually. Got UT139C in list as well. That seems to have somewhat better protection than average.

Check out the meters that Joe Smith has tested and rated for some other ideas.

[xrunner]

Tray done. Works nicely. If anyone wants the STL, PM me and I'll send you a link 

Embiggen it for bigger stuff 

Great, got the file. May do same size or shrink it a little.