Test Equipment Anonymous (TEA) group therapy thread

[BU508A]

curve tracer voltage / current loop design. Currently uncompensated so this will no doubt oscillate like a wild monkey masturbating



sw1 sets voltage or current steps. sw2 sets step size.

Edit: looking at bias currents and stuff I’m going to have to add range switching for current sense for micro amp ranges. This gets really complicated really quickly. Need to build something that scales from 1uA to 10mA with better than 5% accuracy, universal stability under load level changes and a fair compliance range 

You might want to consider a diamond transistor for that class B output stage, saves on the op amp rushing to turn one output transistor one and one off, and gives you better linearity for the cost of two jellybean transistors and two resistors without going all full blown V_BE multiplier. Like this:



I've put 2N3094 and 2N3906s but it can be anything really. In fact something a bit slower is advantageous as our old friends have so much more gain bandwidth than the BD139/140 pair it can get a bit hairy.

And yes, I can't manage to get my emitters in the right place first time today - it's been one of those days.

Please forgive me my ignorance, but what is a "diamond transistor"?

[Wolfgang]

"Diamond Transistor" is just a nickname of the circuit he used.

AFAIK, they also made transistors of "real" diamond, but I dont know if they made it into any practical use.

[coppercone2]

no diamond transistors available for sale yet

anyone got a source?

[tggzzz]

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

Swimming is another option. Has benefits of being low impact and you can change the effort and duration.

agreed, however public pools/baths are a potential COVID issue and may be closed, or unsafe for German women to swim in.

The Baltic around this area is known to be somewhat dangerous due to strong currents, and besides, it's effing cold.

But safe for other nationalities?

Wetsuits or drysuits are the traditional way of keeping warm(er) in water. But the Gulf Stream doesn't reach the Baltic!

OTOH you could always try bog snorkelling, a traditional English sport.

[nfmax]

The picture says it all

[BU508A]

The picture says it all

Insider for Germans: "Agilent, Rigol - Hauptsache Oszilloskope!" 

[tggzzz]

curve tracer voltage / current loop design. Currently uncompensated so this will no doubt oscillate like a wild monkey masturbating



sw1 sets voltage or current steps. sw2 sets step size.

Edit: looking at bias currents and stuff I’m going to have to add range switching for current sense for micro amp ranges. This gets really complicated really quickly. Need to build something that scales from 1uA to 10mA with better than 5% accuracy, universal stability under load level changes and a fair compliance range 

I doubt a 741 can be used to measure high-side current; instrumentation amps are traditional, but ISTR there's an opamp with a ridiculously high input voltage spec (i.e. >>supply voltage) that can be used for this.

Will you need a negative supply?

If you need a higher voltage output, consider this circuit ...


FFI, see the current "High Voltage op amp" thread in s.e.d

[Saskia]

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

Swimming is another option. Has benefits of being low impact and you can change the effort and duration.

agreed, however public pools/baths are a potential COVID issue and may be closed, or unsafe for German women to swim in.

The Baltic around this area is known to be somewhat dangerous due to strong currents, and besides, it's effing cold.

But safe for other nationalities?

This entirely depends on where you are. One reason for not getting any exercise is the lack of personal safety. There have been assaults even on the company parking lot.
So, no. I don't want to it up with the crap I am getting in public parks, pools, etc.

[tggzzz]

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

Swimming is another option. Has benefits of being low impact and you can change the effort and duration.

agreed, however public pools/baths are a potential COVID issue and may be closed, or unsafe for German women to swim in.

The Baltic around this area is known to be somewhat dangerous due to strong currents, and besides, it's effing cold.

But safe for other nationalities?

This entirely depends on where you are. One reason for not getting any exercise is the lack of personal safety. There have been assaults even on the company parking lot.
So, no. I don't want to it up with the crap I am getting in public parks, pools, etc.

Nasty. But isn't that also a problem with walking?

[bd139]

curve tracer voltage / current loop design. Currently uncompensated so this will no doubt oscillate like a wild monkey masturbating



sw1 sets voltage or current steps. sw2 sets step size.

Edit: looking at bias currents and stuff I’m going to have to add range switching for current sense for micro amp ranges. This gets really complicated really quickly. Need to build something that scales from 1uA to 10mA with better than 5% accuracy, universal stability under load level changes and a fair compliance range 

I doubt a 741 can be used to measure high-side current; instrumentation amps are traditional, but ISTR there's an opamp with a ridiculously high input voltage spec (i.e. >>supply voltage) that can be used for this.

Will you need a negative supply?

If you need a higher voltage output, consider this circuit ...


FFI, see the current "High Voltage op amp" thread in s.e.d

It's fairly low voltage there as it's step generator only. All under 15V. I've got an INA series instrumentation amp somewhere with built in laser trimmed precision resistors which is getting substituted in when i find it. Bias current and offset are major issues rather than voltage on that bit. This has to source / sink a max of 100mA (for version 1 anyway) with about 5v of compliance or voltage steps up to 10V.

The high voltage supply is much simpler and is just a simple voltage controlled voltage regulator driven from 0-5v in and 0-200v out with a BU508A or similar on it. Only needs to source current fortunately so nothing fancy required!

Edit: place your bets. Broken or not broken? Hameg HM605:

[Saskia]

in general yes. It's entirely dependent on where you are in Germany.  Right now I am in the northeastern part, where they did not have such an influx of this specific ethnic group. They have a lot of Russians instead, but those generally leave you alone.

When I am back at work, walking will no longer be an option.

In other parts of the country the sharia police (muslim enforcers) will ask you why you are on the streets aloneand not accompanied by a male, why you are not wearing a nikab, etc. Happened to me when I was fpumping gas.

But this is stuff they usually do not report.

Let's not dive into this topic.

[McBryce]

Anyone looking for a HP3488 for extremely cheap? https://www.ebay.de/itm/203100035645

McBryce.

[bd139]

Well HM605 works and is not damaged despite the shitty packaging. 1MHz cal signal...



Someone has already repaired it at some point. I think this needs reworking TBH:



On to the next box of crap that arrived today (I had a few deliveries!!!) ...

[bd139]

Right. The Racal 9916 turned up and immediately hurled smoke everywhere on power up. Looks like something is buggered. Probably a short tant somewhere. 

-5V rail troubles!

Edit: found it right away. 47uF electrolytic poked in it and it works. Have left smoked resistor in as it's still measuring fine 

Some pictures... working OCXO for once:



Smokey blue resistor:



Fixed!



More to come!!!

[SilverSolder]

Someone seems to need a chastity belt on their eBay account! 

[med6753]

This is local to me, next town. 5 massive boat anchors and a series 500 scope cart. Been drooling over it for the past 24 hours but there's no way I can accommodate all of them unless they reside in a damp garage. And I can't bring myself to do that.

Now if they would be willing to relist it as one 515A, one 545A, and the cart for approx $250 USD they would have green backs in hand today. It has been listed for quite a while but I have my doubts that they would be willing to split the lot.

Still debating. 

They claim that they all work but I'm not buying that.

https://www.ebay.com/itm/REDUCED-ENTIRE-LOT-of-Oscilloscopes-3-545A-1-535-1-515A-1-Type-500-53A-kart/303196264366?hash=item4697e7d7ae:g:LIwAAOSwIipdDD69       

[bd139]

Get it before the tube snatchers get it! 

More crap. Decided to buy some wire for once rather than using offcuts of things all the time.



And the thing I was really waiting for, the unfinished guts of another radcom spectrum analyser...

[Fungus]

I gotta admit... I really don't get the high reverence for that family of [FLUKE] meter; aside from lower standards of the time.    Those switches were a major POF, and as the signal actually passes through the switches, hugely dependent upon them for quality of measurement.

Weird that they just keep on working forever and never seem to need calibration. 

(the switches are actually self-cleaning types)

[mnementh]

did some long walk today including about 4 km through sand. Tired as hell.

Mmmmhmmm... so what was on the other end of the walk...? Something Nakamichi...? 

mnem
 

The end of the road ...

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

Oh, I was trying to think of something that could make you volunteer for that misery... but I imagine you've been doing some re-evaulatin' lately what with recent events, so a desire for some real self-improvement does make sense.

Small steps, one step at a time, etc... Last round I managed to lose 40lbs and got up to 1.5Km a session before my back would start shrieking in fiery pain; looks like I have a nice big lawn now that will burn many ergs, so we'll see what trade-offs I can make while still not crippling myself.

It sucks when your entire life becomes defined by a limited amount of "verticalness" at your disposal every day...

mnem
"Life is hard; fortunately it is also short." ~козака́ proverb

[mnementh]

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

(Electric) bike could be an option, the weight goes on the sattle and your knees will thank you.
Of course you can get a cheap Lead battery one and convert it to LiPo...

Where...? Seriously... I've been looking; and the cheap, no-battery kits start at fucking $400 for something I wouldn't trust to haul my fat arse across the living room, much less up even a 10% incline.

I've seriously been considering building something using a model aircraft motor and a lot of 3DP abuse.

mnem
 

[mnementh]

Seriously, trying to get back in shape and get rid of some kilos by exercise. If yer too heavy to go jogging, walking seems to be an option.

(Electric) bike could be an option, the weight goes on the sattle and your knees will thank you.
Of course you can get a cheap Lead battery one and convert it to LiPo...

I don't see what the benefits of an electric bike are for health. Get a normal one and take it a bit easy at first, then start tackling the hills. In my mind the biggest problem is avoiding some crazy person driving a car and knocking you off. Mountain bike riding tends to avoid that issue so long as you don't get too confident and go plummeting down steep slopes!
Start here 😉 : https://youtu.be/yotOZVELSMc

The reason eBikes have taken off is a simple rationalization: "Since I barely have time to drive anywhere, when will I find time to bicycle unless I do some errands at the same time? But then if I overextend myself, I wind up walking home, carrying whatever I got on my errands and... and... and..."

Yes, it's a trap. And most people never actually manage to make "the plan" work, because eBike hassle, regrets over the ridiculous amounts of money, being "cycling shamed" by some hipster on a fixie, etc...

In my case, it's because the cycles I can comfortably ride (my back will not tolerate more than 5 minutes hunched over on a mountain bike) don't usually come in a multi-speed variant, so I'm stuck either  modding a beach cruiser with a expensive wide-rim 5-7 gear cluster wheel or trying to turn a cheap mountain bike into a beach cruiser. Neither works out very well. Closest I've come is putting BMX headstock & bars on a mountain bike; still looking for a tolerable seat for that butt-ugly beast.

I seriously considered just sucking it up and buying a cheap fatbike, but there is no such thing up here, as they NEVER go out of season. Crazy canucks ride 'em in the snow.    The cheap ones are a grand; right up to $5K & more for off-the-rack models from the boutique brands. 

Seriously; fatbikes & eBikes have gone fucking crazy cost-wise... combining the two is a recipe for wallet evisceration.

mnem
moo.

[mansaxel]

Ok, lowball (not Ferengi class) offer plus insane amount of shipping accepted on a 6206 in sorry state (For parts).  The USD is weaker to the SEK now, so is somewhat bearable (The fact that Covid-19-related deaths per capita is higher in the USA than Sweden now probably influences this). Guesstimated late September arrival. Pics and state report then.

[mansaxel]

I seriously considered just sucking it up and buying a cheap fatbike, but there is no such thing up here, as they NEVER go out of season. Crazy canucks ride 'em in the snow.   

Same here, people switch from racing bikes to MTB'en when snow arrives, fit spike tyres and keep on biking. It does help that at least in Stockholm bike lanes are prioritized for snow clearance.

[Cerebus]

It strikes me that a recumbent bicycle might be an option for those who have a back problem or a saddle problem. An old friend/colleague of mine who had a mullered back courtesy of a major motorcycle crash (lots of titanium pins and months in hospital) used to use one successfully and in comfort.



However, speaking as a man who used to happily cycle in London rush hour traffic (I used to race Porches between the traffic lights on Holland Park Avenue and win^*) I'd be terrified of being that low down and low visibility on roads where there were any powered vehicles other than motorbikes around.

^*This isn't as hard as it sounds, the spacing of traffic lights along Holland Park Avenue is short enough that the acceleration curve of a fit man on a bicycle is better suited than the acceleration curve of a Porsche 911 Turbo. The fun was in seeing the look of frustration on the faces of Yuppies in flash cars being beaten in a race, repeatedly, by a scruffy student on a bicycle in jeans and a T-shirt.

[BU508A]

I've ordered today two of them. Curious, if they are any good.

https://www.aliexpress.com/item/10000132950232.html



Triax 3-lug male connector.