Test Equipment Anonymous (TEA) group therapy thread

[mindcrime]

As somebody who is, on one hand, an electronics enthusiast / hobbyist, and on the other hand a former firefighter and firefighting instructor, I have to say, certain aspects of this thread make me a little nervous.   

All I can say is, be REALLY F'IN SUPER CAREFUL with highly flammable substances.  Yeah I know, Mötley Crüe frickin' set themselves on fire during their early concerts just to wow audiences... but generally speaking, there's a reason we encourage people to not "play with fire".   

That's nuthin. When you got a few hours go way back in this thread and read some of bd139's exploits with fire. It will make your hair stand on end. 

One day... ONE DAY... I fully intend to go all the way back to the very beginning, and ready every. single. post. in. this. thread.

It might take me the rest of my natural life, but I feel like it's.. I dunno, a Vision Quest, or something.   

[bitseeker]

Yes. A pilgrimage of sorts. We'll have to make a special, new award if you succeed.

[DaJMasta]

IPA is pretty nasty stuff if it goes up. Can’t see the flames

That's getting its color from the impurities on the surface burning off - if you use an alcohol lamp with a wick it will look similar because the color is coming from the burning wick.  The IPA itself has a faint blue flame, if you just like put it in a clean glass vessel and light it so it's only the alcohol burning.

On the plus side, if your burning IPA comes into contact with something you care about, the flame color should change and at least then you can see it   

[beanflying]

Speaking of Fire Hazards and going off topic - again 

Today is the day to clean out the detritus from the back end of my baby sample coffee roaster before it catches fire  The Chaff (think peanut husks) and miscellaneous floaties at 200+C is known to go up in smoke and the former owner of this one had a near escape before I got it.

Major reason to drop the back off it to finally replace the suspect noisy multimeter cheapy thermocouple with something more suited for the job.

Chaff goes where it wants and where you don't want. 

[mindcrime]

Damn... if you lookup "Fire Hazard" in a dictionary, there's probably a picture of that thing in there! 

 

[beanflying]

Damn... if you lookup "Fire Hazard" in a dictionary, there's probably a picture of that thing in there! 

 

Mine is 'clean' compared to where some rocket scientists let theirs get to https://www.home-barista.com/home-roasting/hottop-roaster-caught-fire-t47370.html

The theory is chaff should never get here but on most roasters including the big ones it does.  There is a temperature safety fuse fitted to them but when the beans are fully exothermic it is to late.

[VK5RC]

Well an evening aboard the fail train for me. Finished off the Philips power supply refurb. Connected it up, Meeeeeewwwwwwwwwww it went and then I shut the power off. After some poking around I discovered I'd put the 38V rail capacitor in arse about face. Schoolboy error. Measuring the ESR of the cap after pulling it, it's duff - over 10 ohms. Dig around in the junk box, all my 100uF caps only go up to 35V. Fuck! 

Edit: Incidentally I fired it up on the HP 6286A rather than on the mains. That didn't even hum with a couple of amps leaving it!

The Tek gods continue to give you bad karma. 

bd I think you need to appease the Gods - something like a sacrifice - no naked virgins easily to hand here - but hurling a 'parts unit' over a good cliff might help - or hitting it into pieces with a big hammer - always worked for me!
Don't forget the magic incantation - 'f**k you, you ba**ard' as it hurtles away.
I feel better already!
Rob

[bsfeechannel]

The other day I mentioned I had another small wood working project on tap. Well, here it is...ready for stain and poly. It is TEA related. If you can guess what it's for you will be granted genius of the day. Guess wrong and there's no penalty.

Once it's done I will reveal it's purpose.

I very much enjoyed the pictures of your electronics lab. Is there also a woodworking shop you'd like to show us too?

[mindcrime]

UUgh. Remind me to never buy a home coffee roaster.  I'll just keep buying my beans pre-roasted and pre-ground. Better yet, I'll just swing by Starbucks and buy coffee pre-made, and ready to drink! 

[beanflying]

UUgh. Remind me to never buy a home coffee roaster.  I'll just keep buying my beans pre-roasted and pre-ground. Better yet, I'll just swing by Starbucks and buy coffee pre-made, and ready to drink! 

Heathen  Charbucks isn't coffee and preground isn't fresh. 

[worsthorse]

Spent the evening working on the 501A. After recapping, worked my way through the circuit checking waveforms, which look as good as can be expected given the design. As I fired up the soldering iron to do the calibration, SWMBO stopped by the bench, hun this timer is driving me crazy, can you fix it?



Took it apart, cleaned it, reassembled it. No longer crazy-making. SWMBO is happy; I, too, then am happy. Excellent! Back to the 501A.

Did I mention a soldering iron was required in the calibration procedure? Yes, I did. Turns out that you have to short the emitters of three transistors to the 5VDC rail before...



... adjusting the trimmer pot that controls the feedback loop in the step voltage circuit



After adjustment, step voltages from .2 to 5 volts are all +/- 1%. Not bad   

Unsolder that wire and install another one so you can zero the offset voltage:



Also not bad. Finally, reassemble the box, then remember you forgot to remove the jumper you installed to set the offset voltage, dis-assemble the box, remove jumper, reassemble box. 

Finally, calibrate the scope H and V sweep to the 501A, stick a 2N2222A into the socket and yes ma'am it does seem to work just fine.   





I think I can declare this one fixed.

[jjoonathan]

The IPA itself has a faint blue flame, if you just like put it in a clean glass vessel and light it so it's only the alcohol burning.

This was a sealed 91% IPA bottle and a new petri dish, cleaned with acetone, isopropanol, distilled water, and isopropanol again, twice, using a fresh box kimwipes. The yellow flame was extremely uniform throughout the duration of the burn. At no point, even when starting or running out of fuel, did it ever resemble a methanol fire. I'm about 80% sure at this point that this is just confusion with methanol. The 20% is for possibilities like an unmentioned flame-producing additive, the azeotropic water being responsible for polymerization, etc.

Still, this result matches with my chemical intuition: upon heating, a three carbon molecule gives you plenty of room to form alkenes, polymerize into soot, become incandescent, and form a happy yellow flame. One carbon does not, which is why methanol behaves the way it does.

[med6753]

The other day I mentioned I had another small wood working project on tap. Well, here it is...ready for stain and poly. It is TEA related. If you can guess what it's for you will be granted genius of the day. Guess wrong and there's no penalty.

Once it's done I will reveal it's purpose.

I very much enjoyed the pictures of your electronics lab. Is there also a woodworking shop you'd like to show us too?

If there was a woodworking shop I'd show it. But alas, there isn't. I have typical tools plus the usual hand held power tools such as jig saw, drill, skill saw, sander, etc. And up until 6 months ago didn't even have a garage to work in. Most of my woodworking had to take place outside, even in winter. 

Edit....my "woodworking shop" is contained within those several totes plus tool boxes not shown.

[med6753]

UUgh. Remind me to never buy a home coffee roaster.  I'll just keep buying my beans pre-roasted and pre-ground. Better yet, I'll just swing by Starbucks and buy coffee pre-made, and ready to drink! 

Heathen  Charbucks isn't coffee and preground isn't fresh. 

StarSUCKS. 

[Specmaster]

If you can't see it it's not really a problem, is it? Just like electricity, come to think of it.

True, and because you don't flood the pcb with it and that it evaporates fast, risk is minimised. You only need to apply to the parts that you think are suspect in a very small area at a time. Because you use a current limited supply you know that dangerous currents and therefore sufficient to allow tants for example to combust isn't possible so ignition is not likely. The faulty part will be warmer then others in the area and so the evaporation will be more visible on that part. Also because the PSU has current limiting, as soon as it reaches the faulty part the voltage drops to virtually zero but the current still flows thus the localised heating affect above the ambient will still occur.

If it was half as dangerous as has been suggested then why do so many people do it on a regular basis without incidents? Like handling electricity you need to take care and not limiting the current is asking for trouble, so one has to be sensible as always.

Sent from my POT-LX1 using Tapatalk

[mnementh]

i didnt know TEA is one of courier service in China. its an outbreak..

Not sure, if T.E.A. is a good acronym for a courier service. To me, it sounds too much like DEA. 

Or worse yet, DOA... 

As somebody who is, on one hand, an electronics enthusiast / hobbyist, and on the other hand a former firefighter and firefighting instructor, I have to say, certain aspects of this thread make me a little nervous.   

All I can say is, be REALLY F'IN SUPER CAREFUL with highly flammable substances.  Yeah I know, Mötley Crüe frickin' set themselves on fire during their early concerts just to wow audiences... but generally speaking, there's a reason we encourage people to not "play with fire".   

That's nuthin. When you got a few hours go way back in this thread and read some of bd139's exploits with fire. It will make your hair stand on end. 

Or med "cookin' with propane"... or me ummm... growing my eyebrows back. In my defense, I too am retired firefighter of almost a decade service. 

If you want to talk about fire hazards, I've done some metal soldering with an oxyacetylene torch. Fire brick lined work area is basically required and you keep ALL flammables far away.

You don't solder with oxy-acetyl. Too hot; will burn the shit out of the solder. Braze, yes. Gas welding, yes. What they call soldering done on refrigerant lines is actually brass-silver alloy, so also brazing. The difference is how close to the melting temperature of the parent metal you have to get to make a bond; with brazing, you actually oxidize the metal and in the process make an alloy with the brazing rod.

Recently hosed-down concrete or even dirt/gravel workspace is perfectly safe for cutting or welding. Most shops use plastic welding curtains to restrict sparks from oxy-acetyl cutting and arc welding. Of course, flammables in the flammables cabinet is also SOP.

mnem
*Fire resistant*

[Specmaster]

It’s the thing that replaced Shutl. Think it’s based in Spain.

Glad you got the reference

Oh hell yeah, I got the reference alright, strange that because I was thinking of asking if you were comfortably numb yet 

[Brumby]

UUgh. Remind me to never buy a home coffee roaster.  I'll just keep buying my beans pre-roasted and pre-ground. Better yet, I'll just swing by Starbucks and buy coffee pre-made, and ready to drink! 

Heathen  Charbucks isn't coffee and preground isn't fresh. 

How to enrage a Bean.... just mention this:  "Blend 43"


.... Then run like hell.

[Mr. Scram]

True, and because you don't flood the pcb with it and that it evaporates fast, risk is minimised. You only need to apply to the parts that you think are suspect in a very small area at a time. Because you use a current limited supply you know that dangerous currents and therefore sufficient to allow tants for example to combust isn't possible so ignition is not likely. The faulty part will be warmer then others in the area and so the evaporation will be more visible on that part. Also because the PSU has current limiting, as soon as it reaches the faulty part the voltage drops to virtually zero but the current still flows thus the localised heating affect above the ambient will still occur.

If it was half as dangerous as has been suggested then why do so many people do it on a regular basis without incidents? Like handling electricity you need to take care and not limiting the current is asking for trouble, so one has to be sensible as always.

Sent from my POT-LX1 using Tapatalk

I was joking but squirting flammable liquids on a live PCB does sound like a risk. You may not burn down your house every time, but it'd definitely be a hard one to explain to your insurer when you do.

[beanflying]

UUgh. Remind me to never buy a home coffee roaster.  I'll just keep buying my beans pre-roasted and pre-ground. Better yet, I'll just swing by Starbucks and buy coffee pre-made, and ready to drink! 

Heathen  Charbucks isn't coffee and preground isn't fresh. 

How to enrage a Bean.... just mention this:  "Blend 43"


.... Then run like hell.

When people go and stay there their taste buds are beyond salvation, only pity applies.  Drinkers of $tarchucks do at least have some hope of redemption 

[med6753]

It’s the thing that replaced Shutl. Think it’s based in Spain.

Glad you got the reference

Oh hell yeah, I got the reference alright, strange that because I was thinking of asking if you were comfortably numb yet 

And after all these years that black strat still sounds amazing.

[Specmaster]

True, and because you don't flood the pcb with it and that it evaporates fast, risk is minimised. You only need to apply to the parts that you think are suspect in a very small area at a time. Because you use a current limited supply you know that dangerous currents and therefore sufficient to allow tants for example to combust isn't possible so ignition is not likely. The faulty part will be warmer then others in the area and so the evaporation will be more visible on that part. Also because the PSU has current limiting, as soon as it reaches the faulty part the voltage drops to virtually zero but the current still flows thus the localised heating affect above the ambient will still occur.

If it was half as dangerous as has been suggested then why do so many people do it on a regular basis without incidents? Like handling electricity you need to take care and not limiting the current is asking for trouble, so one has to be sensible as always.

Sent from my POT-LX1 using Tapatalk

I was joking but squirting flammable liquids on a live PCB does sound like a risk. You may not burn down your house every time, but it'd definitely be a hard one to explain to your insurer when you do.

Isn't everything a risk? But who in their right mind would squirt flammable liquid onto a live PCB?  I'd hardly call a PCB, removed from the equipment, in a well ventilated room with just a single supply rail connected but switched off, PSU set to a low current, and as everyone knows a decent bench power supply when set in constant current mode, will when connected onto a short circuit cause the voltage to drop almost zero so there is extremely little energy to create a spark.

I don't see how a PCB thus connected could be honestly considered to be "live", there is absolutely zero chance of the PCB operating normally under such test conditions as it is starved of the other supply rails and also of the energy it would normally consume.

This is the basic concept of how intrinsically safe equipment operates in areas of extremely high risk of explosion as a result of overheating and or a spark, it does so be keeping the voltage low and current low as well and it is interesting to note that the following link https://www.omega.co.uk/technical-learning/understanding-what-is-meant-by-intrinsically-safe.html it states the voltage is generally kept below 29v and the current below 300mA by protection devices and in general most such equipment would typically be rated at 24v and a simpler way would to think of it would be to keep the power below 1.3W.

Here is an extract from that link
How Does Intrinsic Safety Equipment Work?
Avoiding ignition entails minimizing both the available power and the maximum temperatures. Defining the maximum level of available power is complex, but in general terms can be considered as meaning voltage less than 29V and under 300 mA. A simpler view is to say that power must be less than 1.3 W. (Note that much instrumentation requires 24V and can often be designed to draw less than 500 mA; sufficient to meet IS certification in many situations)

So in real terms, providing people take sensible precautions and use decent equipment and do not squirt the liquid onto a live PCB then they should be OK. The method is that you have the PCB switched off, pour a little liquid around the part you suspect of having the short (the key here is a little, just like using flux, just enough for the part in question) and switching the power on and watching to see the part dries out before the residue liquid around it, if so then it signifies that the part is getting hotter the the parts/area around it and is more then likely to be your faulty part.

This technique is especially useful on PCB's stuffed full of SMD devices as was demonstrated in the video examples given where it is less easy to disconnect a leg for testing in the normal fashion, especially on items such as chips.

Fluke for instance actually make handheld DMM's for testing purposes within such environments for working on equipment to carry out vital repairs etc.   

[med6753]

Progress on the 485....

The fixed intensity issue was my fault. I forgot to reconnect R1567 when I was troubleshooting the +15V short. 



The scope now has a sharp trace. I verified the PSU voltages and they are in spec although I will eventually recap it. Many of the controls are gummed up and dirty so deoxit to the rescue. I burning smell upon first power up has not returned and I don't know what it was. I'm sure sooner or later it will rear it's ugly head.

New issue. Absolutely no triggering. The green Trigger light is always on and none of the triggering controls work and have a free running sweep. So that's the next issue to track down.

[Specmaster]

Progress on the 485....

The fixed intensity issue was my fault. I forgot to reconnect R1567 when I was troubleshooting the +15V short. 



The scope now has a sharp trace. I verified the PSU voltages and they are in spec although I will eventually recap it. Many of the controls are gummed up and dirty so deoxit to the rescue. I burning smell upon first power up has not returned and I don't know what it was. I'm sure sooner or later it will rear it's ugly head.

New issue. Absolutely no triggering. The green Trigger light is always on and none of the triggering controls work and have a free running sweep. So that's the next issue to track down.

Looks like the Tek gods are really determined to test you to the limit 

[BU508A]

When I'm fiddling around with electronics (with the tongue at the right angle), my prefered music in the background is (in no particular order)
- Pink Floyd
- The Alan Parsons Project (from "Tales of mystery and imagination" up to "Vulture Culture")
- Kraftwerk
- Jean Michel Jarre (occasionly)
- Barclay James Harvest (preferred "Eyes of the universe")
- Jeff Wayne's "War of the worlds"
- Ganymed "Future wolrds"
- to be continued ...