Test Equipment Anonymous (TEA) group therapy thread

[bd139]

LM337 is even more vicious. Marginally stable on a good day and the pins are different to the 317. Guess how I discovered the latter 

Edit: Oh random thought today. I am giving up on hamfests now. Possibly permanently. I'm just about done with the whole ebay bouncing business and want to get on with making stuff now. That does not preclude my exit from the glorious TEA thread for I will still look on ebay 

[med6753]

This supply nearly 30 years old. Designed and built by yours truly. It has 3 - LM317's and 1- LM337. And it's in daily operation powering scanner accessories. Never an issue.

 

[mansaxel]

LM337 is even more vicious. Marginally stable on a good day and the pins are different to the 317. Guess how I discovered the latter 

And just the other day I ogled a diy PSU design using both, 317 and 337. Somehow, I thought they'd been a tad gung-ho about it; they had based it on a 2x24V transformer, relying on the peak voltage post-rectifier to get to 2x30.  Not very confidence-inspiring.

I could really do with a single 50+V PSU; does not have to be much current (probably OK with 500mA). But, cheap is good ;-) Anyone got anything they'd part with? 

[McBryce]

I avoid games of chance where possible

Just seen my next car on ebay: https://www.ebay.co.uk/itm/313016881099

The creator seems to be misinformed on the heat resistance of plastic rear lights. I think I would have extended that aluminium cladding a tad further back.

McBryce.

[bd139]

LM337 is even more vicious. Marginally stable on a good day and the pins are different to the 317. Guess how I discovered the latter 

And just the other day I ogled a diy PSU design using both, 317 and 337. Somehow, I thought they'd been a tad gung-ho about it; they had based it on a 2x24V transformer, relying on the peak voltage post-rectifier to get to 2x30.  Not very confidence-inspiring.

I could really do with a single 50+V PSU; does not have to be much current (probably OK with 500mA). But, cheap is good ;-) Anyone got anything they'd part with? 

Ugh I bet that got a bit lumpy with some load. Mains variation + transformer load + diode drops + capacitor charge drop = headache.

Any good? https://www.ebay.co.uk/itm/183713821017

[Wolfgang]

LM337 is even more vicious. Marginally stable on a good day and the pins are different to the 317. Guess how I discovered the latter 

Edit: Oh random thought today. I am giving up on hamfests now. Possibly permanently. I'm just about done with the whole ebay bouncing business and want to get on with making stuff now. That does not preclude my exit from the glorious TEA thread for I will still look on ebay 

Same to me. In my case it was especially difficult to discover because the TO-92 version exploded so the crime scene was empty. 

[med6753]

Freaking engineers.  Don't you guys ever look at the data sheets? 

[mansaxel]

I could really do with a single 50+V PSU; does not have to be much current (probably OK with 500mA). But, cheap is good ;-) Anyone got anything they'd part with? 

Ugh I bet that got a bit lumpy with some load. Mains variation + transformer load + diode drops + capacitor charge drop = headache.

Any good? https://www.ebay.co.uk/itm/183713821017

That would fit the bill, yes. Bit expensive shipping, though. (56 bleeping quids...)

[bd139]

Freaking engineers.  Don't you guys ever look at the data sheets? 

LOL who do you think we are? The SOA is better determined experimentally. Can't go trusting those datasheets! 

That would fit the bill, yes. Bit expensive shipping, though. (56 bleeping quids...)

Ouch!

[AVGresponding]

Hmmph, just got around to powering up the HP 1120A. I now know 2 things.

My Black Star Jupiter sig gen is useless for square waves above a few hundred kHz, and wow, this thing sucks power like a damn immersion heater!

Around 60mA on the -12.6V rail, and just short of 90mA on the +15V rail. The probulator actually gets warm to the touch!

Seems like a lot of power to me, though there were no bad smells or emissions of magic smoke.

Sooo... top of my shopping list is now a decent AWG   

[bd139]

Don't buy a Rigol one 

[Cerebus]

Ah, yes, driving that is a game of chance like the 1995 Darwin Award
https://darwinawards.com/darwin/darwin1995-04.html
(yes i know that and that, but I'm not going to let that get in the way of a fond memory )

One should never let the facts get in the way of a good story.

[tggzzz]

Looks like my new toy escaped just in time...

"Ramco Ltd to temporarily close. Following the Government's recent announcement we are closing the doors until further notice. No further collections or deliveries will be accepted. Any equipment you have either purchased or placed into one of our auctions will remain in our care until this National Emergency has passed and we can reopen."

Not unreasonable

[AVGresponding]

Hadn't heard Rigol were that bad.

I certainly won't be buying a Feeltech...

I'll just have to be patient and wait to get lucky on ebay, since I can't afford anything remotely new from a decent brand.

[Cerebus]

LM337... the pins are different to the 317. Guess how I discovered the latter 

I've discovered that the hard way too, fortunately I figured it out before the magic smoke escaped. Although there's only about £0.10 worth of magic smoke in an LM337 its still nice to not have to replace the only one you had to hand at the time. (Just checked, it's actually £0.60-0.70 worth of magic smoke, but the principle still applies.)

[daveyk]

Hello mnem,

I recently purchased an EDS-88A.  It seems pretty nice and since it is for my business, it is a tax deduction.  I didn't mind the cost and it seems real nice.  I see you also link to the ESR70 too.  I may order one of those as these type of devices fascinates me, for what ever reason - simple minds are easily amused LOL.

Do you have much experience with the ESR70? It looks good.  I find them for anywhere from $95 (shipping from the US) to $140 (also shipping from the US).  I don't know why there would be a $50 difference in where you purchase from.  Of course, my brain says buy the cheapest; my gut says to investigate further.

The EDS system machines rely on precise gold plated probe.  The other just have regular tin plated clips.  Perhaps this is why my experience with ESR machines has been so-so, and actual replacement is the best cap test.

I have an Agilent 4362B and the Kelvin Clip assembly (!!!).  I found any cheap ESR meter so much easier to use and rarely fire up the Agilent 4362B.  Perhaps it is the Kevin 16089C only using tin plated clips?  We are talking very low resistance when measuring ESR.

I have also ordered everything needed (Case, PCB, parts kit, and gold plated probe) to build the EDS-89A Short finder.  Do you have any experience with it?  There is a youtube video showing the use of the older EDS-88A short finder.  It seems amazing.   You get a short anywhere on a power rail, it can be impossible to find the short without cutting traces and these days with 6 layer boards, that is mostly impossible.  We are talking milli-ohms, or less, in trying to track down shorts.  So, I am anxious to try that out too.

Take care and stay safe from the Covid-19 virus.

Dave

[Cerebus]

Looks like my new toy escaped just in time...

"Ramco Ltd to temporarily close. Following the Government's recent announcement we are closing the doors until further notice. No further collections or deliveries will be accepted. Any equipment you have either purchased or placed into one of our auctions will remain in our care until this National Emergency has passed and we can reopen."

Not unreasonable

Not unreasonable until you find the buggers have charged you storage fees.

[bd139]

Hadn't heard Rigol were that bad.

I certainly won't be buying a Feeltech...

I'll just have to be patient and wait to get lucky on ebay, since I can't afford anything remotely new from a decent brand.

TBH I'm mostly being unfair. The absolute bottom end Rigols are decent quality, just the user interface is a complete ball bag from end to end. They work fine if you can stand some suffering on that.

Also new price is pretty good and you can crack it to two channels and 100MHz as it's exactly the same hardware as their highest end unit: https://www.telonic.co.uk/Rigol-DG811-Waveform-Generator-p/dg811.htm

I only bought mine because it was crackable 

[tggzzz]

Looks like my new toy escaped just in time...

"Ramco Ltd to temporarily close. Following the Government's recent announcement we are closing the doors until further notice. No further collections or deliveries will be accepted. Any equipment you have either purchased or placed into one of our auctions will remain in our care until this National Emergency has passed and we can reopen."

Not unreasonable

Not unreasonable until you find the buggers have charged you storage fees.

"I came to pick up the X but there were none of your staff to give it to me".

Nonetheless I'm glad Equipnet haven't got back to me w.r.t. my very lowball bid. Before placing the bid I asked them about what would happen if there was a CV lockdown; they didn't know.

[mnementh]

...And I agree with the dragon. Their tracking is utter bullshit. 

*passes out from the shock*

FFS!   was away for a short time and return to find all the brits have turned into "statler and waldorf" from the muppet show!

and the dragon is now "the voice of reason".   screw this..........am going back down into my "fortress of solitude" and work some more on reducing noise in my 10 Ghz yig oscillator. 

(actually managed to fry an lm317 yesterday.  did not expect it to fail short!)   ps  fortunately med is a never changing rock of stability.  (a blue assed NY bastard bitchin' about snow and the postal system).

LM317 is one of those devices with a lot of lore around it. Some of my favourites which I find terribly funny:

1. I can make a 1.2-30V regulator that will kick out an amp with one. Proceeds to then run it with a 40V input and 3.3V output with an inch across heatsink on it trying to absorb 25 watts or so. BOOM!
2. They automatically current limit if they get hot. BOOM!
3. They make a good charger IC for SLA batteries. Line power goes down, missing protection diodes. BOOM!
4. They are universally stable. Runs it with 30 foot of inductors between the regulator and load. BOOM!
5. They are short circuit proo.....BOOM!
6. You can strap a CC circuit behind a CV circuit and make a bench power supply. Oh it's oscillating like fuck. BOOM!
7. It fails open (a thing you found out isn't true). Nope the pass transistor goes C-E short almost always and dumps the entire input voltage across the load.

If you value anything that any linear regulator is connected to regardless of type or vendor or even if it's a commercial power supply from a big brand, you stick a crowbar in circuit.

LM317 is little more than a LM78xx deliberately designed with a floating "ground" reference rather than accidentally.    Yes, it is MORE; but VERY little more.   I remember an article online where someone used a feedback loop to create an audio oscillator from one. Meh... we all get bored from time to time. 

Blah, enforced staying-at-home and seeing other people's workbenches has finally shamed/motivated me to clearing my own a bit.
Currently down to an approximate 2" (50mm) layer...  soon I'll be able to see the actual bench surface!

I know from experience it's that last 1/2 inch that is the most time-consuming (provided you don't just sweep it all into the dustbin in disgust); putting all those tiny screws and nuts and short-legged-but-still-good resistors, diodes & other semiconductors where they belong is a chore that turns into a God-given QUEST. You eventually tough it out because you can't bear to admit you've made a mess that even you cannot clean up.

Freaking engineers.  Don't you guys ever look at the data sheets? 

Only technicians look at datasheets.   

mnem
Permanence is fugitive.

[URI]

Moved a few weeks ago, now I've got some extra space so the home lab gets to stretch its legs.

I'm a little late, but:
You've got a great bench there!   
I wish I had so much space and wouldn't have to use the high ceiling in my apartment.
There's only one thing better than bench space: even more bench space.   

[Specmaster]

I avoid games of chance where possible

Just seen my next car on ebay: https://www.ebay.co.uk/itm/313016881099

Great for burnouts or burning down a neighbours fence, or even in the Top Gear style destroying a caravan but utter shit and lugging home loads of TEA or Ham items 

[bd139]

Mmmm caravan. Now that's a good idea.

Just had to fettle with the 3d printer properly for the first time. New nozzle, levelling and clean the bed. Printing a custom enclosure for my pulse oximeter.

[Specmaster]

So where is the Fluke 8505A I purchased over a week ago? You'll have to ask USPS. Because it's taken nearly 6 days for it to travel approx. 120 miles. It shipped then disappeared into a black hole for nearly 4 days before showing up in Jersey City. Then it whizzed right by my location to spend a day in Springfield. Now it's left Springfield and should be at my local post office today (Tuesday). But hold on...the roads around here suck right now. North of me got blasted with snow. Upwards of a foot of the white stuff. And that's where Springfield is located. 

 

Yep, sometimes you have wonder the sheer logic of these carriers. It will possibly wind its way back from Springfield to a dept nearer to you for final delivery  Thats always assuming of course they can keep Homer Simpson away from it otherwise it could end up in Mo's Tavern 

[URI]

Freaking engineers.  Don't you guys ever look at the data sheets? 

LOL who do you think we are? The SOA is better determined experimentally. Can't go trusting those datasheets! 

..may be subject to change without further notice..     

Datasheets are not binding in a legal sense.   
You get most fun of it when you're trying to build a logical network into a CPLD and the manufacturer changed timing properties and parts of the structure/paths. In some sense he improved it but according to the current datasheet I worked with, it was partially out of spec, resulting in a hard to trigger (and hard to observe) race condition that should not even have existed but did.   
Ok, I learned to improve my design to be not dependent on timing boundary values of the underlying hardware..
Was a student then and never used that know-how again.