Test Equipment Anonymous (TEA) group therapy thread

[Carl_Smith]

Another TEA update:

Turns out that the first seller that never shipped the GDM-8251A meter I bought had not had some terrible accident or something that prevented him from shipping my meter.  He just apparently didn't check his eBay account for almost 3 weeks.  He sent me a message yesterday apologizing and saying that his email notifications didn't work and he didn't know he had a sale, and he would ship it out that day.  Told him don't bother, ebay already refunded me and I purchased and received one from another seller.

Today I acquired something else.  A GW Instek GPD-3303S power supply.  I was watching the auction with 35 minutes to spare when I got a phone call.  Later I remembered the auction and hit refresh quick to find 30 seconds left and a bid of somewhere around $125.  I entered a bid of $140 and got instantly auto-outbid.  But eBay gave me a convenient "bid $143" button to click with seconds to spare and I got it for $142.51.  Why that odd amount I don't know.  Forgot about the $29.99 shipping though.     Still probably a good deal.

Spent nearly $1300 on repairs to my SUV today so what's another $172.50.

Now I just need a better function generator...

[Brumby]

I entered a bid of $140 and got instantly auto-outbid.  But eBay gave me a convenient "bid $143" button to click with seconds to spare and I got it for $142.51.  Why that odd amount I don't know.

The reason is one I have actually exercised myself - and you would have lost by the smallest of margins if you did not make that extra bid - and here is why ....

The other bidder put in a 'maximum' bid of $140.01 - specifically to be "just ahead" of anyone who bid a round amount like $140.00.  The previous amount of (let's say it was $125.00) is the result of someone else bidding $122.50 against this $140.01.  EBay's proxy bidding system applies a bid increment which, at that price rangel, is $2.50, giving a proxy bid of $125.00.

When you put up a $140 bid, the eBay system tried to apply another bid increment of $2.50 - but the maximum of the other bidder was $140.01, so the eBay system could only push the winning bid to that.  If you had stopped there, you would have lost by 1 cent.  When you put in $143.00, the eBay system applied the $2.50 bid increment, resulting in you winning for $142.51.

Looks weird on the surface - until you see the tactics bidder use to edge out other bidders.  The best example I had was 3 bidders sniping for a monitor many years ago.  I won it for $162.67 - beating out the runner up by two cents.

[rrinker]

 Bugger, you're the one who outbid me on that one. 
 

 I hadn't seen that new addition ebay made, so much for the tactic of making odd cent bids to block last second attempts. I don't think there's a change ebay has made in the past 10 years that is positive.

[bitseeker]

When it comes in is there a thread or somewhere to show it off display it and get it critiqued?  Or should I make another (oh, no, not another newbie bench thread) thread?

That usually goes in https://www.eevblog.com/forum/chat/whats-your-work-benchlab-look-like-post-some-pictures-of-your-lab/

[Housedad]

Thanks!   I have to show off my TEA party.   

As soon as I can get the dang ripples out of the edges of my new ESD mat.  It came with them and I'm hoping they will flatten out with a couple of days of laying on the table.   

[xrunner]

As soon as I can get the dang ripples out of the edges of my new ESD mat.  It came with them and I'm hoping they will flatten out with a couple of days of laying on the table.

They won't - at least if it's like mine. I need to take a heat gun to it or something ... 

[bitseeker]

Surely placing come boatanchory instruments on it, upside-down, would iron out the wrinkles. If not, that's some wicked rubber.

[xrunner]

Surely placing come boatanchory instruments on it, upside-down, would iron out the wrinkles. If not, that's some wicked rubber.

Dude I've tried that and even rolling the edges in reverse overnight - noting has fazed it.

I don't know how long it's rolled up before shipping but it really has a memory! 

[bitseeker]

Dude! That is some gnarly material. They should put a warning label on it.

[Housedad]

It looks like at some point the ends or the roll got really cold or the center got hot.   Remember that true rubber reacts to cold the opposite of most materials.  It expands when cold and shrinks when exposed to heat.  Maybe I need to keep some heat on the edges for a while.  hair dryer or something.

[SingedFingers]

I've got a blue ESD mat from RS that will not lie flat on any surface. There's just something about the damn things.

I just use cardboard now and zero static protection. Not blown a thing up.

[tggzzz]

I just use cardboard now and zero static protection. Not blown a thing up.

... but how do you know there hasn't been any parametric degredation?

[SingedFingers]

I just use cardboard now and zero static protection. Not blown a thing up.

... but how do you know there hasn't been any parametric degredation?

I don't and I know I don't. I'm accepting this risk this for personal projects. If I was in a professional environment, or working on professional equipment, or on a production line, things are different but on the bench at home prototyping something, I'm not particularly bothered.

I am a risk to the parts through gross negligence in wiring more than static. I've lost count of the number of times I've caused "parametric degradation" on an innocent little 2n3904. What do you mean my beta is now 15 - all I got was a little hot? In the bin with you...

Edit: just to clarify, I spent two years at a defence contractor heel strapped up and with a blue coat of death on so I'm aware of the production realities of such things. It's not a trade off I can be bothered with at home. The cost of a failure is low.

[xrunner]

Anti end curl-uppy prevention strategy items ...

[ManateeMafia]

I wonder if 15-20 minutes outside on a sunny day would help it relax and lay flat?

[SeanB]

How about some carpet edging on each end, and stretch it really tight between them. Otherwise a judicious application of a few staples into the worktop should suffice, or a can of 3M spray adhesive and a sandbag overnight to keep pressure on there.

[Cubdriver]

I put matting down on some non-ESD benches at work, and held it in place using double-sided carpet tape around the perimeter of the benchtop.  It's worked well for several years now.

-Pat

[Housedad]

Yes it sucks.  This is still how it looks after nearly 48 hours of laying on the table.  I'm not happy with the way it turned out especially for $60 plus 20 shipping.

[tggzzz]

I just use cardboard now and zero static protection. Not blown a thing up.

... but how do you know there hasn't been any parametric degredation?

I don't and I know I don't. I'm accepting this risk this for personal projects. If I was in a professional environment, or working on professional equipment, or on a production line, things are different but on the bench at home prototyping something, I'm not particularly bothered.

I am a risk to the parts through gross negligence in wiring more than static. I've lost count of the number of times I've caused "parametric degradation" on an innocent little 2n3904. What do you mean my beta is now 15 - all I got was a little hot? In the bin with you...

Edit: just to clarify, I spent two years at a defence contractor heel strapped up and with a blue coat of death on so I'm aware of the production realities of such things. It's not a trade off I can be bothered with at home. The cost of a failure is low.

All very reasonable

My pet "parameter degradation" hate involves suspect RF cables that are hung back on the rack; they should be Widlarised with extreme prejudice.

OTOH I've seen companies that were happy to production test CMOS circuits by shorting outputs to ground.

[rrinker]

 I got my mat from a seller that was recommended in the "What does your workbench look like" thread and it has settled in pretty flat with no "help" other than rolling it up backwards for a short time and then setting equipment on it. The back edge still curls a bit but that's because the whole thing is maybe 1/2 to 3/4" too wide so it interferes with the verticals that support my shelf. Not worth trying to cut the nice straight factory edge. Nothing other than what I'm working on holds it along the front, along the back though from left to right it has my fume extractor (when not being used), power strip (large rectangular Tripp-Lite one with the noise filter and remote switch), and soldering station somewhat anchoring it in place. It did take a while to settle down flat but it will.

 I went all out on this bench and got the mat, and it also came with a 2-socket box to plug in wrist straps which I mounted under the left corner of the bench. I all the years before this, I have never damaged a component such that it wouldn't work. I suspect also no partial damage, based on the evidence of my very first computer, built when I was 12 will all CMOS  components, even the CPU (RCA 1802) and I had NO clue about ESD damage back then. I think the most I did was touch something metal before starting to pick up and install the chips. That machine still works today - even the monster Sprague cap int he power supply isn't bulged or leaky (though I suppose I ought to check the ESR).

 Besides, you need a proper table covering for a TEA party.

[AF6LJ]

Yes it sucks.  This is still how it looks after nearly 48 hours of laying on the table.  I'm not happy with the way it turned out especially for $60 plus 20 shipping.

In the old days a hair dryer and a couple of phone books would flatten that out.

[Housedad]

If it was plastic, yes.   But being rubber, it needs to be completely heated to over 200 degree F, put under tension to stretch it slightly, and let cool while tension continues.   This thing is buggered.

[AF6LJ]

If it was plastic, yes.   But being rubber, it needs to be completely heated to over 200 degree F, put under tension to stretch it slightly, and let cool while tension continues.   This thing is buggered.

I guess that just means a bigger heat gun, a gig made from plywood (or MDF or OSB take your pick) and and you are on the road.

I was lucky my six foot by three foot 3M mat only cost me some labor, a friend has three or four more of these.

[tggzzz]

If it was plastic, yes.   But being rubber, it needs to be completely heated to over 200 degree F, put under tension to stretch it slightly, and let cool while tension continues.   This thing is buggered.

If you haven't got anything to lose, hang it up, weights on the other end, and play a paintstripping hot air gun over it. Those things can melt the solder inside 15mm domestic plumbing joints, so that ought to be hot enough!

[bitseeker]

Anti end curl-uppy prevention strategy items ...

Hey, no getting all technical on us now.