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91
Metrology / Re: LM399AH at 5v?
« Last post by alex-sh on Yesterday at 08:11:40 pm »
The tempco itself of the 50k 10turn pot is not important imho, the matching tempco between the 2 portions of the pot does..
What could be a matching tempco of such A and B parts of the pot?

The datasheet does not say. They just say about tempco for the pot.
This is prudent to assume that it would be not less than pot's tempco.

http://www.vishaypg.com/docs/63056/12801285.pdf
92
Beginners / Re: DS3231 is not accurate as it should be
« Last post by imo on Yesterday at 08:09:23 pm »
https://hackaday.com/2017/08/09/get-inside-a-tcxo-clock-chip/
https://blog.heypete.com/2017/07/29/a-look-inside-the-ds3231-real-time-clock/
And yes, it is the greed of our lovely distributors..
I don't think it's greed so much as it is the cost of overhead.
A good topic for a separate thread. It is the greed and cartels..
93
Manufacturing & Assembly / Re: 3D printer’s heat bed fabrication
« Last post by Mechatrommer on Yesterday at 08:08:36 pm »
right! attached is the heat bed i built a while ago. it measures something like 40 x 60 cm. CAD assisted copper wires formation inside fiber glass stacked between 2 tempered glass. since its using copper, its much more efficient than the (busted) 100% efficient solus heater, although it will bend a bit during heating up. and no, this one is not for sale (hence not a spam) even if its advertised as an upgraded version of solus heater (you'll cry for the shipping cost)  :-DD
94
General Chat / Re: Fake $9 Chinese Intel 8087 chip from eBay
« Last post by CJay on Yesterday at 08:08:19 pm »
This applies to *ALL* potential problems with vendors on eBay, not just Chinese ones (who are, in general really quite good IME)


Sometimes the *only* way to get a seller to talk to you about resolving a problem is to leave negative feedback but I'd always try and resolve an issue before the negative.

I've learned by experience that the best option is to open a case with eBay ASAP before any of the weasel words or 'well return it and we'll refund/replace/whatever' offers are made, make it all official and do all your requests via the eBay system.

 I have had more trouble with UK based sellers than Chinese ones. I'm stuck trying to get a return and refund on a not as described piece of gear right now with a seller who lives only ~40 miles from me.
95
Manufacturing & Assembly / Re: Free PCB: [ THIS IS NOT PCB FAB SPAM ]
« Last post by Psi on Yesterday at 08:07:25 pm »
Yeah even the $2 offer from JLC has me worried about it.

The PCB market is getting way too saturated and seams like they are desperate to get costumers. At some point the whole thing is going to break down and result in something similar to the recent "great ceramic capacitor shortage"

I doubt it, some of them will go under/bankrupt and the others will get more business which makes them less likely to go under themselves. It's all self correcting.

For a Great PCB Shortage you'd need to have two factors happening at once.
Like a few of the major PCB companies going under and the demand for PCBs to reduce at the same time.

eg, maybe some new 3D printer tech comes along and suddenly everyone gets the ability to print perfectly solderable copper tracks onto a bare pcb. (ok, maybe that's a bit unlikely, but you get the idea.)
96
I remember I saw a Raytheon A-Si camera core on both ebay and Youtube, which have a curved line of pixels that do seems to be permanently burnt, not only temporarily shifted.
I also have a blurry memory that the owner said the camera was used as a CCTV camera outdoor, then it was burned by the rasing sun in the morning.
I cannot find the source for now...
97
Beginners / Re: DS3231 is not accurate as it should be
« Last post by tooki on Yesterday at 08:05:37 pm »
https://hackaday.com/2017/08/09/get-inside-a-tcxo-clock-chip/
https://blog.heypete.com/2017/07/29/a-look-inside-the-ds3231-real-time-clock/

And yes, it is the greed of our lovely distributors..
I don't think it's greed so much as it is the cost of overhead. Look at Digi-Key: they have over a million SKUs in stock. The warehousing costs for this, and the logistics to get a few units to you, are huge. (This is why the volume discounts become so large, since sending you an entire reel of 5000 takes less effort than counting out and repackaging 3 pieces.)

In contrast, the Chinese eBay sellers typically stock around 1000 SKUs, and their labor costs are trivial. So their overhead is massively lower. Their module suppliers probably buy 100,000 chips at a time, getting huge discounts, and then sell them to a bunch of different eBay vendors.
98
Matches my experience.
The STM32H7 series chips were heavily delayed, and the nucleo boards were (somewhat) hard to get where all the others were easily available. They admitted that the chips had issues and didn't supply you with demo boards as generously as with other STM32 series if you didn't have a particular project.
My guess, the new revision isn't just a bug fixed chip but heavily revised, which is rather unusual. I think their strategy was to keep the amount of the older revision chips in the wild low enough so they can prepare to replace them silently with the new revision if you just ask hard enough rather than provide full support for the older chips. At least that was my experience with a bunch of STM32F7 chips that had the ethernet MAC bug, they've sent us free samples of the fixed revision to replace them on the boards.
99
Test Equipment / Re: Rigol DP832A Software
« Last post by H.O on Yesterday at 08:04:59 pm »
There's not much else to say that hasn't already been said.

The purpose of the USB Host interface is to allow you to put a thumbdrive in the unit and update the firmware, save and load instrument settings etc. It can also be used to connect the optional USB<->GPIB adapter.
The purpose of the USB Device, RS232, Ethernet and GPIB interfaces are to allow you to programmatically control the instrument. Electrically and physically the interfaces are different (obviously) but the commands you use to control the instrument are the same, whichever interface you choose to use.
The purpose of the digital trigger input(s) is to allow you to remotely control the state of the output(s) with a digital signal.
The purpose of the digital trigger output(s) is to allow the instrument to "put out" a digital signal when a certain event occurs (for example when an output goes into CC mode).

ALL this information IS in the manual and in the programming guide.
When it comes to programming/controlling the instrument remotely over USB, GPIB, RS232 or Ethernet you REALLY need to do a bit of reading on the subjects of VISA and SCPI to understand what it's all about.

Here's the manual.
Here's the programming guide.
100
Test Equipment / Re: Test Equipment Anonymous (TEA) group therapy thread
« Last post by tautech on Yesterday at 08:04:11 pm »
@ med
Can you get Simple Green, that stuff can work miracles on some mucks.

I have/use Simple Green all the time. Great stuff.  :-+ But I didn't try it here. Used an ammonia based window cleaner.
Do you think someone has used a solvent on that screen ? Is it smooooth as babies bum or roughened like partially melted by a solvent ?

I hit mine with the vacuum and brush then gave it a soft brush scrub with IPA. Given the vintage of mine it is almost certainly wire. Still not using it as the Graticule's  were a PITA to see.

Currently PC tethered to phone as the Internerd is  :rant: again tonight.
Was yours as grubby as meds ?
His is downright yuck !
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