50G ohm Retirement Fund - Page 1
Forum section: electronics / general

author: pguerra75
author_rank: Newbie
timestamp: March 14, 2017, 07:50:28 pm
content: I was recently cleaning up shop in an electronics warehouse and came across an interesting find. A plastic bottle of approx. 26000 loose 50g Ohm 30% resistors (0805) package. I did some research and the cheapest I can find these things is around $2 at volume. So essentially I found $52000 worth of parts that almost no one will want. One can only laugh.Just thought this crowd might enjoy that.

author: alm
author_rank: Super Contributor
timestamp: March 14, 2017, 08:44:43 pm
content: I wonder what kind of PCB cleaning you would need to keep parallel leakage down for such a small package. Put guard traces around the pads? Mill a narrow slot under the resistor?

author: Benta
author_rank: Super Contributor
timestamp: March 14, 2017, 09:31:48 pm
content: QuoteRattling around in a bottle, you can be pretty certain that they are not 50 Gohm anymore.

author: Codebird
author_rank: Regular Contributor
timestamp: March 14, 2017, 09:41:12 pm
content: I can't imagine what anyone would even want with such a part.

author: Benta
author_rank: Super Contributor
timestamp: March 14, 2017, 10:17:49 pm
content: Quote from: Codebird on March 14, 2017, 09:41:12 pmYes, the customer base is limited, to say the least. Not where I'd put my retirement fund.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: March 14, 2017, 10:36:34 pm
content: Pictures?

author: jpanhalt
author_rank: Super Contributor
timestamp: March 14, 2017, 11:25:11 pm
content: List them on eBay as "vintage." What have you got to lose?

author: TerraHertz
author_rank: Super Contributor
timestamp: March 14, 2017, 11:43:19 pm
content: Huh, that's amusing. Since I need some 10G and 20G surface mount resistors.Too bad paralleling them up probably won't work so well, since the surface leakage would be additive, cleaning more difficult, and greater overall parasitic capacitance.For why I need some, seehttps://www.eevblog.com/forum/repair/restoring-a-mass-spectrometer-maybe/Anyway how much for about 100 of them? (And are you aware you shouldn't handle them with bare fingers?)

author: pguerra75
author_rank: Newbie
timestamp: March 15, 2017, 12:24:58 am
content: QuoteNot gonna charge anyone do to the fact I don't know their history. PM me your address and I'll ship them over, and yes I am awareQuoteQuoteHaha, I should list them individually, haha.

author: pguerra75
author_rank: Newbie
timestamp: March 15, 2017, 12:27:16 am
content: QuoteNor can I but I am a bit of an impostor EE.

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 15, 2017, 01:58:27 am
content: Quote from: pguerra75 on March 14, 2017, 07:50:28 pmHow did you figure out the quantity? Weight?

author: pguerra75
author_rank: Newbie
timestamp: March 15, 2017, 02:33:28 am
content: QuoteI had a local jewler weigh a sample of 100 and then the lot.

author: MarkS
author_rank: Unknown
timestamp: March 15, 2017, 02:54:12 am
content: 50G Ohm? 50 giga-Ohm?

author: Bryan
author_rank: Frequent Contributor
timestamp: March 15, 2017, 05:34:09 am
content: For what application what would a 50Gohm resistor be used for?

author: boffin
author_rank: Unknown
timestamp: March 15, 2017, 06:26:33 am
content: You sure they're not caps?I say that due to the colour, sort of a yellowish which is pretty common with ceramic caps.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: March 15, 2017, 08:14:20 am
content: If you have nothing better to do, hook up say 100 of them in parallel and see if it checks out to about 500M, which would be a more easily measurable value. Or hook up a few of them in parallel and see if they measure as a capacitors I guess. I have a hard time seeing where something like a 50G ohm resistor in such a small package would be useful. Maybe in something that is potted, but then again just the resin would probably contribute a not insignificant stray resistance. So hmm...Would love to see a "teardown" of it though. Maybe polishing one layer at a time off of it to reveal its internal structure. Maybe send the whole bag, or a carefully selected sample, to mikeselectricstuff?

author: AndyC_772
author_rank: Super Contributor
timestamp: March 15, 2017, 09:25:50 am
content: Factory rejects. They were supposed to be 10k, but someone forgot to apply the metal film and just left the ceramic substrate.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: March 15, 2017, 09:31:49 am
content: Quote from: Bryan on March 15, 2017, 05:34:09 amElectrometers. At work I routinely use 20G and 100G resistors and plan to use SMD parts of these values in a near future. The application in my case is Quadrupole Mass Spectrometry. Similar electrometers are used in many other applications where very small charges/currents have to be measured or sensed. The current noise level is reduced with the increase in the resistor value, so larger the value, lower the noise (but slower the response due to a parasitic capacitance). 20G resistor has about 1fA RMS self-noise in 1Hz BW. 50G resistor - about 0.6fA.I can also add that it is perfectly possible to use SMD parts with these values. If somebody would like to know the details, than theADA4530-1datasheet, evaluation board description and AN-1373 application note can provide a good starting point.CheersAlex

author: tszaboo
author_rank: Super Contributor
timestamp: March 15, 2017, 09:36:28 am
content: Quote from: boffin on March 15, 2017, 06:26:33 amPreatty much, what I would have said. 50Gohm on a pcb in a 0805 package is a part not soldered in...

author: alm
author_rank: Super Contributor
timestamp: March 15, 2017, 09:43:19 am
content: Well, 50 GOhm resistorsdo exist in 0805(up to 100 GOhm in that series). Make sure you do not exceed that 1/8 W power rating.

author: tggzzz
author_rank: Super Contributor
timestamp: March 15, 2017, 10:56:28 am
content: Quote from: alm on March 15, 2017, 09:43:19 am... especially when staying within the max voltage rating!

author: pguerra75
author_rank: Newbie
timestamp: March 15, 2017, 05:17:09 pm
content: QuoteYup, verified it all with test equipment.

author: pguerra75
author_rank: Newbie
timestamp: March 15, 2017, 06:18:00 pm
content: Just head an Idea, who things I should glitter bomb Dave with 26k SMD resistors?

author: rsjsouza
author_rank: Super Contributor
timestamp: March 15, 2017, 06:46:02 pm
content: pguerra75, if it is not inconvenient for you I would have some use for a portion of these resistors. I sent you a PM yesterday.

author: Cerebus
author_rank: Super Contributor
timestamp: March 15, 2017, 07:29:24 pm
content: Quote from: Bryan on March 15, 2017, 05:34:09 amFeedback resistor in a transconductance amplifier for measuring nano/picoamps. One of these would give you 0-5V out for an input current of 0-100 pA.

author: TheSteve
author_rank: Unknown
timestamp: March 15, 2017, 07:35:14 pm
content: There does seem to some interest - why not list them for sale in the buy/sell section. Sell them in lots of 50 or 100 or something.

author: Tom45
author_rank: Frequent Contributor
timestamp: March 15, 2017, 07:39:22 pm
content: Quote from: alm on March 15, 2017, 09:43:19 am79 KV is needed to hit 1/8 W power dissipation. I wonder why they even bother with a maximum power specification for these.

author: Red Squirrel
author_rank: Super Contributor
timestamp: March 15, 2017, 07:40:09 pm
content: How do they react to heat, I wonder if they are more meant for less conventional use of resistors such as very sensitive sensory applications?

author: Cerebus
author_rank: Super Contributor
timestamp: March 15, 2017, 08:52:05 pm
content: Quote from: Red Squirrel on March 15, 2017, 07:40:09 pmUsually terribly. Typical tempco for this kind of resistor is in the 1000ppm region, worse than won-hung-lo SMD resistors in more 'normal' values at typically 100 - 200ppm. Note the 30% tolerance. These get used in the kind of instruments that you calibrate before every reading and take the reading quickly before the instrument drifts too much. It's no accident that picoammeters come with accuracies on the order of 0.3% when comparable voltmeters have accuracies 100 times better.

author: ocw
author_rank: Regular Contributor
timestamp: March 15, 2017, 11:15:32 pm
content: I just received four TE Connectivity RH73X2A50GNTN 50G ohm 30% 0805 resistors which were ordered from Mouser. Attached is a picture of them. I don't know how many other 50G 30% 0805 resistors are being made, but the pictured large bag does not contain TE's version. I included an Ohmite MOX-1125-23-4008J 40G resistor for a size comparison.I measured the four resistors as 37.1G (-25.8%), 38.0G (-24%), 45.8G (-8.4%) and 54.9G (+9.8%). Those measurements were made using my Keithley 610C electrometer. I'll probably later measure their values using my homemade meter using a ADA4530-1. The capacitance of the resistors were measured to be about 0.61 pF for each of them.I'd recommend checking the capacitance of those components in the bag. I suspect that they will measure significantly above 1 pF and that you have ceramic capacitors which have a leakage around 50G ohm. You will need to find another source for your retirement fund.

author: Zero999
author_rank: Super Contributor
timestamp: March 16, 2017, 06:30:03 pm
content: Quote from: Cerebus on March 15, 2017, 07:29:24 pmNot very accurate though, as the resistor is 30% tolerance.

author: Dave
author_rank: Super Contributor
timestamp: March 17, 2017, 08:41:58 am
content: Quote from: Cerebus on March 15, 2017, 07:29:24 pmYou're thinking of transimpedance amplifiers. Transconductance amps are voltage in, current out - the exact opposite.

author: Cerebus
author_rank: Super Contributor
timestamp: March 17, 2017, 05:01:43 pm
content: Quote from: Dave on March 17, 2017, 08:41:58 amWhat I actually meant to say was transresistance amplifier but for some reason I seem to regularly get a brainfart with 'trans-x amplifiers' and use the wrong term at least 50% of the time. The only time I reliably get it right is when I mean transconductance I do actually write transconductance.

author: amspire
author_rank: Super Contributor
timestamp: March 18, 2017, 03:11:36 am
content: One of the things you could do with these is to make a High Resistance transfer standard similar on configuration to these:http://www.ietlabs.com/esi-sr1010-resistance-transfer-standard.htmlSelect sets of 5 resistors for parallel use so you end up with 10 or 12 10G resistors that match to better then 1%.Many DVM's can measure up to 1G. This transfer standard can give you 9G and 100G of known values to 0.01%. All it needs is short term stability. The actual resistance values are not very important.Also if you select resistors to give you 10 100G resistors within 1%, you can transfer 10G to 1000G. Not sure who needs it, but you can do it.I am planning something like this with 100M resistors and with cheap reed relays to do the shorting and un-shorting so I can calibrate 100M and 1G ohms ranges of multimeters from the 1M range. Just have to make cards with small magnets glued on to short the relays I want for a particular type of transfer.The only catch is if these resistors end up having a big voltage coefficient, then they are not much use for this.

author: MartinKantola
author_rank: Newbie
timestamp: May 25, 2021, 04:53:38 pm
content: It's been a long time, but I'm interested in those...Martin

author: floobydust
author_rank: Super Contributor
timestamp: May 25, 2021, 08:00:13 pm
content: wtf these aren't in a reel, who buys SMT in bulk packaging?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 25, 2021, 08:54:01 pm
content: Quote from: floobydust on May 25, 2021, 08:00:13 pmEx-buyers. The existence of this lot is proof that at least one entity didn't use them. The buyer probably got a killer price on them. Maybe tthirty percent off of the reel packaged parts. And couldn't understand why his next paycheck was printed on pink paper.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 25, 2021, 09:04:34 pm
content: Quote from: floobydust on May 25, 2021, 08:00:13 pmThere are special feeders for bulk part. However this is more for the more common (and not so delicate) ones, like 0 ohms, 47 ohms or 100 nF caps.