Restoring a Mass Spectrometer - maybe - Page 1
Forum section: electronics / repair

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2017, 01:22:28 pm
content: Recently I scored a mostly complete Mass Spectrometer / Residual Gas Analyzer. Which *might* be possible to restore to working order, and would be very useful for a project of mine. The only thing actually missing was the rotary backing pump and plumbing. The turbomolecular pump was still there.But I didn't want to start a thread in repair until it seemed fairly certain it could be restored. Which isn't clear yet.However an unexpected problem appeared, where you guys may be able to help me.The system is a Model: DCQ300RF, made by Anglo Scientific Instruments.The OS on the control PC is Win98SE, to give an idea of the vintage.Google finds:http://www.angloscientificinstruments.com/Telephone: +44 (0)1805 625 205Postal addressAnglo Scientific Instruments,3, Devon Units, Hatchmoor Industrial Estate,Torrington, Devon. EX38 7HP. UK.email: angloscientific@live.co.ukThe web site exists, though it's kind of minimalist and the most recent date I can find anywhere on it is from 2011.Then, while evaluating the condition of a critical PCB (high input impedance amplifier for the quadrupole sensor) I found one of the key parts is broken. A tiny resistor... which unfortunately is the DC feedback path to the input FET amplifier summing point. A SMD resistor, but suspended in free space on two wires to avoid PCB surface leakage. The wires had been left under tension, broke the solder contact off one end of the resistor. It will be a very high value, and is unmarked. My HP 3456A says it's open circuit, ie > 1 G-ohm. Most likely the resistor is actually broken and open circuit. I have no way to even guesstimate the correct value. It's the bit that sets the loop gain for the tiny current of ions reaching the central sensor electrode in a vacuum. Could have been almost *any* other part in the system and I'd have been able to work out a probable value. But not this one.So I tried emailing angloscientific@live.co.ukAsking what is the correct value for that R7. (Also if schematics and calibration procedure are available, but I never had much hope of that.)They don't respond. At all. Not even a "sorry, no." (Edit: 20170202: received a response. Still in progress.)My question here is, can any forum member in England, please find out if that company still actually exists, and will respond to anything. They appear to have been quite a small operation. Maybe they just closed down recently, and the web site is still up? Or they are still on Christmas holiday or something.The arrow in the pic indicates the stress-failed solder joint. After removing the wire it looks like there is still metalization on that end of the resistor, but I can't measure any value.They should have used a very fine, soft wire for one side of the resistor.The tall teflon post is actually a feedthrough to the sense pin of the guadrupole unit. The round IC is an AD549.

author: CJay
author_rank: Super Contributor
timestamp: February 01, 2017, 01:43:51 pm
content: Companies house don't have an entry for Anglo Scientific Instruments and their phone number is dead, they do list an Anglo Scientific in Hertfordshire thoughhttps://beta.companieshouse.gov.uk/company/03914022

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2017, 02:01:53 pm
content: Quote from: CJay on February 01, 2017, 01:43:51 pmThanks!Oh oh.https://beta.companieshouse.gov.uk/company/03914022/officerssuggests a company that just went under.Some chiefs still on board, others and all the indians resigned. 'Indians', bearing in mind one of them lives in a castle.Not an email address to be seen.Bah. My luck, probably somewhere in Devon someone recently threw boxes of schematics and spare parts for this system into a dumpster.

author: samofab
author_rank: Regular Contributor
timestamp: February 01, 2017, 02:09:13 pm
content: SMD resistors over 1Gohm do exist. And if the resistors was suspended away from PCB it's likely that it is a very high value. Try to measure it with something that goes up to 10Gohm.

author: CJay
author_rank: Super Contributor
timestamp: February 01, 2017, 02:22:34 pm
content: Quote from: TerraHertz on February 01, 2017, 02:01:53 pmDoesn't look too bad to me, none of those resignations are particularly recent and the accounts look fairly healthy and up to date don't they?What I would question is if they are the same company. Would be worth a phone call if I can find a number.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2017, 02:31:16 pm
content: Quote from: samofab on February 01, 2017, 02:09:13 pmI don't have anything that can do that. Oh wait... nanovoltmeter. Hmm.I've yet to look at the end of the resistor with a microscope. Fingers crossed it will be just the solder that fractured, leaving the hard metalization on the alumina. In which case I'll just solder on a fine wire, clean the resistor well, and try it in operation.With the sliiiight complication of having to get the high vacuum system working before that will be possible.At least I have some nice test gases.http://everist.org/spacejunk/sell/helium-3.htmI had posted a few random pics elsewhere:https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1121700/#msg1121700https://www.eevblog.com/forum/testgear/does-anyone-know-how-to-get-the-handles-off-this-case/But will do a more complete tale here later.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2017, 03:02:19 pm
content: Quote from: CJay on February 01, 2017, 02:22:34 pmThe last one was for 2015. Maybe 2016 is still coming.Mysterious to me. Looking through the docs there, I can't find anything that even hints at what that company does.Debtors 344,539, but only 250 in bank? How do they pay wages?QuoteMight be completely unrelated. But strange to have two different companies existing for a long while with the same name.

author: CJay
author_rank: Super Contributor
timestamp: February 01, 2017, 03:18:15 pm
content: Quote from: TerraHertz on February 01, 2017, 03:02:19 pmWell 2015 was filed October 2016, so I'd not expect 2016/17 until October this year.It's a bit odd that they don't seem to exist according to Google and yeah, info on what they do is sparse, didn't have time to dig more though. Happy to give them a call if you find a number though.Lots of companies are debt financed, they use the bank's money. Can't last forever and it's not ideal but...QuoteMight be completely unrelated. But strange to have two different companies existing for a long while with the same name.It's not not that uncommon, one is Anglo Scientific, the other is Anglo Scientific Instruments, there are lots of companies with almost identical names.If there's a company reg number on the Devon company web site you could track them that way through companies house and that'd give you the definitive status of ASI but that's not necessarily going to tell you if they were bought out, liquidated and re-emerged from the ashes a day later etc.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: February 01, 2017, 04:35:09 pm
content: Hmm, I work for a company that makes RGAs and very familiar with this kind of circuitry. Most likely the resistor is 20Gohm (my current company is apparently distantly related to the Anglo Scientific Instruments - both originated from the same company long time ago, so the electrometer circuit for their and some of our old RGAs were most likely designed by the same person). I am pretty sure that you won't be able to restore the broken SMD part. Check Farnell for suitable replacements, these are available and not expensive (unlike better through-hole ones). Main problem with an SMD part would be to keep it clean, you need to solder the (preferably much thinner) wires to it, then wash the resistor thoroughly with IPA, dry it in an oven at 60-70C for few hours and only after that carefully solder it on the board, with minimum solder and flux on the Teflon support. There is a slight chance I might find some more info on the unit you have, PM me if you wish.CheersAlex

author: TerraHertz
author_rank: Super Contributor
timestamp: February 02, 2017, 01:02:19 am
content: Update: I received an email reply from the angloscientific email addess, with some information and a schematic of a very similar amplifier module. Conversation in progress, asking their views regarding public discussion of technical details of the system. (Meaning how much I can say here, without annoying them.)Don't know yet if the company is still trading, or whether more tech information may be available.Positive: replacement filaments are still available. Cross off one potential project killer.Also yes, that resistor is 10G or 20G, he's not sure.Alex, thanks. Will do.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 02, 2017, 01:32:46 am
content: I've always been curious about buying equipment like this. How would you know what it was used for, what was ran through it? Seems easy enough to dump the stuff on eBay. I wonder if you contacted some of the parts suppliers if they would even allow you to return them for repairs because of the risk of exposure. Maybe they would have you sign something stating what was ran through it but with surplus ebay, there would be no way to know. Maybe it's a non issue.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 02, 2017, 03:25:43 am
content: Quote from: joeqsmith on February 02, 2017, 01:32:46 amIt definitely is an issue with some such gear. For instance I have a rotary vac pump stashed away, from an ultracentrifuge. The oil itself used in that is highly poisonous (I found out by research after taking the pump, before touching the oil.)In general used vacuum systems should be treated as hazardous.This one though, I'm told was used in some research into coal processing. Pretty innocuous. Also the RGA itself should be quite clean inside, since the only path into it is via a couple of meters of fine stainless capillary and two very fine needle valves in series. This is about as good as it gets.QuoteWell, not a problem for me, since ebay vacuum gear is usually too expensive for my micro-budget anyway.This unit was effectively a dumpster find. Free.The missing rotary pump is not a problem since I have a few already.There's also no facility for pump-down/up automation and sequencing, so that will have to be added.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 02, 2017, 04:48:18 pm
content: Depending on what you want to do with the mass spec, it might not be such a good idea to use a classical rotary pump. For a clean system and if the turbo pump allows it, an oil free membrane pump might be the better choice.Contamination can be a problem. If you send in things for repair, one usually has to sign paper-works to shown what you have done with it and that there is no hazardous contamination.At the university is was quite a trouble to dispose an old system as it had used Hg diffusion pump and was used with Hg containing stuff.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 03, 2017, 11:07:09 am
content: Quote from: Kleinstein on February 02, 2017, 04:48:18 pmThat's a good point, thanks. Though, I'm constrained to using what I have, since I'm poor.QuoteAs for 'repair', given the costs of commercial repair the rule is, either I repair something myself, or it doesn't get repaired.Speaking of which, one of the three turbomolecular pumps that I was given at the same time as the RGA, is aRIGAKU Model RTP 300 VRC SN: RD0793-05 Date: 1995-6It's the biggest of the three, but has no controller or cable. Water cooled.Has some dirt inside on rotor face. Not adhering, due to oil film. Needs cleaning.Ding on bottom rim - dropped on concrete at some time? Effect on rotor balance unknown, still spins freely.Dim: H: 275mm, Throat: 100mm.Googling, it turns outhttp://www.rigaku.com/enno longer make turbo pumps. Not even listed among their products.Very few mentions to be found. A couple of controllers on ebay:http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xrigaku+rtp300vrc.TRS0&_nkw=rigaku+rtp300vrc&_sacat=0Only the $355 one has the necessary cable. Not to mention the *other* proprietary sockets on the controller.And this system, which contains the same pump and controller:http://www.ebay.com/itm/X-ray-diffractometer-XRD-Rotating-anode-Rigaku-Rotaflex-RU-200B-HBC5-/400567351527?hash=item5d43acb8e7:g:~XUAAOSwYIxYAOg-(Ha ha, someone has pinched the rotary backing pump out of that machine, but that isn't mentioned in the listing.)Given all that, I think I'm unlikely to ever be able to run this pump, even if it works. So, might as well take it apart for fun.But first, just in case, I'll ask here if anyone knows of:- User and or service manuals for the pump and controller?- Any ideas of where I might find a controller, for free or up to $100?

author: Kleinstein
author_rank: Super Contributor
timestamp: February 03, 2017, 12:20:02 pm
content: Getting a controller for the pump could be difficult. Maybe you can get some from Iran, including the stuxnet virus.Even if the rotor is rotating free at low speed, there is still a chance the bearing may need service / oil change.Normally the mass spec should not need a big pump. Small ones (e.g. 40 mm inlet) can get away without water cooling.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 03, 2017, 01:41:17 pm
content: Quote from: Kleinstein on February 03, 2017, 12:20:02 pmHa ha. Actually older TMP controllers tend to be analog; no software at all.QuoteI know. Hence finding a manual is essential too. Oil type, level, procedure, etc. Chances are extremely low.QuoteOh, I should have mentioned. The RGA is not _the_ project. It's a nice addition to the main project. Which _does_ need a large turbo pump. And a rapid pump-down rotary (this:http://everist.org/NobLog/20141212_racked_serendipity.htm) as well as a not-so-big rotary pump for operation.Btw, the mass spec has its own small turbo already. A Varian TV-301 Navigator, complete with controller. Too bad someone beat me to that system and took the backing pump. But no matter.Another part is a Varian 936-60SP He leak detector (which I'd hoped to modify to serve as a mass spectrometer for low atomic number gases, but won't don't need to if the Anglo Scientific one can be restored.)

author: TerraHertz
author_rank: Super Contributor
timestamp: February 05, 2017, 03:09:19 am
content: Since the Anglo Scientific RGA can't function without a working vacuum system, and I have a pile of old vacuum gear to go through and see what works, I may as well turn this into a general 'vacuum stuff progress' thread.And so... *another* thing in that recent score, has been sitting on the bench untouched due to expectation of it being ruined junk, and having too many other things to do. Yesterday I was conducting a vicious cull of pointless junk that was accumulating in the workshop (running out of space) and finally got to that bit of gear.It's a HP 5973 Mass Selective Detector. Google it.http://www.aimanalytical.com/Manuals/5973N%20Inert%20MSD.pdfhardware manualebay, webhttp://www.ebay.com/itm/HP-AGILENT-5973-NETWORK-MASS-SELECTIVE-DETECTOR-/361417325460https://www.gmi-inc.com/agilent-hp-5973-mass-spectrometer.htmlIn use it's supposed to sit next to a HP gas chromatograph, to separate different fractions for analysis in the MSD. But it can work alone too. This one was made in 1999, according to an internal cal label.The reason I expected it to be useless, is it's missing some bits (both hi-vac and backing vacuum pumps), and also had been dumped outside in the rain for a long time - worse than the Anglo Scientific unit.Anyway, regardless of whether there's any chance (probably zero) of getting it working, it's very cool looking.I like the Anglo Scientific one because it's more likely I can maintain and reverse-engineer it due to its simplicity.The HP one is obviously orders of magnitude harder, even though the principles are the same - its still a quadrupole sensor. Also the boards have dust and water trails across them, though at first glance they look like they should be restorable with a good cleaning. Leaving whatever original faults existed, if any. Fingers crossed it just got thrown out because the software is for WinXP. Or the mating chromatograph unit failed, or something.The whole side of the vacuum chamber swings out, with just a couple of thumbscrews and 4 connectors to undo.Someone had left the thumbscrews undone, but the cables were still plugged in. Which was a bit odd. Anyway, no visible damage inside the vacuum chamber, though it was open to the weather for a while via the underneath port to the removed hi-vac pump, and the non-compressed side panel seal (not held down by the thumbscrews.)Probably would need a good solvent clean and bakeout at minimum.The sensor though... wow! Even if it's utterly dead, this is by far the nicest thing in my spacejunk museum. The photos totally fail to do it justice.Notice the wires that are insulated with glass beads. This works best for LV signals, because there's no plastic to outgas, and the beads don't result in any trapped voids, that leak air or whatever to the chamber for a long time. A couple of wires with teflon (probably) insulation would be for signals high enough to ionize low pressure gas, so beads can't be used.Another fun thing - photo 6252. It's the transformer developing the antiphase high voltage signals to the electrodes of the quadrupole. How do you like the physical arrangement of the three windings? Not intuitive? I love it! The small thick wire air coil is the single primary. The two litz wire segmented stacks are the secondaries, in antiphase. There are internal adjustment slugs, accessible from outside the case.Edit to add: Oh, if anyone happens to have/know of the following, please PM me:- Install media with the drive software suite.- User manual for the software.- Service manual with schematics and check/cal procedures.What kind of PC HPIB card it expected (if it mattered), I don't yet know.

author: edpalmer42
author_rank: Super Contributor
timestamp: February 05, 2017, 04:32:39 am
content: I don't know if you've already found it, but this collection of brochures mentions the DQC300M RGA from ASI/Larimax.http://orionte.ipfn.ist.utl.pt/files/HugoAlves/Catalog.pdf

author: TerraHertz
author_rank: Super Contributor
timestamp: February 05, 2017, 05:12:20 am
content: Quote from: edpalmer42 on February 05, 2017, 04:32:39 amThanks. Looks like a slightly later version of one I found on the hard disk of the system. Nice for historical tracking.The manual and windows HLP file are also there, along with the application software.It doesn't look like I'm going to hear anything more from the person who replied that one time. Who hasn't responded to later questions about whether there's any reason I shouldn't post whatever I find. But give it some more time.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: February 05, 2017, 12:22:01 pm
content: Thank you for the photos of the HP quad - very nice! The coils arrangement in the RF transformer is familiar to me. The quad itself is a thing of beauty - gold plated monolithic hyperbolic.CheersAlex

author: TerraHertz
author_rank: Super Contributor
timestamp: February 05, 2017, 01:28:08 pm
content: Quote from: Alex Nikitin on February 05, 2017, 12:22:01 pmIf you'd like more detailed closeup photos of anything, just ask.I still haven't hunted for a detailed theory of how quadrupole detectors actually work. Think I understand it, but my guesses have been wrong often enough.Need to get some decent disposable vacuum-cleanliness adequate gloves, (and rtfm) before I try undoing the obviously removable parts to have a look.What do you use? Nitrile rubber surgical, with no talc? I assume latex surgical gloves would be complete fail.I noticed the inside of the vacuum chamber has a light misting of the diffusion pump oil. None I can see on the quadrupole, but of course it must be there too. Presumably that isn't good.

author: TimFox
author_rank: Super Contributor
timestamp: February 06, 2017, 04:14:06 pm
content: I don't have a reference to cite, but I remember investigating the quadrupole mass spectrometer 40 years ago and the theory behind it is very elegant, involving Mathieu functions as a solution to differential equations (originally for waves on the surface of a circular lake).For the analyzer, seehttps://en.wikipedia.org/wiki/Quadrupole_mass_analyzer, and for the Mathieu functions seehttps://en.wikipedia.org/wiki/Mathieu_function.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 06, 2017, 04:51:16 pm
content: The glass bead insulation is neat, but given that I think I see 10 insulated wires and only 4 with the glass beads they must have been desperately close on their outgassing requirements to make it worthwhile for less than 30% reduction in that element of the residual gas sources.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: February 06, 2017, 07:25:14 pm
content: Quote from: TerraHertz on February 05, 2017, 01:28:08 pmSome info here around p. 96:https://www.leyboldproducts.com/media/pdf/01/ab/0a/FVT_Fundamentals_of_Vacuum_Technology_EN57d6d275b6c8b.pdfYours Messtechniker

author: TerraHertz
author_rank: Super Contributor
timestamp: February 07, 2017, 01:52:23 pm
content: Quote from: Messtechniker on February 06, 2017, 07:25:14 pmHave been onto that since.QuoteThat's a really useful book, thanks! Saved. So good I looked for a 2nd-hand physical copy - alas none found yet.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: February 08, 2017, 02:50:43 pm
content: I usethis bookas the reference on Quadrupoles. If you want a very short version, a quadrupole mass filter combines RF AC and opposite polarity DC on the pairs of rods and works as a very narrow BPF. For a correct ratio of the RF AC and DC voltages only ions with a certain mass will make it through to the other end where the ion detector is placed, the lighter ions will be thrown out to a side in one direction, the heavier ions - also to a side but in another direction. The ratio between RF AC and DC is critical, as it defines the selectivity and thus the mass spectrum resolution. The required stability for the voltages is high and not that easy to achieve, especially for the RF AC part.CheersAlex

author: Cubdriver
author_rank: Unknown
timestamp: February 08, 2017, 11:30:27 pm
content: Back in my days at National Semiconductor, we used powder free latex gloves for everything, including work inside the hivac systems. Later, at SVG Lithography (formerly one of the Perkin Elmer divisions in CT), blue nitrile gloves were the norm. I much preferred the nitrile to the latex, as they stretched and fit tightly, rather than being loose as the latex ones at National were.For what it's worth.-Pat

author: TerraHertz
author_rank: Super Contributor
timestamp: March 05, 2017, 01:46:45 pm
content: Just a mention, I've posted a writeup of progress so far. Still a long way to go with this one.http://everist.org/NobLog/20170224_summer_vacuum_odyssey.htm157KB of text, 40MB of images linked (275 of them). Only 6MB of image thumbnails in the initial page load.Longest NoBlog article ever, by a long shot.The turbo pump and vacuum gauge on the mass spectrometer WORK!Cubdriver, to my surprise it turns out that our major hardware chain, called Bunnings, has nitrile gloves. In packs of 100, for $10. Bought a pack recently. Will post how they seem, once I've used them.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 05, 2017, 02:35:18 pm
content: Quote from: TerraHertz on February 01, 2017, 02:31:16 pmRemember some DMMs ( e.g. Fluke 87) have conductance ranges that will measure very high resistances.

author: TiN
author_rank: Super Contributor
timestamp: March 05, 2017, 03:59:11 pm
content: TerraHertzVacuum stuff is unknown to me, but I had great pleasure reading thru your article. Keep it going, I've learned few things there already

author: TerraHertz
author_rank: Super Contributor
timestamp: March 21, 2017, 01:45:58 pm
content: Progressing, mostly working on refurbishing the Helium Leak detector atm.In going through the pile of vaccum related stuff I have, I came across these two Alcatel "PL1" vacuum sensors. Unfortunately Alcatel no longer exists as such, and I can't find any data on them at all.Does anyone recognize these and have some technical data on them?They seem quite interesting, in that the only wiring is a single mini 50-ohm coax. The black connector body contains only one component wired on the socket - what looks like a small MOV.I *might* even have the driver circuits for these, since I have many of the cards from the machine these came from. But 100% certainty I will never find a schematic, and not much chance of figuring out which card/pins the coax from these attached to. Via the wiring looms, etc that I don't have.Unless someone has service manuals for an ARL FISONS 8480+ XRF X-ray Flourescence crystalography machine.Incidentally, a slightly vacuum-system related update here:http://everist.org/NobLog/20170321_machining_pool_noodle.htm

author: Cubdriver
author_rank: Unknown
timestamp: March 21, 2017, 02:28:55 pm
content: They look to me to be Pirani gauge tubes, but a quick search online doesn't reveal anything further (as you've already found).-Pat

author: TerraHertz
author_rank: Super Contributor
timestamp: March 22, 2017, 03:00:31 am
content: Quote from: Cubdriver on March 21, 2017, 02:28:55 pmNo I don't think they are. For one thing, can't do Pirani with 2-wire (unless there's a lot of intelligence inside the gauge and it's some kind of data plus power on the coax.)Reading what I can find of Alcatel stuff, they came up with some kind of monolitic mechanical vibrating thing, that works over a very wide pressure range. But not much info on it.Because these *might* be quite special, is why I'm trying to find out more. They were used in an extremely expensive machine.The hole end is slightly too small to fit my endoscope camera, darnit. There's nothing in the tube, and some 'thing' right down in the body part. But I can't make it out enough to have any idea.

author: Cubdriver
author_rank: Unknown
timestamp: March 22, 2017, 03:41:38 am
content: Hmm... I'd never heard of that. (Though I mainly worked with Balzers/Pfeiffer, Varian and Leybold stuff)I wonder if it's some sort of crystal based thing (like a film thickness monitor), but somehow set up to have the pressure change the crystal's oscillation frequency. Maybe if the crystal were either part of the wall between atmosphere and vacuum, or on a diaphragm that also acts as the wall? High pressure on both sides would let it oscillate freely, and as the pressure on the vacuum side went down the loading caused by the pressure differential would slow it down? I can't imagine that would be very accurate at lower pressures, though... (Bear in mind that this is pure speculation on my part, and I'm pulling it out of my backside!)And ofCOURSEthe hole is too small for your camera. You didn't seriously expect Mr. Murphy to exempt you from his law on this, did you?Good luck finding more info on it, and I'm curious what it turns out to be...-Pat

author: Alex Nikitin
author_rank: Super Contributor
timestamp: March 22, 2017, 11:45:27 am
content: It looks like a Pirani. Here is what I've found:http://copaseticflow.blogspot.com/2014/07/leak-detector-down-but-not-out-code.htmlhttp://www.idealvac.com/files/brochures/Alcatel_TA111.pdfCheersAlex

author: TerraHertz
author_rank: Super Contributor
timestamp: March 22, 2017, 12:56:22 pm
content: Quote from: Alex Nikitin on March 22, 2017, 11:45:27 amThanks! That is the one. Just a different mounting - theirs is a KF. And the pic of the inside of theirs shows the little light bulb mounted on the same two pins as the wiring of mine. Pretty funny to use a nice case, with 9 vacuum sealed pins, then only use two.There's an NTC thermistor mounted in series with the Pirani filament, in the connector case. It's using a spare pin as a mounting post.At around 25 deg C, my two ones measure:Filaments: 66.3, 63.8 ohms.NTC: 7.7, 7.7Oh well, they are quite ordinary. But now I really want to get a close look at the bulbs in mine. Bet they are just some standard mini-bulb, with a hole in the glass.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 28, 2017, 12:21:05 pm
content: About those nitrile rubber gloves, that I'd found at Bunnings. I've been using them and find them excellent. They're very thin, stretchy, but amazingly tough. I've been wearing them while doing metalwork for whole days, and so far no rips. Despite being 'disposable' I've been reusing the same pair for working with greasy, dirty stuff. Because they are close fitting and so thin, there's almost no loss of touch sensitivity or dexterity. Wish I'd had these years ago.Made by Ansel, about $10 for 100. It took a while to find them, since the word 'nitrile' only occurs once on the box, in the fine print on the bottom. Maybe Ansel's marketing department thinks the word sounds scary for consumers, or something. Idiots.One note: They are not impervious to MEK.