Teardown, Repair & Upgrade of an Agilent 3458A 8.5 Digit Digital Multimeter - Page 1
Forum section: electronics / repair

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 23, 2018, 02:50:34 pm
content: You can watch the video here: [48 Minutes]youtu.be/1yWjT6b1wWIThe Signal Pathwww.TheSignalPath.comwww.YouTube.com/TheSignalPathwww.Patreon.com/TheSignalPath

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 23, 2018, 02:58:14 pm
content: Hi Shahriar,Very nice fault finding and repair.Welcome in the 3458A club... and maybe you're turning into a volt-nut also.How did these initial calibration errors vanish?Have you successfully copied the content of the CAL RAM, or did you do any kind of provisional calibration?7ppm difference to your 7510A is very good, already.There's sort of a calibration sticker on the 3458A, with Jan 2018, or so, maybe calibration was still valid, or 1 year old, only.So the 3458A might be less uncertain, than your 7510A, meanwhile.Frank

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 23, 2018, 03:05:39 pm
content: Quote from: Dr. Frank on April 23, 2018, 02:58:14 pmMy next repair is about a GPS assisted OCXO 10MHz reference and its comparison with a Rubidium source. My 'nut' related problems are growing! Wait, that doesn't sound right...Somebody save me...

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 23, 2018, 03:22:00 pm
content: Quote from: Hugoneus on April 23, 2018, 03:05:39 pmWell, too late, obviously..I'm curious, how you will do the comparison, and which uncertainty of the Rb standard you'll achieve.By chance, I'm just preparing some photos of my old lab @ university (1989 vintage 3458A) , and my actual basement lab.There'll also be a picture, which shows a Rb / GPSDO comparison, but how NOT to do the calibration, in fact..Frank

author: TiN
author_rank: Super Contributor
timestamp: April 23, 2018, 03:56:39 pm
content: I wish video be longer. Also one thing to consider (but too late, because you already got meter calibrated) is to reduce oven temperature of the LTZ reference, to get better annual drift for the meter. But likely you don't care that much if it's 2ppm/year or 8ppm/year, unless you run meter 24/7 doing measurements, like some of us here.Quote from: Dr. Frank on April 23, 2018, 02:58:14 pmHe mentioned that Alltest did sponsor partially for pro calibration, so I'd assume meter was sent to cal lab at some point after the fix.Quote from: The Signal Path videoI wonder where Shahriar got that idea to pimp HP 3245A from, he-he. This source is quite interesting, only drawback of it is lack of resolution (not accuracy).

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 23, 2018, 04:28:26 pm
content: Quote from: TiN on April 23, 2018, 03:56:39 pmYup! And a few other additions if time allows.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 23, 2018, 05:14:27 pm
content: With such an old reference / meter, I would not change the temperature.The lack of dirt inside can be in part due to the air filter many other instrument are not using. There is also a chance the meter was used in a clean environment.With a meter that was not on for a long time, one should check the input filter first, before powering up: There is a chance it might blow the first time you power it up.

author: TiN
author_rank: Super Contributor
timestamp: April 23, 2018, 06:17:44 pm
content: It may also blow up later during operation as well, so that would be urgent candidate for replacement too. Thanks for reminder.

author: Kosmic
author_rank: Super Contributor
timestamp: April 23, 2018, 07:32:27 pm
content: So in the video Shahriar is saying that precision electronic should not be touched with bare hands.What is the rules of thumbs about that? What can you and can't touch with your bare hands? I guess every circuit that is high impedance should be kept relatively clean.

author: TheSteve
author_rank: Unknown
timestamp: April 23, 2018, 08:02:56 pm
content: Shahriar, is there a reason you chose to use battery backed memory for the memory upgrade?

author: guido
author_rank: Regular Contributor
timestamp: April 23, 2018, 08:40:31 pm
content: Great video as always.I was only wondering about the IC sockets you are using. Not the round ´turned pin' type, but regular cheaper sockets. I would not use those in such an instrument. Actually i would only use those for 'disposable' test PCBs.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 23, 2018, 09:48:51 pm
content: to touch bare hand sensible electronics is a no no, the skin oil etc .. may create problems, i use nitrile gloves ... when at my job i touch a ultra clean gold plated pcb with no added parts on it, it leaves residues i have to clean the pcb with special cleaner to be sure there is no contaminant, because it may interfere with the solder paste we apply with silkscreen.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 24, 2018, 04:21:23 am
content: Quote from: TiN on April 23, 2018, 03:56:39 pmIsn't alltest that company in New Jersey with the shady practices? I don't think I would buy any "for parts" unit from them. Their deal with Shahriar looks like a clever marketing ploy to get a new round of gullible buyers. They could have gifted him with a special unit which would make it appear fixing them is much easier that it usually turns out to be.

author: BravoV
author_rank: Super Contributor
timestamp: April 24, 2018, 04:29:15 am
content: Quote from: Kosmic on April 23, 2018, 07:32:27 pmWhat about the burst of mist of saliva as he speaks probably in front of the board during the video shoot ?To proof it, just stand quite near a window glass and speak normally, you will easily see specks or tiny spots spread at the clear glass.

author: Samogon
author_rank: Frequent Contributor
timestamp: April 24, 2018, 05:31:03 am
content: Quote from: chickenHeadKnob on April 24, 2018, 04:21:23 amYes they are.But for easy repair i would not be so confident, it is always looks pretty simple to follow experienced guide. And when it gets in your hands, you can easily spend tens of hours in wain.

author: Kosmic
author_rank: Super Contributor
timestamp: April 24, 2018, 02:43:52 pm
content: Quote from: Samogon on April 24, 2018, 05:31:03 amI bought a power meter "as-is" from them some time ago and it wasn't that bad. Shipping was a bit high but the description of the item was accurateFrom what I saw from their ebay listing they tend to add a lot of details (they do more than power-up test). But shipping is always expensive (to Canada at least).but yeah, there's always an inherent risk when buying broken/as-is equipment.

author: lukier
author_rank: Unknown
timestamp: April 24, 2018, 03:40:56 pm
content: Quote from: chickenHeadKnob on April 24, 2018, 04:21:23 amYup, it seems an old 3458A is very cheap way for them to improve their public image.I never really bought anything from them because most stuff they list are not a bargain by a long shot and they have completely random shipping costs.I was seriously considering buying some LeCroy WaveLink active probe tips, 3 pcs for $300 or something similar, but the shipping to the UK was $450.26 (these things are very lightweight, probably 200g for the lot).When I asked about why the shipping cost is so outrageous they've said they can ship with USPS and asked me to buy it now and they will revise the shipping costs later (and they didn't say to what amount). It all sounded very dodgy so I gave up. Why not list the shipping cost to the UK properly in the first place or do things via eBay and not some later revise gentleman's agreements, or even better, use eBay's Global Shipping scheme. Very strange company indeed.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 24, 2018, 03:50:47 pm
content: Hello ShahriarYou found that fault very fast, respect !Very nice video again, thanks for sharing!

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 24, 2018, 09:05:14 pm
content: If you have issues with AllTest’s shipping you should let them know. As far as I can see, that seems to be the biggest complaint.Also note that I asked for a broken instrument. They could also send me a working one. But I think a repair is a more interesting video.

author: lukier
author_rank: Unknown
timestamp: April 24, 2018, 09:28:14 pm
content: Quote from: Hugoneus on April 24, 2018, 09:05:14 pmTheir eBay listing policy is quite odd, some people here on the forum had much bigger problems than just exorbitant/random shipping costs. As I've said, even without the shipping quirks, their prices are often not very attractive for a hobbyist anyway.As importing from the US can be expensive and/or problematic I have much lower bid threshold for uncertain sellers/listings, especially if the price is not a real bargain and the seller doesn't offer Global Shipping Programme.Quote from: Hugoneus on April 24, 2018, 09:05:14 pmSure, the video is great (I don't click on thumbs-up very often), nice repair and you got lucky it is not the infamous drifty ADC problem which is pretty much game over. Hope to see some interesting experiments with this meter

author: dr.diesel
author_rank: Super Contributor
timestamp: April 24, 2018, 10:10:39 pm
content: Quote from: chickenHeadKnob on April 24, 2018, 04:21:23 amYup,https://www.eevblog.com/forum/metrology/datron-4910-on*bay/msg1128954/#msg1128954

author: mbless
author_rank: Regular Contributor
timestamp: April 25, 2018, 02:17:23 pm
content: Quote from: dr.diesel on April 24, 2018, 10:10:39 pmOh wow, so Alltest is express_test on ebay?Concerning TSP, does anybody know what the little 5V reference is that Shahriar uses?

author: dr.diesel
author_rank: Super Contributor
timestamp: April 25, 2018, 02:27:13 pm
content: Quote from: mbless on April 25, 2018, 02:17:23 pmOne of these variants:http://www.voltagestandard.com/DMMCheck_Plus.html

author: plesa
author_rank: Frequent Contributor
timestamp: April 25, 2018, 06:51:35 pm
content: Wauu respect for such fast repair. My convergence error ended up with A3 board replacement.

author: BU508A
author_rank: Super Contributor
timestamp: April 27, 2018, 08:07:21 am
content: Shahriar,thank you very much for this interesting video.Quote from: Hugoneus on April 23, 2018, 02:50:34 pmI would have been really appreciated, if the video had another 12 minutes or more, so it could be sponsored by Patreon. It'll be really worth it imo.Looking forward to your next video.Thanks,Andreas

author: hendorog
author_rank: Super Contributor
timestamp: April 28, 2018, 09:51:50 am
content: Quote from: mbless on April 25, 2018, 02:17:23 pmI don't have an issue with their 'test it fully when someone buys it, fix if required' approach. I think that is probably a standard modus operandi for a huge surplus dealer - and is exactly what happened to a friend when they ordered something from a different large US based supplier of used test gear.However I do think their list pricing is way out of whack. 5% Signal Path discount needs to be more like 55% to get even close to the market. I'd also be very nervous buying anything marked 'parts or repair' from a company who clearly have significant repair capability. How do I know I'm not getting a stripped down parts mule which has been raked over for anything of value?

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 28, 2018, 12:08:00 pm
content: Quote from: hendorog on April 28, 2018, 09:51:50 amWell this was exactly my point. They are a repair depot with a large stock of test equipment and 4 repair techs. The only way the business model sustains itself is if they have a large volume/throughput of working units which fetch premium dollars and some cannibalized hulks which they unload on suckers. I thought they screwed over TiN in misrepresenting the contents of the for parts 3458a they sold him. You would stand a better chance buying from joe random seller. It should be recognized that it was marketing genius engaging The Signal Path though.

author: Samogon
author_rank: Frequent Contributor
timestamp: April 28, 2018, 01:15:04 pm
content: Cannibalized or failed repair attempts, which can be even worse.

author: TiN
author_rank: Super Contributor
timestamp: April 28, 2018, 04:06:15 pm
content: QuoteThey "lost" 3458A I've bought originally, and shippedanother 3458Ainstead with a 30% discount, so it the end I wasn't too sour about it. Yes, we ended up buying missing A5 and replacing A3 ADC board and bunch of other parts, but hey, I did not expect fully working meter for 500$ either. If they sell another dead 3458A for 500$, I'll probably take it again.If Hugoneus got 3458A presented in video indeed donated to his lab, well, I see nothing wrong with that, quite the opposite.Too much advertisement? Well, didn't we all learned to ignore it by now, and use own gray wetware to decide on deals?

author: hendorog
author_rank: Super Contributor
timestamp: April 29, 2018, 12:04:09 am
content: Quote from: chickenHeadKnob on April 28, 2018, 12:08:00 pmAh OK - I couldn't tellThe issue about advertising as working, but not actually testing until after purchase was something people complained about in one of the old threads about express_test.

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 29, 2018, 04:08:08 am
content: Quote from: hendorog on April 29, 2018, 12:04:09 am-False advertisement in auctions-Lying about repair timeline-Feeding same bullshit repair timeline to more than one person after auction was relisted / re-sold after first purchaser waited over a month for repairs.-Accuses to sue for bringing their practices to lightMy place of work has also made a multiple(5-6) item purchase from ExpressTest/Alltest before. 1 would power up but not function, the other wouldn't pass calibration and needed to be returned.This is, clearly, a clever marketing ploy to gain a resurgence in their plummeting sales.

author: lukier
author_rank: Unknown
timestamp: April 29, 2018, 06:28:03 am
content: Quote from: TiN on April 28, 2018, 04:06:15 pmThat is not how this works. If I will be looking for precision test gear I would value your opinion higher than some random comment from 9gag. The same with TheSignalPath, being an RF noob, I would take his advice seriously any time.Look at the YT comments under this video:"...I love their bargain prices..." (strange to hear about a company that sells an old used 3458A for 66% of the brand new price),"Will keep AllTest in mind for next purchases.﻿""Good on AllTest to 'sponsor' this!""Glad to know about AllTest""I'll definitely consider Alltest for my next instrument purchase.﻿"So either some troll army or the endorsement works.I realise that these video blogger - company relationships are difficult and it is a fine line.My gut feeling tells me that big brands are probably safer, as while there are no saints (Adafruit - Fluke case ,FTDIgate, Siglent trademark troubles), their primary focus is to develop new products that can be reviewed on their own merit and in the end it somehow benefits the community, even if only 20 years later when the second hand prices become affordable for a hobbyist.At the same time most equipment traders work against the community, using their power to take truckloads of surplus/auction equipment off the market and as people have mentioned sell some way above the market prices and the rest as cannibalised units for parts.

author: MadTux
author_rank: Frequent Contributor
timestamp: April 29, 2018, 09:47:39 am
content: I'm not completely sure, but it seems that some of the ExpressTest/Alltest critical comments have disappeared from youtube. Not a nice practice, but common at youtubeI probably won't ever buy from them again due to shady practice of "disappearing" items and crazy shipping costs. I scored some nice TLA700 plugins for cheap a while ago and after they found out that they made a mistake, the the plugins simply disappeared from inventory. They canceled the sale and claimed the tech can't find it in the warehouse instead of being honest and confessing a listing error. A while later, the same plugins got relisted for like 10x the priceAlso bought 2x Keithley 617s from them for parts/repair a long time ago (paid 300$ total or so). The arrived more like part kits that required lots of repair because an incompetent tech butchered them and was changing parts at random. Got them working eventually, so it's fine for me. But in retrospect, I wouldn't have paid 300$ for that mess.Current shops on ebay:https://www.ebay.com/usr/express_testhttps://www.ebay.com/usr/express_auctions

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2018, 11:02:19 am
content: Quote from: MadTux on April 29, 2018, 09:47:39 amYou mean at this particular Shariar's video ? As I didn't read the comments.

author: MadTux
author_rank: Frequent Contributor
timestamp: April 29, 2018, 11:29:59 am
content: Yes, I think there were a few critical 1-liners such as: "Beware of alltest-equipment" or "Their shipping costs are insane" etc. that disappeared.Can't prove it, since I don't have screen shots, but that sort of thing is happening quite often on youtube on these sort of videos.

author: cheeseit
author_rank: Regular Contributor
timestamp: April 29, 2018, 12:14:03 pm
content: If so, I assume this would be the channel owner deleting? I use Youtube a lot but I'm not that into the mechanics so can enough down votes cause a comment to be hidden?This appears to underscore how fine a line a content creator has to walk regarding sponsored content not to get into some kind of trouble with the core audience. I find that comments on Youtube mostly are a waste of time, except for some types of content, so I rarely read them. Too many idiots and 'FIRST's usually.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2018, 12:29:50 pm
content: Quote from: MadTux on April 29, 2018, 11:29:59 amI guess its up to Shariar to clarify this.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 29, 2018, 02:39:18 pm
content: Quote from: BravoV on April 29, 2018, 12:29:50 pmI have not erased any comments from YouTube. There are a few reasons for this:1) I do not have the time to moderate comments.2) I have no vested interest in AllTest or any other vendor. I get nothing from their sales or success and certainly a comment saying “their shipping cost is high” etc. is not even a bad thing. People should know, that is how vendors improve themselves. I said in this thread as well that people should let AllTest know if there is something they don’t like about them.3) Sometimes YouTube moves a comment to “Likley Spam”. Every once in a while I go through the list and try to approve comments which are there incorrectly. But as I said, I don’t have the time to do this regularly.4) The only few occasions I have ever erased any comments on my videos has been when trolls have attacked other users or downright insulted someone for no reason.5) If I was concerned about people posting negative comments about a vendor, I would not cross-post my videos on platforms which I have no control over.I (hope) people prefer that I spend my time making more videos than moderating the comment sections.

author: rfengg
author_rank: Regular Contributor
timestamp: April 29, 2018, 11:20:01 pm
content: Guys, give this man a break......He puts out some of the best RF videos on youtube with concise , precise explanations of his thought process that all of us can learn a lot from.Surely he deserves more than this.....Hope the negative comments do not put him off from continuing the great work that he has been doing.I'm sure the majority of us have benefitted from his videos, so hope the trollsback off.

author: Samogon
author_rank: Frequent Contributor
timestamp: April 30, 2018, 03:45:23 am
content: May be i miss something, but none of bad words was written towards Shahrir.Shame that this interesting topic drifted away from technical to ethical.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: April 30, 2018, 06:30:17 pm
content: Quote from: Samogon on April 30, 2018, 03:45:23 amI didn't feel attacked in any way in this thread.But I do wonder about the whole psychology of YouTube. Take my channel for example. I try to make videos targeting more advanced topics, often up to an hour long. They are available to everyone for free. A 1 hour video can take a whole day (or more) to make. Especially the reviews, because I need to design all the experiments, test them and prepare the whole video to flow in such a way that the audience would find it useful regardless of whether they intend to buy the product or not.The advanced topics combined with the length of videos means that my channel's growth will always be limited, but I genuinely believe that those who find the videos useful, find it very useful. And that makes it worthwhile. The occasional hate, unwarranted conspiracy theory generators and the thumb-downs within the first 5 minute of the video release don't deter me. If they did, I would be doing consulting in the industry in my free time.

author: Kosmic
author_rank: Super Contributor
timestamp: April 30, 2018, 08:06:04 pm
content: Telecommunication is pretty much like a amplifier. You can't just amplify the signal of interest. Unfortunately noise get amplified at the same time. As long as the signal to noise ratio is good we are okI'm seeing a lot of good things on internet, so or ratio is still probably okShahriar, you videos are more than welcome! please ignore the noise and keep it coming

author: GerryBags
author_rank: Frequent Contributor
timestamp: April 30, 2018, 08:47:26 pm
content: Quote from: Hugoneus on April 30, 2018, 06:30:17 pmWell, ofcourseThe Signal Path has an excellent bullshit filter!