Keithley DMM6500 transformer: RFC around recall experience, and a dilemma - Page 1
Forum section: electronics / testgear

author: arcitech
author_rank: Regular Contributor
timestamp: July 11, 2022, 05:37:42 pm
content: The short & objective bit:Who among the DMM6500 owners out there has experience around the "warranty service recall" issued to replace the early batch of transformers they can share?If you've had your transformer replaced, could you share your unit's original shipping date? Do you happen to know what the label on the problematic transformer was, or what the new one is after replacement? And could you comment on the process overall? Lastly, unless it's covered by NDA, could you share the verbiage of the original advisory sent out to owners who'd been identified as affected? (I'm specifically interested in whether there is any safety / fire hazard facet at play here, and less importantly, performance degradation.)The longer and subjective bit w/ a dash of rant:The unit I'm responsible for is a couple months out of warranty (late Apr 2019 orig ship date), and the standby noise it emits (while "off" but not unplugged from mains) is unfortunately amplified by the furniture the unit sits in (despite some NVH help from the bumpers).Keithley support will not confirm whether my unit falls within the scope of the "warranty service recall" despite having provided a photo of the label on the transformer assembly ("B-2570/71-ASSY 120221704 Rev.A") spied through an opening in the chassis (w/ cover slid back), and with a decent-enough audio clip of the buzz in standby, through a boot cycle, then back off in standby.Instead I'll need to make a pricey wager to have it sent in for evaluation and:QuoteThey're tight-lipped on how some sort of warranty could apply to a unit with an expired original warranty and no other extended options (and I'm told the reasonably-priced "AREPAIR" extension for one year after orig warranty would not cover this issue).So, my possible outcomes from best to worst are:0) Evaluation determines replacement falling under "any type of warranty" applies. Issue gets fixed.Total cost: $01) Evaluation determines replacement would not fall under "any type of warranty". Service is declined, and my company's card on file is hit for the cost of evaluation + shipping. Nothing gets fixed.Total cost: >$8002) Same as #1 above, but service is approved. "he full cost of repair could be $2400 and the evaluation fee would be waived." Things get fixed.Total cost: ("could be") $2400Dave thinks "they're takin' the piss" on that last outcome:https://youtu.be/0Xme4FcaUkI?t=4601Without any first-hand insights from the community and leaning only on info I've gleaned from 'round the web, I'm on the fence between taking the gamble, or spending $400 more than the cost of outcome #21 to simply purchase a new one from Tequipment and sell this one to someone whose lab isn't as quiet as the one this unit lives in (or whose stereocilia wouldn't pick up on it to begin with).(And no, my frustration around this isn't why their domain's got some serious DNS issues, though it did prompt me to check upon realizing their site was down over the weekend whether I could leverage a lapsed registration!)

author: bdunham7
author_rank: Super Contributor
timestamp: July 11, 2022, 05:48:59 pm
content: Are you and the service center in the US? If not, where are each of you?Occasionally you see this type of 'fuck-you pricing' but I'd be pretty shocked if that was all direct from Tek/Keithley in the US. If that's how it actually is, then buy-sell seems to be the best plan to me. And look at other vendors in the future perhaps? Although we seem to be running out of them...

author: arcitech
author_rank: Regular Contributor
timestamp: July 11, 2022, 05:55:27 pm
content: Quote from: bdunham7 on July 11, 2022, 05:48:59 pmYes, the unit and I are within the continental US; I'd guess the same holds true for the CSR who's written the emails. It took a number of days from Tues AM until nearly EOD Friday just to begin to engage w/ someone on the "right" team.

author: arcitech
author_rank: Regular Contributor
timestamp: July 11, 2022, 06:01:09 pm
content: Quote from: bdunham7 on July 11, 2022, 05:48:59 pmI debated about sharing this sanitized message initially. "Legal said it was okay" and that it doesn't even have one of those meaningless scare tactic signatures....Maybe the author "A" was the hacker that brought them down, and decided to take the piss at my expense before turning off their domain(s)...

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 11, 2022, 06:03:03 pm
content: I sent my DMM6500 for warranty service for the noise issue (first month of warranty or so). Came back fixed but "no changes done" according to the manual...Bought it Oct 2020, RMA'd Dec 2020 via the web form, received it back Jan 2021.

author: bdunham7
author_rank: Super Contributor
timestamp: July 11, 2022, 06:07:02 pm
content: Well if all that accurately reflects their intended policy, then clearly they are telling you in general to buy their maintenance plan or fuck off. And in this specific instance, the latter. The $800 to tell you that it isn't in warranty and to not fix it seems to be the most outrageous part. I've actually observed a fair number of companies that have responded to the last few years of chaos and the current rising cost/high demand/low unemployment environment by implementing policy changes that appear to have the sole purpose of destroying customer goodwill and reducing customer loyalty. And it is hard to explain some of these changes with incompetence, so perhaps actual malice is involved.

author: mawyatt
author_rank: Super Contributor
timestamp: July 11, 2022, 07:30:58 pm
content: Didn't think a DMM6500 cost so much, basic unit goes for ~$1400 here is US. Our DMM6500 was a purchased in late 2021 and doesn't have any apparent noise issues, very quiet.Anyway, agree with OP leaning towards getting a new unit and selling noisy one, as near $2400 seems like a very expensive noise reduction cost.Good luck and hope you get this resolved.Best,

author: jonpaul
author_rank: Super Contributor
timestamp: July 11, 2022, 08:37:38 pm
content: noisy mains transformers are poor quality, often off-shore junk.The OEM cost of an instrument 20..100w multiple output transformer can be $7...25.Loose laminations, poor varnish, etcJon

author: arcitech
author_rank: Regular Contributor
timestamp: July 11, 2022, 08:53:49 pm
content: Quote from: bdunham7 on July 11, 2022, 06:07:02 pmThat they're unwilling to positively identify my transformer as within (or beyond) the bounds of the recall is what startles me the most. From the start, they knew the DMM's SN; later after I learned of the $800+ wager I provided a photo peering through the chassis opening that puts the label in plain view. Still the CSR was unwilling to comment on whether this is or is not within the bounds of the recall. I mean, it's not as if they'll open the unit up to find a couple Bud Light empties and some cigarette butts, and even if they did, what's at risk by confirming whether my unit's among the known bad ones?Quote from: jonpaul on July 11, 2022, 08:37:38 pmThis is a "Signal Tranformer" assembly made in DR. This is a subsidiary ofBel Fuse. I've not heard back from Signal Transformer's support email regarding date code confirmation of my unit or any applicable recalls they're aware of. All the replacement assemblies I've seen shared online have a label containing a styled logo, compared to labels such as that on mine which is some simple sans (Ariel?) text.Maybe they just took offense to what I titled therecording.

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 11, 2022, 09:30:38 pm
content: Quote from: jonpaul on July 11, 2022, 08:37:38 pmI've read in one of the DMM6500 threads that it's due to improper mains voltage selection. The transformer in the DMM6500 is IIRC a relatively expensive special construction using coaxial cable, so it would be weird if they cheaped out on stuff.

author: Hydron
author_rank: Super Contributor
timestamp: July 11, 2022, 10:52:54 pm
content: I'll have a look to see if I have any before pictures of the transformer before I got mine fixed. Had no issues getting it RMA'd, though it was in warranty, and arrived back with a new quiet transformer and a fresh calibration.The numbers you've been quoted are crazy - even $800 for a complete fix would make me wonder if they're looking at the wrong price list, let alone 2400 which would buy 2 new units! Given it's a known problem the warranty status really should be irrelevant anyway, they should just fix it. Only redeeming feature of paying out would be the fresh calibration.One quick check that I'd suggest before going too much further is to check that it's not set to 100V instead of 120. The hum definitely reduces with lower line voltage, suggesting that the root cause is that it's a little closer to saturation than is ideal (sadly this seems to be a pretty common characteristic in small transformers these days). Note that in my case I had it correctly at 240V (though my mains is more like 250, which didn't help matters).Funky coax transformer is the DMM7510, the 6500 uses a double transformer thing for commonality with the DAQ version but it's a standard iron core job otherwise.

author: arcitech
author_rank: Regular Contributor
timestamp: July 11, 2022, 11:07:11 pm
content: Quote from: Hydron on July 11, 2022, 10:52:54 pmThanks for the sanity check. I had hopes of a forehead-smacking eureka moment, but no such "luck"...

author: thm_w
author_rank: Super Contributor
timestamp: July 13, 2022, 10:18:14 pm
content: I can't hear a thing in your recording, but, its not the kind of sound to easily record. Regardless, there was no real "recall" it was just Tek exchanging units under warranty that were really bad. There was never a "defect" with the transformer itself, so messaging the manufacturer is pointless.If yours was really bad, then you would have noticed when it was purchased.Quote from the DMM6500 threadQuoteQuoteYour realistic options are:- Open it up, add some dampening/glue/rubber whatever to the transformer and bracket, find different furniture to mount it on- Buy another unit as mentioned above

author: arcitech
author_rank: Regular Contributor
timestamp: July 14, 2022, 12:05:22 am
content: Quote from: thm_w on July 13, 2022, 10:18:14 pmThe Tektronix Support response I received confirmed a known issue with these words before advising I contact Service / Repair:"During the initial release of the DMM6500 in 2018, there was an issue related to the varnish applied to a transformer that caused a buzzing."This was identified after the first release, however, and all customers were urged to return the units for warranty service to resolve the issue, if affected."That sounds like a recall to me. Am I putting too much weight on the word "urged" and, instead, should read it as "invited"? My sense of urgency around this issue doesn't seem like it was injected without basis, though if it was simply just a case of taking words at face value when I shouldn't have, hopefully the above justifies my "mis"interpretation.Quote from: thm_w on July 13, 2022, 10:18:14 pmI did --I've had it for a hair over a week. In my quest to keep the saga short at the outset, it seems I failed to include that. (I thought I had, truthfully.) I've been forthright about that w/ Tektronix, for sure. It was picked up on the second-hand market (for a fair price from someone who I'll likely be able to call a new friend) because an order 2wks ago from TEquipment was estimated for shipment in November. Then, days after I unbox mine, they have 19 in stock (and 55 a couple days after that). Endless sighs & fist shakes on that front. (But the forum discount gives 'em a lotta leeway!)Quote from: thm_w on July 13, 2022, 10:18:14 pmA newer one's almost certainly in the cards, even if the megacorp dayjob decides to push back against broader adoption because outside the 3/4/5yr warranty bubble, things get very illogical. I have a feeling though that this is a case of one very incorrect CSR who decided that exactly zero of the on-demand repair options apply to my unit, which according to the model-/SN-based options cap a repair at $695 (unless the cal is accredited)... a far cry from over two grand, and seemingly devoid of any need for some >$800 evaluation fee.I do really hope this is just a case of a simple word choice that made a situation seem more urgent than it should, coupled with a seriously confused CSR whose pricing does not align whatsoever w/ the options shown online.In any case, I'll wade through sorting what the actual options are just to be sure I can be up front w/ whoever intends to purchase the thing, even if there's slim chance they'd even hear it let alone care. Thanks thm_w for dialing down my worry knob a decent bit.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: July 14, 2022, 05:33:52 am
content: Are specs of transformer known?I would order custom replacement model in China.I have ordered several 250W custom wound transformers in China.Costed me around $100.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 14, 2022, 06:01:15 am
content: If the specs are not known, it would be relatively easy to measure the required specs (voltage and VA rating - the primary voltage is obvious). The VA rating is anyway approximate and not a brick wall.A point is that the transformer should include shields (one on each side - though they may have cheaped out with a single shield) and ideally an extra degree of isolation from the primary to scondaray. So it is not a normal transformer. Nothing very high tech, but off the normal path and may need extra communication and this could make it tricky in China.For some reason they use 2 transformers - which may be due to space constraints.AFAIK quite some of the power is there for a potential extension / relay card and not just the plain DMM.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: July 14, 2022, 06:13:21 am
content: I have experience of ordering a special, medical grade transformer manufacturing in China.Nothing special, quite solvable even with google translate......

author: arcitech
author_rank: Regular Contributor
timestamp: July 14, 2022, 09:25:58 am
content: Signal Transformer communications indicate the design is behind NDA and can't share the specs. They also abstained from confirming whether any absence or presence of a safety issue is known with these early, apparently problematic, units.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: July 14, 2022, 07:05:12 pm
content: Well, unless it is heavily potted, it is quite possible to unwind each winding, measure number of turns and wire diameter, along with cross section of steel

author: mawyatt
author_rank: Super Contributor
timestamp: July 14, 2022, 07:23:53 pm
content: If nothing else works, consider removing the transformer and dipping it in potting compound a few times to hopefully subdue the vibrations. Start off with a highly thinned compound to allow it to wick into the windings, then thicker compound to cover and add mass, and so on.Good luck,Best,

author: thm_w
author_rank: Super Contributor
timestamp: July 14, 2022, 08:57:26 pm
content: Quote from: LinuxHata on July 14, 2022, 05:33:52 amAbsolutely not worth the time.Mawyatts suggestion of dipping it, if it is easily unplugged or removed, may make sense. But I would start probing around with my hand first to see if something else is shaking that could be glued/rubbered.

author: stigskov
author_rank: Newbie
timestamp: October 15, 2025, 11:33:47 pm
content: Realize this is an old thread, just wanted to add a reply in case someone searches for this issue.You may be able to repair the transformer by shorting out the thermal fuse. The Thermal fuse is wound-in close to the core, see schematic illustrationCarefully cut the tape close to the iron core and peel back.Also peel back the plastic piece right under the tapeThe White wire is soldered to one end of the thermal fuse, a thick wire going into the transformer. The other end of the thermal fuse (Also thick wire) is soldered to the first winding to the transformer - you have to gently cut another layer to get to it.Short out the thermal fuse by soldering the 2 thick wires together (see picture)Most likely only the main transformer B-2570 is failing, and the second transformer B-2571 is ok. Primary inputs are the same on both transformers but the secondary output of B2571 (2x Brown) measures ~ 8.5V unloaded.You should'nt worry about disabling the thermal fuse, the reason it's blown is most likely because it's under dimensioned and the instrument has the TSP-Link option installed and been sitting in an overheated rack together with lots of other instruments. If the transformer fails again, the fuse will simply blow. If paranoid, find 2 or 3 seperate/suitable transformers at Digikey and mock them into the boxHope it helps

author: Kleinstein
author_rank: Super Contributor
timestamp: October 16, 2025, 07:46:24 am
content: The thermal fuse is there for a reason: it's there to prevent fire in case of a failure. A normal overcurrent fuse could do much of the job, but a replacement thermal fuse, even if not so well placed would be an option.