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| Keithley DMM6500 transformer: RFC around recall experience, and a dilemma |
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| Hydron:
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. |
| arcitech:
--- Quote from: Hydron on July 11, 2022, 10:52:54 pm ---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. --- End quote --- Thanks for the sanity check. I had hopes of a forehead-smacking eureka moment, but no such "luck"... |
| thm_w:
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 thread --- Quote ---Thanks for the feedback. We are aware that some users consider the transformer and fans loud. BUT If you have big vibrations, you should consider that you have a faulty unit and send it in for service. I am fairly certain no units ship with big vibrations or excessive audible noise (it is checked). Some people are more sensitive to it than others. :-// --- End quote --- --- Quote ---The transformer design and housing is the way it is completely for cost and mechanical reasons. However, this has actually made the hum problem worse. It turns out that this metal bracket actually vibrates and sort of resonates the sound not only from the natural transformer vibration but introduces larger harmonics of it. The transformers are *double* dipped in varnish AND the metal bracket has an epoxy fillet along the perimeter of the mounting to help dampen vibrations. Yet still, some hum can be heard in some cases. The factory has some controls in place to make sure it is not "too bad" -- again though, this is subjective! --- End quote --- Your 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 |
| arcitech:
--- Quote from: thm_w on July 13, 2022, 10:18:14 pm ---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. --- End quote --- The 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 pm ---If yours was really bad, then you would have noticed when it was purchased. --- End quote --- I 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 pm ---Your 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 --- End quote --- A 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. |
| LinuxHata:
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. |
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