Brand new ET5410+ emits high pitch noise - Page 1
Forum section: electronics / testgear

author: hp3310a
author_rank: Regular Contributor
timestamp: January 29, 2025, 12:42:13 pm
content: Hi everybody,I got a brand new East Tester ET5410+ electronic load today and immediately ran into a problem that I didn't *hear* about in any video review: It emits a constant, loud and mind numbing high pitch noise at around 8kHz (give or take). I'm attaching an audio recording where you can hear it in the background (you may need to crank up the volume above normal). In reality this noise is much louder and the fan noise is not as loud as it sounds in the recording.So first question: Did anyone else experience this with their new ET5410+? If so, does it go away? Is there a fix or do you have to tolerate that?I also noticed that the fan runs on slow revs when idling after boot up and never shuts down. It's in a 10°C environment so heat can't be an issue.Any pointers really appreciated!

author: hp3310a
author_rank: Regular Contributor
timestamp: January 30, 2025, 04:26:55 pm
content: I uploaded a video for more context:

author: thm_w
author_rank: Super Contributor
timestamp: January 30, 2025, 10:59:16 pm
content: I can't really hear anything, you can use a FFT app on your phone to see what the frequency is.Then maybe try adding a load and see if it shifts/increases/decreases.Its not unusual to see on electronics, and some units may have it worse than others.

author: gamerpaddy
author_rank: Regular Contributor
timestamp: January 31, 2025, 04:17:36 am
content: fft shows a peak at 6660hzolder ET used a transformer.. this one uses a switching psu. 12V 1Aone of the lowest quality ones available, not a single filter and junk caps on it

author: DaneLaw
author_rank: Frequent Contributor
timestamp: January 31, 2025, 05:38:09 am
content: Quote from: gamerpaddy on January 31, 2025, 04:17:36 amThat also, explains a good part of the weight reduction, which went from around 3.7kg on the older ET5410 down to 2.9kg on the new "enhanced" ET5410+.. also seems they made quite a few other downgrades... according to users should the metal framing around the front, be gone on the +version.I don't know if anything else has been changed.- but in East Tester corporate wording-limbo, they just enhanced it, but "enhanced" for who.. the users, or their financial bottom line, likely the ladder.I haven't noticed any high pitch on my unit, but it's the older variant, so not that comparable.A brief video from each side of the internals of my unit' if you wanna analyze parts that differ between ET5410 and ET5410+.

author: hp3310a
author_rank: Regular Contributor
timestamp: January 31, 2025, 03:38:37 pm
content: Here's the FFT, mic next to the air intake at the front of the idling unit. One peak (the one that I can hear clearly) is at 7kHz, another almost equally powerful one is at 13kHz (that one I probably can't here). On the low end of the spectrum is the fan.Not sure yet were the noise comes from, I need to wait what the vendor has to say about it before I open the unit. Could very well be the power supply at the rear end but equally well the LCD. I don't see what would make such noise on the two main boards (but what do I know).The noise stays the same under load.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 01, 2025, 03:45:48 pm
content: So, the vendor responded and suggested I repair the unit. Not sure if I'm going to do that, but I was curious whether what he said was right.First of all, this is my power supply, doesn't look as shabby as it was suggested earlier. I disconnected it and let it run without connection to the board. It's completely silent, also when it is connected.I powered the board from a lab supply to rule the noise is coming from the power supply, maybe indirectly due to ripple. Nope, still there, loud and clear.It is this chip that makes the noise, next to the power supply socket.The vendor suggested as much also said what it is: ME7660, a charge pump DC-DC voltage converter (https://www.ic72.com/pdf_file/m/421650.pdf). I put a finger on it and the sound changed. Tried the same with the capacitors nearby but that didn't change the noise.So I guess the culprit is identified, but will a replacement be any better? With my luck it will be exactly the same or worse.BTW: I keep failing to insert images the way other people do with a small expandable image inline, expanding inline to a big version when clicked. My images always open a new page when clicked instead of just changing size. What is the correct board markup to do that inline expansion thing?

author: Grandchuck
author_rank: Super Contributor
timestamp: February 01, 2025, 04:03:29 pm
content: C78 or one of the other ceramics? They can "talk" due to the piezoelectric effect.

author: beatman
author_rank: Regular Contributor
timestamp: February 02, 2025, 01:44:50 pm
content: Maybe try to resolder all the SMD componeds there and the chip to see if something change.

author: ledtester
author_rank: Super Contributor
timestamp: February 02, 2025, 02:32:18 pm
content: Quote from: hp3310a on February 01, 2025, 03:45:48 pmI think it has to do with the resolution of the images. In a lot of cases you can reduce them down significantly without sacrificing clarity.

author: thm_w
author_rank: Super Contributor
timestamp: February 04, 2025, 10:51:45 pm
content: I've never had the IC itself generate significant noise, its always the capacitor or inductor.That said there are tons of 7660 clones, likely with varying frequencies/rise times/etc. So you could swap that out, or swap the caps out as mentioned.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 05, 2025, 03:18:44 pm
content: Thanks for the comments. The seller and I came to an agreement and I will try to fix the unit by replacing the charge pump chip and its surrounding capacitors. I will probably also replace the power supply because it only produces 11.7V and while using the lab power supply at 12V to see if that makes a difference didn't change anything wrt the noise, it will probably not hurt either. Plus a 12V 1A supply isn't very expensive. I'll report back once this is done.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 17, 2025, 05:01:50 pm
content: So the replacement chips arrived and I went to work.After desoldering the old one - which was actually a TP7660 not an ME7660 (has the same function and is pin compatible) - and soldering a new ME7660 in its place I discovered...Quote from: thm_w on February 04, 2025, 10:51:45 pmthat you were right, the noise was still there and not a bit less loud. I also found that...Quote from: beatman on February 02, 2025, 01:44:50 pmthis was a good suggestion, too. The old chip had a cold solder joint (on the output pin) that was clearly visible when I lifted it.I don't have the necessary 0805 10µF capacitors here but I have some electrolytics, so I tried those.Looks terrible but it works, sort of. The noise got a lot less loud but I can still hear it. So one of the ceramic capacitors was involved (both were about the correct capacity), but there's at least one still producing unwanted sound.Since I don't know which I would have to desolder each one, measure it and order a replacement. That's rather error prone, does someone know the right values?Also which ceramlcs are less likely to produce such noise, is there a brand were this doesn't happen as a matter of principle (or quality)? The two through-hole caps will be replaced too, once I found the other culprit(s).Before all this happened I also discovered (under the microscope) that the TP7660 apparently was hand soldered and so was a second capacitor on top of the 1206 to the right of the chip. I didn't notice that in the earlier pictures I had taken. So this was not a new unit but a returned one with a failed repair attempt, great.Not sure how to determine the intended capacity of the stacked cap, the value that my LCR tweezers spit out likely are not what it is supposed to be.

author: wraper
author_rank: Unknown
timestamp: February 17, 2025, 05:08:15 pm
content: Quote from: hp3310a on February 17, 2025, 05:01:50 pmCould be a factory thing. Something being hand soldered (unless you bought used) usually does not mean it's a returned unit. Use tantalum capacitors instead of MLCC for 7660 if those are what's singing. Although it should be ~10kHz so it's likely LDO problem. HT75A0-1 LDO although not explicitly stated, from datasheet application circuit looks like it is not compatible with using MLCC output capacitor (C78), so it may oscillate and MLCC may sing in such case. My suggestion is to replace C78 with 10-22 uF tantalum capacitor. Also if C79 is more than 0.1uF, it's better to remove it. Using MLCC with incompatible LDO is a common engineering mistake.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 17, 2025, 05:45:24 pm
content: Quote from: wraper on February 17, 2025, 05:08:15 pmThat helps, thanks a lot! I'm beginning to understand how this works: 12V in > LDO > 10V > Charge Pump > -10V.According to the data sheet of the HT75A0-1, it wants 10µF polarized caps too, so if I replace all 4 of them - C53 & C54 for the ME7660 and C49 & C78 for the LDO, thats what you are suggesting? Certainly according to the data sheets for both of them. I wonder what the smaller 0604 caps (C50 & C79) are there for, decoupling maybe?

author: wraper
author_rank: Unknown
timestamp: February 17, 2025, 06:01:11 pm
content: I don't think replacing 7660 capacitors is really worth it unless C78 does not help. But it won't hurt either. The thing with MLCC is that they lose capacitance under voltage bias, so tantalum may be better there as you'll get more real capacitance with the same capacitance rating.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 17, 2025, 06:19:33 pm
content: OK, thanks again. Looking at the datasheet of tantalums right now, apparently they are a different form factor and bigger than 0805. The smallest one I can get quickly is only rated for 16V, is that enough head room at +12V supply? 20V ones are a little bigger and those may not fit.

author: wraper
author_rank: Unknown
timestamp: February 17, 2025, 06:34:15 pm
content: For usual tantallum at least 50% voltage rating margin is a must. But it's fine to use tantallum polymer near max rating.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 17, 2025, 08:39:23 pm
content: Then I will have to use wired versions because a C-size case which appears standard for 25V is 6mm long and doesn't fit on a 0805 footprint.

author: wraper
author_rank: Unknown
timestamp: February 17, 2025, 09:09:43 pm
content: If you use wired part, then you can use usual aluminum electrolytic. 20V tantalum will be fine, especially as you need only one. The thing with SMD tantalum is that they get wounded during soldering. They have a self healing mechanism, but when used at high voltage, they will have high failure rate as quite a bit may fail short instead of healing properly. There is no such problem with tantalum and aluminum polymer, aluminum electrolytic.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 17, 2025, 09:19:44 pm
content: At least for a test I'll use electrolytics, for a test that should work. Not sure if that's a good permanent solution because they hang upside down (the board is facing downwards normally). Maybe I get some of this while glue that is often found in power supplies to keep the components from moving.

author: ptluis
author_rank: Frequent Contributor
timestamp: February 18, 2025, 02:16:19 pm
content: C79 has a bad solder on the IC side, you should check carefully all soldering on the dc-dc circuit.Soldering on that dc-dc circuit looks really shitty

author: hp3310a
author_rank: Regular Contributor
timestamp: February 18, 2025, 02:31:49 pm
content: Replacing the caps for the LDO, including the stacked cap, brought almost complete success. There remains a faint noise at the same frequency that I can't really pinpoint the source of, maybe the small 603 caps C49 and C79 - cant really tell.I also fixed the reversed polarity of the leftmost one I soldered yesterday. The voltage on the -10V test point is only -8V, so not sure what this means in terms of functionality of the board. The -10V rail is used for the FET-input opamps, so they not really secondary I guess but I have no idea how these things work and how critical the -10V really are.The removed stacked cap had a capacitance of about 25µF-40µF combined, so the replacement is a lot less at 10µF, not sure if that would bring down the voltage further towards -10V.The reversed ET5411 schematics from morris6 (https://www.eevblog.com/forum/testgear/east-tester-et5411a-(and-et5410a)-electronic-load-schematic-reversed/msg4882754/#msg4882754) put the ME7660 caps at 47µF and the output cap on the LDO at > 22µF. All except the stacked one were 10µF on my board. All those values are way beyond what the data sheets for ME7660 and the LDO say is "common".I'll turn in on and load it a little to see how it behaves.

author: wraper
author_rank: Unknown
timestamp: February 18, 2025, 05:10:47 pm
content: Quote from: hp3310a on February 18, 2025, 02:31:49 pmI see another 3x of AMS1117 LDO incorrectly used with MLCC on the output as well. They may oscillate too. You can check it with oscilloscope.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 18, 2025, 08:46:32 pm
content: With the unit completely closed I can't hear the offending high-pitch noise any longer - in part thanks to the fan that's always on. So yeah, problem solved! I guess I'll leave it at that.When the tantalums I ordered arrive I will replace the electrolytics, maybe for higher capacitance versions. I managed to find case-B types, those might fit the 805 footprint if I'm lucky. I can choose from 10µF, 22µF and 47µF.I did run a short test with up to 10A at 20V and the device didn't seem to mind the weak -10V rail, at least I didn't notice a malfunction.

author: ptluis
author_rank: Frequent Contributor
timestamp: February 19, 2025, 04:24:02 pm
content: Quote from: hp3310a on February 18, 2025, 08:46:32 pmAs I told you a few posts back, the factory soldering is shitty,You should inspect all soldering on the board with an microscope. Why I'm insisting on this? because I bought two units from them, 1CH and 2 CH models. The 1CH model had the same problem as your unit and after inspecting carefully on the microscope I've found a large number of bad solder joints specially on caps. After a resoldering task The unit become 100% functional. On the 2 channel model, the unit become excessively unstable when tested something above 1A, I then decided to inspect the soldering, since this unit contains 2 smps power supplies instead of a transformer, on one of the smps there was some cold joints on the caps and Ic. On the main board I've found some cold joints also and had to redo all the connections from pcb to the binding posts, on the binding posts the nut wasn't tight enough to make a proper connection. I conclude that factory soldering and qc is shitty.

author: hp3310a
author_rank: Regular Contributor
timestamp: February 19, 2025, 08:25:02 pm
content: Quote from: ptluis on February 19, 2025, 04:24:02 pmYes, thanks, I saw your comment but forgot. I can definitely confirm the soldering is questionable. All the caps that I took off had burned flux (or something else that was burned) on the underside, adding a layer between pad and the component. So something might have happened there in production.Do I understand you correctly, you had the same high-pitched noise and resolding all components fixed it? If so, did you take them off, with cleanup and completely resoldering them or did you just reflow using a hot air station or soldering iron?

author: ptluis
author_rank: Frequent Contributor
timestamp: February 20, 2025, 03:51:38 am
content: Quote from: hp3310a on February 19, 2025, 08:25:02 pmOn the 1Ch unit the high pitch did exists when i first tested and also some instability of the device. Resoldering did solve all problems. I resolder everything with amtech flux and low melting temperature lead solder. I only clean old solder in the situation were there's excessive solder on the joint or if the soldering doesn't look nice. I didn't remove any components. the 2ch unit was a little more time consuming because it had several defects, but also solved by resoldering. Always check the nut in the biding posts, check for proper resistance connection between the biding post and pcb, move the wires and check is the measure resistance changes, that's how I detected a micro gap between the wire terminal/washer/nut, this micro gap creates fake voltage drop on the display measurement, giving the wrong idea about the dut

author: wraper
author_rank: Unknown
timestamp: February 20, 2025, 04:00:34 am
content: ^your fixes might not last. Quite likely you just re-heated MLCC which restarted their capacitance ageing process, and problem might return once their capacitance drops to the previous level. Mixing leaded and lead-free solders results in a shitty alloy. It's best to use SAC305 or SAC307 for SMD solder joints or dull TH joints and SnCu solders for shiny TH joints (no silver). Solder joints on hp3310a's photos look good enough.

author: ptluis
author_rank: Frequent Contributor
timestamp: February 20, 2025, 11:19:10 am
content: Quote from: wraper on February 20, 2025, 04:00:34 amWhat you mean won't last, days, months, years? Let me tell you that i have equipments repaired with mixed lead and non lead solder and they keep perfect for decades, lead free solder crack easily than leaded solder, lead solder hold on better in situations were thermal stress is higher, and support some flexibility of the pcb better. But anyway solder joints won't last for ever, but lead free solder crack faster.Concerning the units mentioned they were repaired a few years ago when they first launch them in the market, and continue to operate 100% on a daily base, so no worries. Anyway caps used on Chinese electronics are bad quality and they will fail in a short period of time, when it happens, i replace them with good ones.And btw one thing i learn in my life is to always inspect soldering on any Chinese device, known or unknown brand.

author: wraper
author_rank: Unknown
timestamp: February 20, 2025, 01:43:24 pm
content: There are different lead-free solders. Some are softer than 60/40, others harder. Most of them have higher tensile strength than 60/40. It lasting afterwards does not mean it's good, likely just that it was in mechanical stress free environment. Anyway, solder joint cracking is not really an issue on 2+ layer PCBs with plated vias. It's a big issue on single layer PCBs though.

author: ptluis
author_rank: Frequent Contributor
timestamp: February 20, 2025, 02:25:41 pm
content: Quote from: wraper on February 20, 2025, 01:43:24 pmI agree with that but let me add this, do you know what are the most common defects on ECU that I repair? cracked non lead solder on IC pins or capacitors, since ECU units are subject to all kind of vibrations, non lead solder crack really fast, on older ECU units with lead solder it's rare to find one with a cracked solder, and I'm talking about Bosch ECU. I'll give you another example, Audi,Seat,Skoda all the VAG group had serious problems with climatronic units specially early models, this includes radio units, air conditioner, clima control, whippers, etc, due to cracked non lead solder or corroded pcb tracks. On Fiat and other brands with problems with electric steering wheel cracked non lead solder were the most common problem. So switching to non lead solder, (i know environment thing) was a bad thing for auto industry. Sensors, relays, and all kind of auto electronics suffer from that. 90% of the times is enough to solder with leaded solder and the thing won't return to the shop. And I don't believe that outsourced companies that cooperate with auto brands are using low quality solder. From my point of view, technically corrected or not, the harder the solder the lesser time it lasts specially if subjected to vibrations, thermals and all kind of stress environment. sorry for any mistakes but I'm writing from my phone and my eyesight is not what use to be nor my fingers

author: hp3310a
author_rank: Regular Contributor
timestamp: March 08, 2025, 04:50:31 pm
content: So the tantalum capacitors arrived, I ordered a couple of case size B and size A types. Case size A would fit better but they only go to 10µF.The LDO output capacitor (the stacked one) was about 47µF in total, so that needed to stay the same. Also the voltage converter seems to require higher capacitance (the reversed ER5411 schematics show 47µF on the output), so I decided to make those 47µF too. The LDO input was going to be a 22µF in agreement with the schematics. Originally those were all 10µF ceramics except the stacked one.So, first desoldering of the temporary electrolytics (sorry for the over-exposure, the microscope camera doesn't want as much light as I do).Good it was the GND pad that got ripped off, the other one would have been much more difficult to replace. I scratched me a new one on the opposite side.Then wicked up the pads, cleaned the surroundings with IPA and hot-aired the new capacitors on. Certainly not ideal but I think they all attached well.I then let the unit run under load for 30 minutes at 15V/25A. Seemed to work fine, the voltages on the test points around the converter were all a bit nearer to the design values than before, so I guess - at least in the short term - it's a success.

author: ranma
author_rank: Newbie
timestamp: March 26, 2025, 08:39:23 pm
content: Maybe swapping the ME7660C for an LTC1044A could be an option, the latter can switch at inaudible frequencies, with the frequency determined by V+ and a Cap on the OSC pin, pinout seems to be drop-in replacement otherwise (except for pin 1, which is fOSC boost instead of NC).

author: hp3310a
author_rank: Regular Contributor
timestamp: March 27, 2025, 06:00:47 pm
content: Could be an option, but if I read the data sheet right, the default frequency is 5kHz, should be audible even better. Of course less annoying. However, the datasheet also says:QuoteSo you will have to exchange the capacitors, too. The ME7660C data sheet also says polarized capacitors, it was East Testers clever idea to use ceramics instead.

author: wraper
author_rank: Unknown
timestamp: March 27, 2025, 06:17:25 pm
content: Capacitor type is not critical for 7660 as it does not rely on ESR.

author: hp3310a
author_rank: Regular Contributor
timestamp: March 27, 2025, 06:28:18 pm
content: Quote from: wraper on March 27, 2025, 06:17:25 pmYou may want to re-read your own comments on page 1.

author: wraper
author_rank: Unknown
timestamp: March 27, 2025, 06:32:17 pm
content: Quote from: hp3310a on March 27, 2025, 06:28:18 pmI don't need to reread it. There is a chance MLCC may sing but it won't affect operation. That's why I said you don't to change them if changing just LDO capacitor helps. On other hand, LDO MLCC may sing if it causes LDO oscillation which must not be there if circuit operates properly.

author: hp3310a
author_rank: Regular Contributor
timestamp: March 27, 2025, 07:34:14 pm
content: Quote from: wraper on March 27, 2025, 06:32:17 pmThe whole point of this entire thread is the noise those capacitors make, so it very much is about exchanging the capacitors to polarized ones.

author: wraper
author_rank: Unknown
timestamp: March 27, 2025, 08:15:53 pm
content: Quote from: hp3310a on March 27, 2025, 07:34:14 pmThen if they're actually not making the noise, what's the point of changing them? You changed them altogether without figuring out if there was a need to change 7660 capacitors to begin with.Quote from: wraper on February 17, 2025, 06:01:11 pm

author: hp3310a
author_rank: Regular Contributor
timestamp: March 27, 2025, 09:00:59 pm
content: Quote from: wraper on March 27, 2025, 08:15:53 pmThey did make noise. It was a chorus with the ones for the LDO.

author: ranma
author_rank: Newbie
timestamp: March 30, 2025, 07:15:43 pm
content: A very MacGyvered solution with mostly parts I had lying around (I did wrap the STM32 in Kaptan tape before closing things back up):First tried replacing C54 with a tantalum cap and adding additional capacity on the output in parallel to C53, this seemed to lower the noise somewhat to be less grating, but not sufficient enough.After reading the ME7660C datasheet again I decided I should try injecting a higher clock into the OSC pin (which should be double the switching frequency) and went with 50kHz generated by an STM32G0 and now its quiet to my ears at least (with the fan unplugged for testing).

author: wraper
author_rank: Unknown
timestamp: March 30, 2025, 07:22:19 pm
content: Quote from: ranma on March 30, 2025, 07:15:43 pmReplace C78 and maybe a few other MLCC instead of bodging this nonsense.

author: ranma
author_rank: Newbie
timestamp: March 30, 2025, 07:25:10 pm
content: Quote from: wraper on March 30, 2025, 07:22:19 pmIts not nonsense if it worksBut yes, at the very least this should be cleaned up and have shorter leads to generate less EMI. I know why I did say "MacGuyered"...Attached datasheet note about driving OSC externally "due to noise"

author: wraper
author_rank: Unknown
timestamp: March 31, 2025, 01:28:37 am
content: Quote from: ranma on March 30, 2025, 07:25:10 pmIt's like installing boat anchor to a car when its handbrake fails.

author: hp3310a
author_rank: Regular Contributor
timestamp: April 01, 2025, 09:25:06 am
content: Quote from: ranma on March 30, 2025, 07:15:43 pmIf it works and fixes the problem, great! Thanks for showing, even if it's not 100% pretty.