Need help with Samsung NZ64H57477K Induction Hob repair - Page 1
Forum section: electronics / repair

author: flattermann1822
author_rank: Contributor
timestamp: May 30, 2018, 05:28:08 pm
content: My induction hob doesn't work anymore.The hob doesn't switch on when touching the power button. No response. No LEDs or something lights up.I guess i found something abnormal on the power supply pcb. Fuses are ok but 12V are not stable and 5V are low with some peaks. More see attached scope pics.1. Is this normal?2. What can cause such effects?3. Do someone know where to find shematics or part information?4. Where can i buy a replacement?Thanks

author: bingo600
author_rank: Super Contributor
timestamp: May 30, 2018, 05:43:27 pm
content: I have saved 2 induction hubs w. touch , for a couple of friends.By just blindly replace all Electrolytic caps.And use 105 deg instead of the lousy 85 dec caps in the replacement./Bingo

author: wraper
author_rank: Unknown
timestamp: May 30, 2018, 06:23:30 pm
content: Quote from: bingo600 on May 30, 2018, 05:43:27 pm85oC does not mean lousy, as well as 105oC does not mean good. Not to say, all electrolytic caps except big high voltage cap seem to be LOW ESR type and of all are rated for 105oC.

author: wraper
author_rank: Unknown
timestamp: May 30, 2018, 06:27:10 pm
content: If you don't have ESR meter to check them, try replacing this capacitor first.

author: bingo600
author_rank: Super Contributor
timestamp: May 30, 2018, 06:40:03 pm
content: Quote from: wraper on May 30, 2018, 06:23:30 pmHow can you tell that .. You didn't see the brand of the caps i changedAnd the Touch PSU PCB was just under the cooking plate, getting a lot of radiated heat.Weird comment ...The one where you actually suggests something was way better./Bingo

author: wraper
author_rank: Unknown
timestamp: May 30, 2018, 07:39:08 pm
content: Quote from: bingo600 on May 30, 2018, 06:40:03 pmI did not say anything about caps you changed. And you did not even say about what caps you replaced in your repairs but said to replace "lousy" 85oC caps. I just said that temperature rating does not tell anything about capacitor quality. Not to say that mentioning 85oC is not even applicable to this case as there are none of such present on the PCB.https://www.samyoung.co.kr/download/new/NXA.pdf

author: flattermann1822
author_rank: Contributor
timestamp: May 30, 2018, 09:22:34 pm
content: Quote from: wraper on May 30, 2018, 06:27:10 pmthanks for your reply.i don't have ESR meter. So I replaced CP04 (47uF/50V/105°C) with no success. I ordered the other electrolytic caps and will replace them too.

author: wraper
author_rank: Unknown
timestamp: May 30, 2018, 09:36:32 pm
content: I hope you ordered low ESR type except big cap. General purpose 105oC capacitors won't last. Now rethinking about those waveforms, did you capture those while PSU was disconnected from the rest of the circuit? It may fail to work properly without any load attached. SMPS needs a minimum load and there does not seem to be any dummy load resistor present on the PCB.I would suggest to measure while it is connected to the rest of the circuit or attaching some dummy load to at least one of the rails. Something that would sink at least 0.5W, say <47R on 5V rail or <200R on 12V rail.

author: flattermann1822
author_rank: Contributor
timestamp: May 30, 2018, 09:49:50 pm
content: Quote from: wraper on May 30, 2018, 09:36:32 pmYes, i ordered low esr type caps.Yes, i did not attach any load to 12V and 5V rail. I will do the test tomorrow with load againGesendet von meinem HUAWEI VNS-L31 mit Tapatalk

author: flattermann1822
author_rank: Contributor
timestamp: May 31, 2018, 06:08:27 pm
content: Quote from: wraper on May 30, 2018, 09:36:32 pmI did the test with load on the dc outputs. See attachment. Outputs are still not stable.

author: flattermann1822
author_rank: Contributor
timestamp: June 01, 2018, 06:52:45 pm
content: Quote from: bingo600 on May 30, 2018, 05:43:27 pmI replaced the other electrolytic caps too, but still no stable output on 12V and 5V rails. What can I do next?

author: wraper
author_rank: Unknown
timestamp: June 01, 2018, 06:57:39 pm
content: Hmm, I looked on 5V waveform and it's really weird and only 160mV mean. Check that rail. Maybe diode is shorted or something like that.

author: flattermann1822
author_rank: Contributor
timestamp: June 04, 2018, 08:21:20 pm
content: I didn't read your post. But I really found out something strange with a diode in the 5V circuit.I have no Vf and Vr when testing it with diode tester. And its shorted in both directions.I didn't find a part for the replacement with the printed information. Which diode can I use?

author: wraper
author_rank: Unknown
timestamp: June 04, 2018, 08:42:41 pm
content: You wrote SB2100 yourself, this is a part number. You could use basically any Schottky diode with at least 2A 50V ratings.http://www.smc-diodes.com/propdf/SB2100%20N0154%20REV.A.pdf

author: flattermann1822
author_rank: Contributor
timestamp: June 09, 2018, 09:33:57 am
content: I soldered a new SB2100 Diode and now there is something to see on the 5V rail. But both rails are still not stable. See attachment.Outputs are loaded with 150Ohm on 12V and 47Ohm on 5V rail againWhat's the next i can check?

author: Shock
author_rank: Super Contributor
timestamp: June 10, 2018, 12:15:00 am
content: The 12V rail looks happier now without the short, does it look even better without the 5V loaded? IC501 could be a problem, the 5V rail is not being regulated properly. Plus the secondary filter capacitors are still suspect if a few years old.

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 09:43:21 am
content: I did some further load measurements, see attached document point 2.7.I have already replaced all electrolytic capacitors with new low ESR ones.

author: wraper
author_rank: Unknown
timestamp: June 10, 2018, 09:58:37 am
content: Yeah, IC501 might be dead, it should not overshoot 5V.

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 10:49:33 am
content: How can I find out a suitable replacement for IC501.Which kind of IC is this?I didnt find a part with the printed text on the IC.

author: wraper
author_rank: Unknown
timestamp: June 10, 2018, 11:16:43 am
content: It's some sort of 1117 series 5V LDO vreg in DPAK (TO-252) package made by a lot of manufacturers, though I don't recognize which one exactly. But it does not really matter. You could use 1117 from any manufacturer, say NCP1117DT50 from On semi or LM1117IDTX-5.0 from TI.

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 11:59:03 am
content: Quote from: wraper on June 10, 2018, 11:16:43 amI replaced IC501 with TS7805CZ LDO but the waveforms are almost the same

author: wraper
author_rank: Unknown
timestamp: June 10, 2018, 01:03:04 pm
content: Quote from: flattermann1822 on June 10, 2018, 11:59:03 amDoes it peak to 6V as well? Then there might be something wrong with how you are measuring. BTW 7805 is not suitable replacement because of much higher minimum voltage drop on it.

author: wraper
author_rank: Unknown
timestamp: June 10, 2018, 01:06:27 pm
content: OK, This waveform was quiet misleading. There are 2 high high peaks on 5V waveform which make voltage measurement wrong. There is something sketchy going on with either how you are probing or your scope. Enable bandwidth limit at least.

author: Shock
author_rank: Super Contributor
timestamp: June 10, 2018, 02:06:04 pm
content: Just curious what the pinout on the LVR you soldered in was.

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 02:29:30 pm
content: Quote from: wraper on June 10, 2018, 01:06:27 pmYes there was something wrong with my scope. Besides the peaks there was a dc offset which is not real.So after scope self calibrating and enable bandwith limit here the waveforms again. Still with 7805 and both rails loaded.Peaks on CH2 are caused by a bad probe, sorry.

author: wraper
author_rank: Unknown
timestamp: June 10, 2018, 03:36:17 pm
content: Did you attach the load after replacing the diode?

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 06:05:34 pm
content: Quote from: Shock on June 10, 2018, 02:06:04 pmTO220, more see attachmentQuote from: wraper on June 10, 2018, 03:36:17 pmYou mean the original load (system PCBs)? Yes i did attached it. But hob does not seem to work again. I did not connect sensors and coils at this time.

author: flattermann1822
author_rank: Contributor
timestamp: June 10, 2018, 06:07:45 pm
content: I did some further test with the desoldered LDO. In my opinion it still works.

author: Shock
author_rank: Super Contributor
timestamp: June 12, 2018, 06:17:53 am
content: This is what I would do. I'd not connect the actual load until the supply looked functional (it may be damaging the supply). The resistors however, as long as low current is the safer route.I'd replace the LVR and order a couple of the proper LDOs (as they fail in stupid ways).Resolder that transformer connection closest to the 5V input. Clean up the solder splashes and flux.I'd decide it if it was worth physically isolating the 5V and 12V from the feedback/error circuit and make sure it's perfect by pulling and checking the small caps for capacitance and DC resistance.With the 5V regulator and the 12V dual diodes out I'd measure resistance between the 5V input and ground. Swap the leads over and measure ground to 5V input. Then do the same on the 5V output to ground (both ways) and then check the 12V to ground in both ways. If the feedback/error circuit is isolated as well this should build confidence there is no weird stuff going on in the secondary (and you can always apply a DC voltage source to the PCB and test it).Then recheck the previously replaced diode and test the dual diodes.At this stage if nothing conclusive I'd install the new LDO and dual diode again and power the supply and take another scope measurement unloaded and loaded with a small current.If still getting 6V on the output of the 5V LDO with a small load I'd check the Y suppression caps between the primary and secondary. Then lastly start checking the components in the feedback/error circuit.An ESR meter (even a cheap one) would be handy to know how bad things were on those replaced caps.

author: flattermann1822
author_rank: Contributor
timestamp: June 12, 2018, 06:04:55 pm
content: Quote from: Shock on June 12, 2018, 06:17:53 amThank you for your reply. i will order new LDOs, a cheap ESR meter and try to work through the points.

author: wraper
author_rank: Unknown
timestamp: June 12, 2018, 06:08:18 pm
content: I don't think there is any issue with LDO. The problem was with crappy measurement, not IC.

author: Shock
author_rank: Super Contributor
timestamp: June 13, 2018, 12:34:29 am
content: Quote from: wraper on June 12, 2018, 06:08:18 pmI don't think the LDO is necessarily going to fix it. It could be the 5V input is voltage/ripple, or current sensitive and cheap to get a couple and use one as a replacement.The question is what shorted the diode. It appears from the oscilloscope measurement it's switching at around 8KHz with current issues.But anyway continue on Wrapper with what you think should be done next, I was only suggesting what I'd try.

author: flattermann1822
author_rank: Contributor
timestamp: July 12, 2018, 03:58:19 pm
content: Quote from: Shock on June 12, 2018, 06:17:53 amI resoldered transformer connection. Clean up the pcb and have some new LDOs hereQuote from: Shock on June 12, 2018, 06:17:53 amdual Diodes (DS01) and DS2 are fine and I have a cheap ESR Meter here.Quote from: Shock on June 12, 2018, 06:17:53 amDid you mean that I now desolder all caps, RS05,RS08 and RS11 to check that there is high resistance between 12V/GND and 5V/GND?I tried to create the circuit diagram of the secondary. Not sure if TR1 and ICS02 have the correct symbols. At the moment ICS01 and DS01 are not mounted.

author: Shock
author_rank: Super Contributor
timestamp: July 13, 2018, 02:38:00 am
content: Last diagnosis was it looks to be either the circuits being pulled down or still suffering from a regulation issue. The 6V out of a 5V regulator is a concern because between ground and out should read 5V.By measuring between the rails and ground you can determine if a low resistance path exists which could be loading the output. The other idea is to isolate the transformer and feedback circuit and inject DC or AC to check the regulation, in a similar way that you did it out of circuit. Or check component by component. When the regulators or diodes are out it allows you to easily measure the input side of the regulator to ground or the output side to ground.To put it clearer, not a lot of components in that circuit should be drawing sizable current to ground, only the regulator which has to do it in order to lower the voltage. Aside from the diodes it's just the resistors in the feedback circuit.Check the Y suppression caps (marked CY01 CY02) as well.Confirm DC regulation is perfect, confirm secondary components not applying adverse load or affecting feedback, confirm optocoupler is functioning correctly and affecting switcher. Confirm switcher and flyback is performing within spec.

author: flattermann1822
author_rank: Contributor
timestamp: July 13, 2018, 04:17:33 pm
content: So I think the 6V never exist. My scope showed a DC-offset which is not real. The waveform below shows the actual measurement

author: Shock
author_rank: Super Contributor
timestamp: July 13, 2018, 08:03:34 pm
content: Assumed you put the load back on both outputs for that reading as the 12V is showing pulled down or weak. So the 5V is actually low in that case. Same deal if you want to check everything on the output.Please also pull and measure the current sense resistor on the primary RP03 - 0.7 ohms 1%, then do the snubber resistor RP01 - 4.7k Ohms 5%? If I have read those correctly, which sounds about right.Your multimeter might have problems with the first one as it's a low resistance so you could try the ESR tester. If those resistors drift it can cause output issues.

author: larsmtb
author_rank: Newbie
timestamp: January 05, 2021, 01:42:23 pm
content: Hello,I've got the same induction hob (NZ64H57477K) and it won't power on too. Unfortunately I don't own an oscilloscope but a quick measurement with my multimeter showed 0V at the 5V output voltage of the power supply pcb and 10V at the 12V output. But everything without load.@flatterman1822 did you successfully fixed your hob?Greetings from Germany

author: flattermann1822
author_rank: Contributor
timestamp: January 05, 2021, 02:41:00 pm
content: no, i didnt

author: larsmtb
author_rank: Newbie
timestamp: January 05, 2021, 06:03:37 pm
content: Too bad! What else have you tried?I put a load to the 5V output but also no voltage and no current. The 12V output collapses under load.PS: Grüße

author: larsmtb
author_rank: Newbie
timestamp: January 23, 2021, 06:08:43 pm
content: So I replaced the diode with this one:https://www.reichelt.de/schottkydiode-100-v-2-a-do-41-stps-2h100-p95386.html?&trstct=pos_0&nbc=1and CS03 with this one:https://www.reichelt.de/elko-radial-100-uf-35-v-105-c-low-esr-aec-q200-rad-fc-100-35-p84619.html?search=rad+fc+100%2F35and now everything is okay! I've got clean 5V and 12V at the output and after putting it back into the Induction Hob, everything is fine.