Author Topic: Need help with Samsung NZ64H57477K Induction Hob repair (Read 5521 times)

flattermann1822 · « **on:** May 30, 2018, 05:28:08 pm »

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

bingo600 · « **Reply #1 on:** May 30, 2018, 05:43:27 pm »

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

wraper · « **Reply #2 on:** May 30, 2018, 06:23:30 pm »

Quote from: bingo600 on May 30, 2018, 05:43:27 pm

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

85^oC does not mean lousy, as well as 105^oC 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 105^oC.

wraper · « **Reply #3 on:** May 30, 2018, 06:27:10 pm »

If you don't have ESR meter to check them, try replacing this capacitor first.

bingo600 · « **Reply #4 on:** May 30, 2018, 06:40:03 pm »

Quote from: wraper on May 30, 2018, 06:23:30 pm

85^oC does not mean lousy, as well as 105^oC does not mean good .

How can you tell that .. You didn't see the brand of the caps i changed

And 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

wraper · « **Reply #5 on:** May 30, 2018, 07:39:08 pm »

Quote from: bingo600 on May 30, 2018, 06:40:03 pm

Quote from: wraper on May 30, 2018, 06:23:30 pm
85^oC does not mean lousy, as well as 105^oC does not mean good .

How can you tell that .. You didn't see the brand of the caps i changed

I 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" 85^oC caps. I just said that temperature rating does not tell anything about capacitor quality. Not to say that mentioning 85^oC 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

flattermann1822 · « **Reply #6 on:** May 30, 2018, 09:22:34 pm »

Quote from: wraper on May 30, 2018, 06:27:10 pm

If you don't have ESR meter to check them, try replacing this capacitor first.

thanks 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.

wraper · « **Reply #7 on:** May 30, 2018, 09:36:32 pm »

I hope you ordered low ESR type except big cap. General purpose 105^oC 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.

flattermann1822 · « **Reply #8 on:** May 30, 2018, 09:49:50 pm »

Quote from: wraper on May 30, 2018, 09:36:32 pm

I hope you ordered low ESR type except big cap. General purpose 105^oC 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.

Yes, 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 again

Gesendet von meinem HUAWEI VNS-L31 mit Tapatalk

flattermann1822 · « **Reply #9 on:** May 31, 2018, 06:08:27 pm »

Quote from: wraper on May 30, 2018, 09:36:32 pm

I hope you ordered low ESR type except big cap. General purpose 105^oC 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.

I did the test with load on the dc outputs. See attachment. Outputs are still not stable.

flattermann1822 · « **Reply #10 on:** June 01, 2018, 06:52:45 pm »

Quote from: bingo600 on May 30, 2018, 05:43:27 pm

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

I replaced the other electrolytic caps too, but still no stable output on 12V and 5V rails. What can I do next?

wraper · « **Reply #11 on:** June 01, 2018, 06:57:39 pm »

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.

flattermann1822 · « **Reply #12 on:** June 04, 2018, 08:21:20 pm »

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?

wraper · « **Reply #13 on:** June 04, 2018, 08:42:41 pm »

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

flattermann1822 · « **Reply #14 on:** June 09, 2018, 09:33:57 am »

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 again
What's the next i can check?

Shock · « **Reply #15 on:** June 10, 2018, 12:15:00 am »

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.

flattermann1822 · « **Reply #16 on:** June 10, 2018, 09:43:21 am »

I did some further load measurements, see attached document point 2.7.

I have already replaced all electrolytic capacitors with new low ESR ones.

wraper · « **Reply #17 on:** June 10, 2018, 09:58:37 am »

Yeah, IC501 might be dead, it should not overshoot 5V.

flattermann1822 · « **Reply #18 on:** June 10, 2018, 10:49:33 am »

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.

wraper · « **Reply #19 on:** June 10, 2018, 11:16:43 am »

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.

flattermann1822 · « **Reply #20 on:** June 10, 2018, 11:59:03 am »

Quote from: wraper on June 10, 2018, 11:16:43 am

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.

I replaced IC501 with TS7805CZ LDO but the waveforms are almost the same $:-\$

wraper · « **Reply #21 on:** June 10, 2018, 01:03:04 pm »

Quote from: flattermann1822 on June 10, 2018, 11:59:03 am

I replaced IC501 with TS7805CZ LDO but the waveforms are almost the same $:-\$

Does 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.

wraper · « **Reply #22 on:** June 10, 2018, 01:06:27 pm »

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.

Shock · « **Reply #23 on:** June 10, 2018, 02:06:04 pm »

Just curious what the pinout on the LVR you soldered in was.

flattermann1822 · « **Reply #24 on:** June 10, 2018, 02:29:30 pm »

Quote from: wraper on June 10, 2018, 01:06:27 pm

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.

Yes 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.


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Author Topic: Need help with Samsung NZ64H57477K Induction Hob repair (Read 5521 times)

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