PIE675T01E/09 induction hob fault c3 - Page 1
Forum section: electronics / repair

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 16, 2021, 07:41:29 pm
content: I haven't been involved in electronics for donkey's years but I don't have the moneyfor a new hob and was hoping I could repair it.Maybe someone can give a clue how to try to find the cause of the fault c3 .I called Bosch and asked what c3 means as I couldn't find the fault code anywhereand they told me it indicates overheating. I tried switching power off/on but it made no difference(fault occurred again).The PIE675T01E/09 hob has 4 plates: front and back left pair and front and back right pair and 3 pcb's , oneunder each of the two pairs of plates and one in the front for the buttons.The two plates on the left work without faults.The two plates on the right work such that if you set them to a low heat value (max is 9, low is somewhere around 3), they almost immediatelystart flashing the fault code. If you turn them on to a higher value, they will work for a few seconds and start flashing the fault code.If you turn the hob off, you can again try setting the temperature and the fault occurs again.I have opened the hob, disconnected the plates, thermistors and mains power, removed the right pcb(I presume the right pcb is associated to the two right plates which cause thefault code to appear) . It is a Siemens 9000 156 089 ELIN-DCHA ADV pcb. On initial inspection, I don't see any visibledamage anywhere except the mica on top of one of the two plates causing the fault has a slight haze on it (nothingout of the ordinary).All the 4 thermistors on the plates read some 60kohm and reduce in value when heated with hair dryer and return to this valueafter some time. All of the plates read a fraction of an ohm.So, I guess I'm "lucky" not to have an "easy" fault to find.

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 16, 2021, 08:14:26 pm
content: sorry something weird is going on with the saving and removing of the message, so there is a duplicate message/thread- I triedto delete the older message/thread (without attachments) but nothing happens. I will write only in this thread.

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 16, 2021, 08:19:58 pm
content: One other bit of information which may be of interest - the fan seems to be on for a long timealthough there is no overheating (at least not from the plates as they cause the fault quickly)

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2021, 09:27:46 pm
content: I can't see anything in the photos but is there a thermistor sensing the heatsink temperature? Just a thought.Also maybe check the soldering / integrity of all high current joints.

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 17, 2021, 08:37:45 pm
content: Here's an initial search for possible fault sources which are directly related to overheating(my initial thinking is that it could be a fault with the IGBT drive circuit and there is anactual overheating or the circuitry doing the temperature measurement is not workingor both).(a)Two blue thermistors at line/power input next to the toroids and emi suppression caps.My first question is -does one do any testing with power connected and how sincewe're dealing with the induction plates/can't have them in place and glass in place ?How should I test these thermistors ?(b)There are four 20N60A4D IGBTs mounted on pcb top , under each of them on pcb bottom surface are 8 pin chips(see photo) A 3126 presume drive chipsfor which I cannot find datasheet. Anyone know what they are ?

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 17, 2021, 08:40:10 pm
content: There's a gazillion points marked as TSPnumber- I presume test points, anyone knowwhether it is possible to find any documentation for this pcb?

author: fzabkar
author_rank: Super Contributor
timestamp: January 17, 2021, 09:25:54 pm
content: I think that 8-pin part is an Avago HCPL-3126 IGBT gate driver.Here is the datasheet for the HCPL-3120:HCPL-3120, Avago, 2.5 Amp Output Current IGBT Gate Drive Optocoupler, DIP-8:https://www.mouser.com/datasheet/2/678/V02-0161EN_DS_HCPL-3120_2016-03-21-908803.pdf... and an image ...http://www.dnatechindia.com/image/cache/catalog/a3120-500x500.jpgI wasn't able to find the 3126 part on the manufacturer's web site:https://www.broadcom.com/site-search?q="HCPL-3120"This supplier ...https://ksp-electronics.com/en/products/1374693-integrated-circuit/a3126-dip-8... claims it is compatible with Toshiba's TLP350:https://www.glynshop.com/erp/owweb/Daten/Datenblaetter/Toshiba/TLP350_datasheet_en_20140922.pdf

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 17, 2021, 09:43:12 pm
content: I found this doc on scribd which may give some more info in case someoneexperienced is willing to give a pointer on how to proceed. The doc is not forexactly the same pcb but looks very similar.

author: fzabkar
author_rank: Super Contributor
timestamp: January 17, 2021, 10:00:01 pm
content: QuoteQuoteQuoteQuoteI wonder if the reference voltage for the "temperature sensor under the glass" is missing??

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 19, 2021, 09:01:55 am
content: A duplicate of this thread exists as something weird was going on when I created the thread.I have tried a number of times to delete the duplicate thread but nothing happens - I will try to deleteit again but anyway, this will be the thread that I will use.Here is a comment from the duplicate thread from fcb:Our AEG CIB6740 threw a hissy-fit literally a year and day after we bought it.Dismantled the hob and removed the two large PCB's. Turned out that the vents at the back of the top push out steam when using the oven and OH had placed a large tall pot on a back ring with cold water in it (unsurprising!), the steam 'diverted' was basically ended up condensing inside through a badly fitted bit of plastic, alumimium hose - ended up under one of the PCB's via a fan. This triggered a fault condition.Boards were carefully dried and cleaned, and it worked perfectly when reassembled.Not sure if this helps, but if you do have an induction hob/cooker that throws a hissy-fit, don't leave it as it might be moisture inside.

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 19, 2021, 09:38:14 am
content: I tried again to find documentation for my exact induction hob but to no avail. I came across two moredocs in case it helps for my case/anyone having similar probs in future (attached).Using the docs, in addition to the two thermistors in the power input stage (which I believe are used to limitinrush current) I see there are two SMD NTC's which measure the temperature of the IGBT's.With the information I have been given till now, I think I will try to check the NTC's, recheck if thetemperature sensors/holders which touch the glass are seating properly / touching glass (I am not very happywith the metal holder spring legs) , generally try to re-seat everything again in case I am luckyand this is alldue to excessive temperature/humidity/liquid from pots. After this, I will look into the reference voltage fortemperature sensor.A question ahead of time - how would I be able to do any testing/measurement on the live circuit egto check a reference voltage as I would need to remove the glass and coils to get to the pcb's ?

author: vjekobalas
author_rank: Regular Contributor
timestamp: September 03, 2021, 10:19:18 pm
content: I'd like to thank all that helped with input. I will need to let this waitas I have more serious things to solve and my wife purchasedanother hob.

author: benneton
author_rank: Contributor
timestamp: September 03, 2021, 11:42:01 pm
content: With induction hobs:1. Check IGBT/S2. Check Graetz diode bridge3. Check NTC and its pair resistor (you could have multiple of those: plate heat sensor, IGBT heat sensor, even diode bridge heat sensor) always check their pair resistors too. You can test it while device is on, however I recommend having isolating transformer for your safety and your equipment's sake. Just a friendly warning. NTC/PTC are almost always used in voltage divider setup. You don't even need to turn the device on. Set your multimeter to Ohm and check the resistance between one end of pair R to other end of NTC. Notice the resistance then warm it up with finger for e.g. - it should be changed resistance. Usually it is okay even if there is any resistance/conductivity. However, characterics could be changed due to overheating. Middle point should be in the around half of reference by default (if 5V => 2-3V). Ohm check could be enough, however, sometimes parts are behaving differently while device is on.4. Check buffer caps / all caps. Usually filter and electrolyte ones. If you have oscilloscope, check DC pins. No AC should be there.5. Check traces - very often discovering these types of errors - Trace the sensor path to MCU...

author: vjekobalas
author_rank: Regular Contributor
timestamp: September 04, 2021, 08:50:31 am
content: Thanks a lot! Will try all the points you mentioned and more seriously go through it all as soon as I have time

author: benneton
author_rank: Contributor
timestamp: September 04, 2021, 09:57:45 am
content: You are welcome!"If you turn them on to a higher value, they will work for a few seconds and start flashing the fault code" smells like igbt/graetz overheat protection. Tolerance could be greater on a higher power setting (software side) - device on boost will heat more, therefore some grace period. Look for a small ntc next to positive or negative pad of diode bridge or IGBT. Maybe, just maybe... Good luck and take care