Kitchen Chimney Circuit Board Failure

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
Hello folks,
my kitchen chimney has 4 buttons and 1 digit screen. 3 buttons for the fan 1 for the lamp , just Number 3 button works and sometimes the lamp switch on itself. I checked the capacitors the polyester one yellow and 220 uf 10v seems faulty for now , I m gonna desolder them and measure again,
what are your thoughts
thanks in advance
respect from Turkey
 

Attachments

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
Looks like something has blown, or is it a Capacitor or Led?
Check out the voltages shown.

View attachment 271720
Dude the one you asked if burnt or not is not burnt
The biack rectangle component on the left is upper right leg is 19,14,5 V dc bottom right leg is 4,95V dc and the one on the right in the middle is zero, no voltage. Thre black rectangle component on the right you pointed is 19, 16 V dc then 1.
 

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
By the way I desoldered those 3 capacitors and measured them with ut33a+
Results :
Yellow polyester 0,33 uf = 0,33 uf

470uf 25V = 0,441 mf =441 uf

220uf 10V = 0,26 mf = 260 uf
So are 470uf and 220uf caps broken? Should I replace them and problem is solved?
Thanks in advance
B9539CD7-85A6-4024-815E-4CC7FD4D41AD.jpeg
 

Dodgydave

Joined Jun 22, 2012
10,394
So the 3 pin device is a 5V regulator, the black rectangular object is a Diode , the psu uses a Half wave rectifier and two smoothing capacitors, so if the 5V is there then there's nothing else i can suggest only to replace the capacitors.
 

LesJones

Joined Jan 8, 2017
3,773
Your electrolytic capacitors are within the typical wide tolerance that you would expect fo an electrolytic capacitor.
I agree with Dave that you should check the voltages at the input (Top pin on your picture.) and output (Bottom pin on your picture.) pins with respect to the center pin of the voltage regulator which is common negative. I expect the input to be about 16 volts and the output probably 5 volts. (I am guessing at 5 volts as I can't read the part numbers of the ICs on your picture. Can you tell us the part numbers of the ICs ?

Les.
 

LesJones

Joined Jan 8, 2017
3,773
One thing you could check before applying power to the board to do the voltage test is to measure the resistance of the primary and secondary windings of the transformer. Many small transformers have a thermal fuse embedded into the windings which is connected in series with the primary winding. This may have failed. If the fault is not related to the power supply components then the only hope is that the ULN2003 has failed. If the microcontroller ( Holtek device.) has failed (Which is unlikely.) then it is very unlikely that you would be able to obtain the code to program a new one.

Les.
 

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
Sir, hi there
I have received the new capacitors and Lcr T4 tester.Before I soldered them , I wanted to measure the new capacitors and the old capacitors just to make sure.
Results:

Polyester Old one 0,33 uf 275 V= 333,5 nf Esr 7 ohm

Polyester New one No farad stated and bigger than the original in size =929,2nf Esr 2 ohm

Old one 470uf 25V = 429,8 uf Esr 0,29 ohm Vloss: 1,6%

New one=458,3 uf Esr 0,27 ohm Vloss:0,9 %


Old one 220uf 10V =233,4uf Esr 0,67 ohm Vloss:4,8%

New one:211,3 uf Esr 0,65 ohm Vloss: 2,2%

So the new polyester one doesn t have the equal values with the original one? I mean they sent me the wrong polyester capacitor?? Or I can use the new one as a replacement?

The other two capacitors I mean the old ones were faulty so the new ones arw ok ? Please help me out

Best Regards


So the 3 pin device is a 5V regulator, the black rectangular object is a Diode , the psu uses a Half wave rectifier and two smoothing capacitors, so if the 5V is there then there's nothing else i can suggest only to replace the capacitors.
 

Attachments

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
Yes sir , it is like you said. Should I use it or find a new one identical to the original which is 0,33 uf?
By the way the old polyester cap has Esr 7 ohm , is Esr 7 ohm too much, does it mean it is broken?

Respect

The New polyester cap is a 1uF one , it's going across the mains input .
 

Dodgydave

Joined Jun 22, 2012
10,394
You can use it as long as the voltage rating is 375V or higher,esr rating is the internal resistance of the capacitor, the lower the resistance the better, as less wastage.
 
Last edited:

Thread Starter

torukojinnn

Joined Jul 16, 2022
43
Yes you can use it.
Dear Sir , I changed the three caps and not much changed ,It is still the same. I measured some points you previously told me to do. Please check the photos7CF90302-6252-497C-83D2-2D687A00197F.jpeg

what do you think ? IC units are ok?

And by touching the black probe of multimeter to the negative leg of capacitor with red probe I checked the pins and the dc voltage value not changed. It is as you can see in the photo.21F0E223-CDC7-4891-8847-2F774EB9B70E.jpeg
the blue pin belongs to buttons there are 5 couple of pins but just one gves me 2.48 v dc the rest gives nothing
nothing changed, should I desolder the relays and check them all one by one?
or you can suggest me sth else?
Thanks again
 
Top