PSU Blown components identification

JMeth

Joined Jul 7, 2018
2
Hi all,

I found this forum when I was searching for a possible fix for my mom's Philips HD9240.

The two green-coated resistors, two 10uf capacitors and the Viper16L IC are (partly) burned.

Since I own the exact same airfryer as my mom, I was able to check those to see the color code of the 4-band resistors: orange/orange/black/gold -> 33 ohm 5%. Checked it with a multimeter and that gives me 33 ohm as well.

But I still have 3 questions:

1. - Sorry for my ignorance, but what is the "type of resistor" that I need? Carbon film or metal film? (I know tan coated can be an indication that it's carbon film and blue coated for metal film. But green coated can be anything?)

2. - I've read that this PSU has a Viper16L IC. The only VIPER16L IC with 7 legs that I can find on STMicroelectronics website is the Viper16LN. Is that the one I need?

3. - Someone said he replaced the caps with 10uf 50v ones, but on the caps on my PSU board is written: 10uf 400v. Is there any specific reason to use 50v instead of 400v?

Does anyone has an idea?

(P.S. The photo I've added is of the PSU board that belongs to my own airfryer (so not the faulty one). I Thought it might be useful in case anyone wants to know the color banding of the resistors etc.).

(P.P.S. Sorry for my broken English, it's not my native language.)
 

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Dodgydave

Joined Jun 22, 2012
8,592
Yes the resistors are 33ohms 5%, use metal film same wattage or higher. You can go higher in voltages with capacitors it's safer, Not Lower!!
The Viper chip is the same, the L is for 60Khz operation, H is for 115Khz.


Looking at your circuit, it's using the Isolated Supply regulation, with resistors R4, R6 as the voltage reference feedback, and using the blown capacitor as its smoothing supply via D1,D2.

Here is the datasheet.

https://www.st.com/en/power-management/viper16.html
 
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JMeth

Joined Jul 7, 2018
2
Thank you for helping me out, it's very much appreciated.

I'm going to order the Viper chip, the resistors and the capacitors.

I've read that Airfryer builds of 2015 and earlier need both the PSU board, as the display unit to be replaced, even if the latter one isn't broken. Philips doesn't explain why, but I suspect that older builds lack a coating to protect it against moist/heat/greas. The new displayunit (ref. nr. 420303616581) is explicitly being advertised as 'assy coated'.

As for now the display unit is still working (I've tested it), but I'm worried that the display unit and PSU board remain vulnerable for moist/heat/greas without a protection layer/coating. So as soon as the Viper, resistors and capacitors are being replaced, I'd prefer to spray a coating on the parts. What kind of spray would you advise for that job?
 

Steven David

Joined Jul 23, 2018
1
Hi all...im steven from singapore...just wanted to give a shout out to all in this thread for your very valuable tips...i followed ur steps n parts. And managed to successfully repair my unit...THANK U SOOO MUCH GUYS!!
 

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tvdwouw

Joined Jun 1, 2017
2
Hi Guys,

I am trying to repair the PSU on two Philips Airfryers HD9240 - I have looked for the schematics online but cant find anything. One of these units is my own and one with the exact same fault on a friends. Naturally both just out of warranty.

I have narrowed it down to two blown resistors and a 50v 10uf capacitor. One of the boards a Viper 16L IC has cracked as well, I suspect from the heat when the capacitor went, so will be replacing them on both boards as well.

The capacitor and the IC are easy enough to identify, the issue I am having is trying to identify the correct replacement resistors. On both boards they are blackened and cracked open. I cannot make out all the colours, they both start with brown and end with gold. the rest I am not sure of, if it is discolorationdue to heat or not, also not sure if they are 4 or 5 band resistors - depending on the light you look under, it could be either. I tried measuring them on a DMM but they are dead.

unfortunately I do not know enough about circuit design to be able to work out what is needed.

If anybody has repaired one of these before or knows where I can get hold of the schematics it would be greatly appreciated - or if there is a way to work out the value of the resistors... (I have seen some articles on scratching off the insulation and trying to measure it that way so might go down that route)

Please see pics of board and resistors.

thanks in advance!
-Mike
 

joshuadoh

Joined Jun 4, 2019
2
Dear Meadow,

Mine is faulty as the same as your one. But I don't know how to disassemble to take out the power board.
If you let me know how to do this, it will be appreciated.

From the UK, Joshua,
 

joshuadoh

Joined Jun 4, 2019
2
Dear Meadow,

Mine is faulty as the same as your one. But I don't know how to disassemble to take out the power board.
If you let me know how to do this, it will be appreciated.

From the UK, Joshua,
Disassembly was done after downloading the service manual. Thanks for tvdwouw.
By the way, is Viper 16LN compatible with 0951 LNK3649N 69212C?
 

syed1979

Joined Mar 19, 2019
4
Hi Guys,

I am trying to repair the PSU on two Philips Airfryers HD9240 - I have looked for the schematics online but cant find anything. One of these units is my own and one with the exact same fault on a friends. Naturally both just out of warranty.

I have narrowed it down to two blown resistors and a 50v 10uf capacitor. One of the boards a Viper 16L IC has cracked as well, I suspect from the heat when the capacitor went, so will be replacing them on both boards as well.

The capacitor and the IC are easy enough to identify, the issue I am having is trying to identify the correct replacement resistors. On both boards they are blackened and cracked open. I cannot make out all the colours, they both start with brown and end with gold. the rest I am not sure of, if it is discolorationdue to heat or not, also not sure if they are 4 or 5 band resistors - depending on the light you look under, it could be either. I tried measuring them on a DMM but they are dead.

unfortunately I do not know enough about circuit design to be able to work out what is needed.

If anybody has repaired one of these before or knows where I can get hold of the schematics it would be greatly appreciated - or if there is a way to work out the value of the resistors... (I have seen some articles on scratching off the insulation and trying to measure it that way so might go down that route)

Please see pics of board and resistors.

thanks in advance!
-Mike
Hi, may I know the type of D1 I should use?
 

syed1979

Joined Mar 19, 2019
4
Hello, thanks to you all for the information above it is invaluable. I have an airfryer with the same problem, same PSU. Both resistors are blown, cap looks OK, rectifier looks OK. the chip is difficult, it looks odd, maybe a burn on the top but no sign of any issues around the pins. The unusual thing is on the board underside smc diode D1 is destroyed completely. Can anyone help me with a part number for this item. It is only quite small compared to the other diodes.
 

Dodgydave

Joined Jun 22, 2012
8,592
Looking at the circuit diagram on the datasheet, the diode is connected to pin 2 the V supply, this could be a Shottky diode or the Zener diode to ground..

I think it's a Shottky diode. steval-isa118v1_fig.1.jpg
 
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