# Identifying an SMD diode and an SMD Zener diode

I'm trying to repair an DG96-00216C inverter board from a Samsung appliance. My knowledge in electrical engineering is pretty limited.

The board is plugged in to 240VAC with a 25A slow fuse. This board sends power for the right back and right front induction coils.

There's a simmer & boost mode option for each. It's the boost mode that has ended the life of the two IGBTs of the bigger cooking zone.

Here is the list of bad components I've found so far:

• 2 IGBT (IXGR40N60C2D1 600V 56A 170W)
• Rectifier bridge (D25XB60 600V 25A)
• 6 10Ω SMD resistor
• some SMD diode (marking W1)
• some SMD zener diode (marking ZB)

Here is my list of replacement parts:

• 2 IGBT (‎IXGR72N60C3D1‎ 600V 75A 200W)
• Rectifier bridge (GBJ2510-BP‎ 1kV 25A)
• 6 10Ω (1206 casing) 1W SMD resistor

As for my diodes, I have no clue. I have a DMM but I don't know any way to measure them.

I can't really measure the voltage on the board since it is not working.

I've checked all capacitors and they all seem to be good. I've checked the regulator transistors and they are good, too. Continuity test was performed on all transformers.

Sorry for the poor diagram. I just learned what an IBGT and a bridge rectifier was this week. All symbols might be wrong (capacitor types & diode types.)

What might the diodes marked W1 and ZB be?

Update - 9th November

I bought a 0-30V variable power supply and I did some test. With two DMM (one setted for amp measurement and the other for voltage measurement) and my PSU I found the zener voltage of my zener. $$\V_z = 19 \text{v}\$$. $$\V_f = 0.7 \text{v}\$$.

I bought somes Rohm KDZTR18B (Rohm KDZ18B is 18V).

As for my diode, $$\V_f = 0.6 \text{v}\$$, but the reverse voltage is still unknow. By connecting my 32V PSU and two other 12V PSU I was able to reach a 56V without even reaching his breakdown voltage (protected with a big resistor, my diode had only 50µA through it). So I'm roughly guessing $$\V_r ≥ 75 \text{v}\$$. I decided to buy somes 100V 2A schottky RB068MM100 and some 100V 300mA 1N4148WQ-7-F. I don't which one I will use yet. They are both fast recovery diode. I've selected higher voltage and amp just to be sure they do not blew up.

• Your zeners might be NXP PDZ-B series. ZB marking would make them 6.8V Commented Nov 2, 2020 at 17:17
• The diode is probably a jelly-bean 1N4148 or similar. Commented Nov 2, 2020 at 17:18
• Possibly, found a 1N4148 with W1 marking biakom.com/pdf/1n4148w_dio.pdf. Either that or it's some schottky. All it does is bypass the resistor for fast turn-off. The zeners might also be Rohm KDZ18B. Commented Nov 2, 2020 at 17:22
• I'm working on the same problem with the same board (KO = 2 x IGBT -GP4068D ;2 x 10R0 ; zener diodes ; diodes). On my board : D109/209 diodes seems to be LL4148 - ZD201 is a Glass SMD marked [RED yellow green blue] but I cannot identify clearly value even with color code => probably ZD= 19V like you? Did you finally make it work again? Can you share final value used? Zener Diode D209/D109 Commented Apr 5, 2021 at 23:33
• I recommend against people trying these repairs, especially if they don't have experience working with electronics! I want to share that I've had at least 8 clients send in their boards to us for repair after trying these "instructions", and all of them were no longer repairable (except 1 where I had to charge extra). (not all jobs are DIY) This is often ending up costing people huge amounts of money, with ranges ending up in landfills, and also loss of income for us in trying to professionally repair the boards. [Edited by a moderator.] Commented Sep 4, 2022 at 12:52