strange diode identification - Page 1
Forum section: electronics / repair

author: electricenthusiast
author_rank: Contributor
timestamp: January 23, 2023, 02:28:32 am
content: This is a failed/ shorted zener diodeI got this from a failed sony dvd (sony_dvp-ns57p) smps. this smps turns on but it is giving out voltage higher than it should .So I removed the optocoupler, checked it, and resoldered it to the board. And now, when I switched on the powersupply( without connecting to the mainboard) it started to cry. So I let the powersupply to run untill the failed component to get hot. And it was this zener diode which look like a resistor but only 2 color bands. What is the value of this zener diode

author: fzabkar
author_rank: Super Contributor
timestamp: January 23, 2023, 02:38:17 am
content: Service manuals:https://elektrotanya.com/showresult?what=dvp-ns57p&kategoria=All&kat2=All

author: electricenthusiast
author_rank: Contributor
timestamp: January 23, 2023, 11:49:13 am
content: I already have this service manual. It also has the zener listed in it , but no values are givenCould it be a 46 or 47v zener diode?Is there any way to find the value using the color ring . I think it is 47v but still not sure

author: Swake
author_rank: Frequent Contributor
timestamp: January 23, 2023, 04:40:25 pm
content: What zener is it in the schematic? There are several.Why do you think it is 46V (or 47V)?

author: electricenthusiast
author_rank: Contributor
timestamp: January 23, 2023, 05:08:27 pm
content: by the color rings on it Yellow and blue4 6 v -> 46v But there is no 46v zener, so it might be 47v ? not sure about that

author: fzabkar
author_rank: Super Contributor
timestamp: January 23, 2023, 05:29:54 pm
content: "What zener is it in the schematic? There are several."

author: electricenthusiast
author_rank: Contributor
timestamp: January 24, 2023, 02:31:54 am
content: this one

author: Swainster
author_rank: Frequent Contributor
timestamp: January 24, 2023, 03:25:05 am
content: I'll have a guess and say its a Panasonic MAZ2470. However its function looks like over voltage protection, so if your output is too high and the diode is getting hot then it is just doing its job I.e. it's a symptom and not a cause.

author: gamalot
author_rank: Super Contributor
timestamp: January 24, 2023, 12:28:16 pm
content: Quote from: Swainster on January 24, 2023, 03:25:05 amMAZ2470 looks like the most reasonable guess to me. The blue band might just be caused by digital cameras, sometimes they don't capture purple very well.

author: electricenthusiast
author_rank: Contributor
timestamp: January 24, 2023, 12:53:35 pm
content: yes you are right it was purple . let me try replacing it with that

author: electricenthusiast
author_rank: Contributor
timestamp: January 24, 2023, 03:38:16 pm
content: Panasonic MAZ2470 zener is no longer available. Can i use 1N4756 zener instead ?

author: wraper
author_rank: Unknown
timestamp: January 24, 2023, 03:42:37 pm
content: Quote from: Swainster on January 24, 2023, 03:25:05 amYes, with elevated output voltage defect replacing it won't fix anything.

author: electricenthusiast
author_rank: Contributor
timestamp: January 24, 2023, 05:39:45 pm
content: But that zener was already shoted/failed

author: wraper
author_rank: Unknown
timestamp: January 24, 2023, 06:04:29 pm
content: But do you get a normal voltage without it installed? If you don't fix high voltage issue, you will just burn another zener diode when powering on the PSU.

author: fzabkar
author_rank: Super Contributor
timestamp: January 24, 2023, 07:05:19 pm
content: ISTM that the zener has +11V on the cathode and -10V on the anode. That's 21V. If a 47V zener is shorting due to a fault, then the overvoltage must be serious.

author: electricenthusiast
author_rank: Contributor
timestamp: January 25, 2023, 02:17:34 am
content: I dont know the actual value of the zener, but that zener was already failed/shorted. But how did you found that the zener has +11V on the cathode and -10V on the anode. That's 21V ?

author: fzabkar
author_rank: Super Contributor
timestamp: January 25, 2023, 03:01:00 am
content: Quote from: electricenthusiast on January 25, 2023, 02:17:34 amFollow each end of the zener to CN201. There you will see EVER-10V and EVER+11V. The voltage difference is 21V.

author: electricenthusiast
author_rank: Contributor
timestamp: January 25, 2023, 12:12:21 pm
content: So should i replace it with a 21v zener? there is no 21v zener .So should i use 22v or 20v zener ?

author: electricenthusiast
author_rank: Contributor
timestamp: January 25, 2023, 01:40:12 pm
content: which should i use ?

author: fzabkar
author_rank: Super Contributor
timestamp: January 25, 2023, 03:56:13 pm
content: No, a 21V zener would be on the borderline. There must be a reason that the original zener was 47V, but I can't understand what that could be. I would wait until you repair the circuit, and then examine the voltage between the zener's pads.

author: electricenthusiast
author_rank: Contributor
timestamp: January 25, 2023, 05:31:04 pm
content: Quote from: fzabkar on January 25, 2023, 03:56:13 pmI'm not at all sure whether that zener is 47v. I'm just assuming it to be 47v based on the color rings on it, with the help of that chart

author: electricenthusiast
author_rank: Contributor
timestamp: January 26, 2023, 05:17:43 pm
content: Quote from: electricenthusiast on January 25, 2023, 05:31:04 pm

author: electricenthusiast
author_rank: Contributor
timestamp: January 27, 2023, 02:23:43 am
content: After repairing the smps, when i plugged it to the dvd, after pressing the power switch, the voltage from smps just dropped like 11v ever to 7.11v , 8.8v to 4.9v and so on. Is there any problem with the primary high voltage part ?