Continuity across zener diode

[Ashroyer05]

I replaced some components on a power supply. Afterwards the set would still not power on. I checked for shorts and found that there is continuity on both through holes for one zener diode. I pulled the diode to see if it was shorted; however, it was not and tested good in diode mode.

With the diode out I then tested the through holes again and found continuity.

My question:
Has anyone ever seen this before? Is it normal?

[budm]

Re: Continuity across zener diode

That means you still have shorted components on the board, we cannot tell much without pictures and where the Zener is located at.

[Ashroyer05]

Re: Continuity across zener diode

https://www.badcaps.net/forum/showth...667#post415667

Bud, thanks for the reply. I added pics to the link above I'm not sure if they went through or not though.

[Ashroyer05]

Re: Continuity across zener diode

Sorry, try this!

https://www.badcaps.net/forum/showth...669#post415669

[budm]

Re: Continuity across zener diode

You should move this post to TV section, the board looks like Emerson/Funai/Philips TV.
Start a new post in TV section with TV make and model number.

[mmartell]

Re: Continuity across zener diode

It test for short but as bud said it's inparallel with a low ohm resistor so it sets off your meter.

I discovered same thing in the Y Main I was working on - can't say I understand the theory behind it but meh

[LDSisHere]

Re: Continuity across zener diode

It test for short but as bud said it's inparallel with a low ohm resistor so it sets off your meter.

I discovered same thing in the Y Main I was working on - can't say I understand the theory behind it but meh

For a long time I also wonder WTF would you have a resistor in parallel with a diode, until one day BudM posted something that explained it. So hopefully this will help you out.

The diodes in parallel with a resistor are to allow a faster discharge of a device. Usually in power supplies it is there to discharge the gate pin of a FET so it will turn off faster.

[budm]

Re: Continuity across zener diode

In this case it may be used foR the limiting the maximum voltage across the resistor not to exceed the Vz of the Zener, probably part of the Current feedback circuit for the SMPS.

[Ashroyer05]

Re: Continuity across zener diode

I will try to get a new thread started. So in other words the circuit should be testing the way it is? I still do not get any good output voltages from the board. I get one that goes from I think 3.2V for a second down to 0.6V steady. I get no other voltages. I figured maybe a regulation problem but all the transistors test good.

[senz_90]

Re: Continuity across zener diode

For a long time I also wonder WTF would you have a resistor in parallel with a diode, until one day BudM posted something that explained it. So hopefully this will help you out.

The diodes in parallel with a resistor are to allow a faster discharge of a device. Usually in power supplies it is there to discharge the gate pin of a FET so it will turn off faster.

In this case it may be used foR the limiting the maximum voltage across the resistor not to exceed the Vz of the Zener, probably part of the Current feedback circuit for the SMPS.

wow. that is good knowledge. thanks. i don't know that til I am reading this !!

[budm]

Re: Continuity across zener diode

That is why we are here to learn, I learn new stuff here every day.

[budm]

Re: Continuity across zener diode

This is the explanation how the circuits work.

[senz_90]

Re: Continuity across zener diode

Thank you a bunch budm !!