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Old 09-17-2020, 09:57 PM   #1
tester272001
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Default Help identify a Zener?

I have been looking around for a xref to see what this zener might be. I think it might be a 5V zener but the markings are strange to me. Please see pic showing all sides. I cannot tell if the marking is Z05280029 or Z052B0029 or how to read this. Any help is appreciated.
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Old 09-17-2020, 11:28 PM   #2
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Default Re: Help identify a Zener?

That is not 'Z', the the 'N' logo of National Semiconductor.
https://en.wikipedia.org/wiki/National_Semiconductor

You can find out if it is 5V Zener or not by connecting 470 Ohms resistor in series with the Zener in question then connected them to 9V battery in reverse bias then just use Volt meter to check the Voltage on the Zener in question.
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Old 09-18-2020, 07:11 AM   #3
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Default Re: Help identify a Zener?

Bud, thanks for the feedback! N makes sense! I've seen the test procedure before and I can try that. But I suspect this device as bad. So measuring the voltage might not give me the voltage it is SUPPOSE to be but the defective one. That is why I wanted to lookup the device. Maybe now that I know is National Semiconductor I can look it up! THANKS!
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Old 09-18-2020, 09:02 AM   #4
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Default Re: Help identify a Zener?

seems to be a custom part number, what/where did it come out of?
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Old 09-18-2020, 11:33 AM   #5
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Default Re: Help identify a Zener?

this is from an Emitter board of a garage door safety sensor. The IR led seems a little dim. It is proprietary by Liftmaster. No exact schematic around and of course no parts list. I cannot seem to cross reference this part. Even knowing it is National it seems TI does not provide any backward lookup for diodes, mainly I see other active components. If you have any TIPS I all all ears! thanks!
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Old 09-18-2020, 11:43 AM   #6
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Default Re: Help identify a Zener?

probably just the led failing
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Old 09-18-2020, 12:15 PM   #7
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Default Re: Help identify a Zener?

Agreed. Is likely the LED. I see there are 2 primary LIGHT frequencies for IR leds (unless I can find a marking on teh IR LED) so I need to either try both wavelengths or see which one the IR receiver uses. it is a TPMS5380 receiver (38khz). I did have to replace a 6.2V zener on the supply so I wanted to check this one for proper voltage.
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Old 09-18-2020, 01:29 PM   #8
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Default Re: Help identify a Zener?

Post pics of the board. I did schematics for a couple generations of Liftmaster/Chamberlain/Sears garage door sensors. It's a 150Hz pulse train of 38kHz bursts from an LM2903.
It's usually the IR receiver module that fails in cold weather.
Original is TSOP1238 and I've heard a TSOP33338 works for a replacement.
D106 is a 1N4148.

Liftmaster 14LG472-2B, 14LG472-1B, 14LG372-1B; did not finish a 14SR472-1B schematic.
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Old 09-18-2020, 02:38 PM   #9
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Default Re: Help identify a Zener?

here is the front and back of the EMITTER
14LG47S-2C
I put a temporary DIODE in ther,e the original was shorted. This was flashover lightning/strike.
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File Type: jpg emitter_font.jpg (123.7 KB, 47 views)
File Type: jpg emitter1.jpg (72.5 KB, 35 views)
File Type: jpg emitter_back.jpg (151.1 KB, 32 views)

Last edited by tester272001; 09-18-2020 at 03:45 PM..
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Old 09-18-2020, 03:48 PM   #10
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Default Re: Help identify a Zener?

the only schematic I found was darn close but older for sure. Doe snot identify actual part VALUES for some components.
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Old 09-18-2020, 07:32 PM   #11
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Default Re: Help identify a Zener?

Thank you so much for this schematic, this will go a long way for me to figure out my garage door even if it's not the same. Looks like it too has a bad cap in these units. But anyway the schematic exposes quite a bit of information for me.

But it looks like D104 - if that's the unit that's having problem - appears to be a generic diode and you can replace it with anything. Looks like you have a 1N4001 or something like that, it should be fine... is it working?

Agreed that the LED itself may be damaged now, quite possibly as a result for D104 shorting, so watch for that.

Also it seems that there are no zeners on the board. D107 is the only zener in the schematic, and it looks like the PCB was designed for it, but not silkscreened on the front. It looks like there's a spot for it where "D104" is printed but there's no marking for the true D107. If you want to put in a 6V zener you can, and it might save you from it zapping again and having to fix it again in the future.

Last edited by eccerr0r; 09-18-2020 at 07:38 PM..
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Old 09-18-2020, 08:34 PM   #12
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Default Re: Help identify a Zener?

Here is my schematic for older very similar 14LG472, yours is 14LG479. Same basic circuit as the other. The diode is not a zener but is a 1N4002 in series with power to the board.
Very hard to kill a 1N4002 there, it must have been a -ve spike that hopefully found no path to arc.
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Old 09-18-2020, 11:05 PM   #13
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Default Re: Help identify a Zener?

Ecc, Glad to help ! And Red thanks for the schematic. When I saw the red and black casing on the diode it definitely reminded me of a Zener. The silkscreen does not show it as one! When I did a diode test is shows good. So next I will hunt down my IR LED and give it a try!
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Old 09-19-2020, 01:27 AM   #14
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Default Re: Help identify a Zener?

Quote:
Originally Posted by tester272001 View Post
the only schematic I found was darn close but older for sure. Doe snot identify actual part VALUES for some components.
but it shows the zener voltages.
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Old 09-19-2020, 08:58 AM   #15
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Default Re: Help identify a Zener?

Yes the D106 in the schematic I posted has 2 resistors with +5.3V off them and 4.3K Ohm resistor feeds D106. It also does not depict as ZENER (as it does for D107) - so is my diode a 1n4001 or a 5V zener ? Even the schematic Red posted does not show as Zener.
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Old 09-19-2020, 01:32 PM   #16
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Default Re: Help identify a Zener?

In your PCB, there are no zener diodes at all. All are regular diodes. If any of them were actually zeners, the behavior would be weird.

However in your PCB, physically where the label "D104" stands on top of (not the actual component that it's currently pointing to), you can see two holes to either side, where there's no component there. Those two holes probably used to be for D107 but is not labeled as such anymore. That position used to be a zener diode - 6 volts according to the schematic. You can put a 6 or 6.2V zener diode there if you wish, but make sure you get the polarity right.
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Old 09-19-2020, 01:40 PM   #17
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Default Re: Help identify a Zener?

The emitter does not care so much about it's operating voltage, the IC is good to 36V. The receiver module is a 5V part though so a zener there would be needed.

Since these (emitter, detector, light switch) are all on the same two-wire (sorta constant current) bus, I have to wonder if the receiver survived the lightning surge.
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Old 09-19-2020, 10:21 PM   #18
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Default Re: Help identify a Zener?

Until I get the emitter pulsing the 38K frequency I won't know for certain. I suspect the receiver may have gotten zapped as well. I did not detect any pulsing on the U1 device when I put the output on a scope. I thought that maybe the emitter was not strong enough to make the receiver pulse.
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Old 09-19-2020, 11:14 PM   #19
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Default Re: Help identify a Zener?

Try a TV remote pointed at the receiver, sometimes the pulse pattern will fool them for a bit.
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Old 09-20-2020, 08:22 PM   #20
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Smile Re: Help identify a Zener?

Quote:
Originally Posted by eccerr0r View Post
In your PCB, there are no zener diodes at all. All are regular diodes. If any of them were actually zeners, the behavior would be weird.

However in your PCB, physically where the label "D104" stands on top of (not the actual component that it's currently pointing to), you can see two holes to either side, where there's no component there. Those two holes probably used to be for D107 but is not labeled as such anymore. That position used to be a zener diode - 6 volts according to the schematic. You can put a 6 or 6.2V zener diode there if you wish, but make sure you get the polarity right.
The D107 in later models was MOVED to the Main board and is called D10. it is a 6.2V Zener. That was blown on the logic board. Replaced that and a few SOT23 transistors and that board is FINE
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