Re: Help identify a Zener?
I would think the mains ground. I wish I had an easy way to install an extra ground rod near the basement opener. That one is furthest from the electric entrance panel. BTW--I did check the condition of the ground rod and wiring at the meter. No problem there. I do suspect since the opener I have had the most lightning problems with is the furthest from my electric panel and that ground rod another ground rod directly attached to the rails might do the trick. I wish I could do it easily in the basement without tearing up the concrete floor...
alwalker
Member
Last Activity: 07-05-2023, 02:27 PM
Joined: 06-04-2023
Location: Stokedale, NC
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Re: Help identify a Zener?
I have two Liftmaster garage door openers and they both now have the 990LM surge protectors wired into them. I was a little curious about the protection going to the safety sensor and opener switch so just to see the answer I would get I sent an email to Chamberlain/Liftmaster asking (1) why the 990LM was discontinued, (2) if they had a schematic of the 990LM itself available and (3) if it protected the logic board or if it actually protects the safety sensors. Here is the response I got:
[I]Thank you for contacting Chamberlain Group Technical...Last edited by alwalker; 07-03-2023, 01:23 PM.Leave a comment:
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Re: Help identify a Zener?
I wonder if anyone makes a residential opener that uses wireless safety sensors and wireless door opener switch. That would pretty much eliminate almost all of my lightning strike issues. I wouldn't mind changing a battery or two once a year--people do that already with smoke detectors in their house.Leave a comment:
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Re: Help identify a Zener?
I believe it has to do with the rails and sensor wiring. Almost every time I have had damage to the sensors you can see a scorched area on the pc board that leads back to the screw which mounts the sensor board and sensor to the rail. You can see it in the picture I uploaded. I will check the electric panel ground but I don't think I'll find a problem there....Leave a comment:
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Re: Help identify a Zener?
Thanks for the drawing. I scrawled pretty much the same thing out for myself already but yours looks much better. I didn't want to post the one I did because it looked amateurish. Perhaps I phrased it in a misleading way but I did not have a 990LM with green light go out. The one I have still indicated it was protecting the AC line. I was just referring to the fact that the emitter sensor board had obviously been damaged by lightning and after looking at the lightning suppressor circuit it appeared to me that the mov m4 could have been damaged...Leave a comment:
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Re: Help identify a Zener?
I took one apart that I just received--only three screws and comes apart easily. The 990LM does not use MOV's that have a built in fuse. The main board has mov's m1 and m2 as GNR20D431K and m3 is GNR14D431K. It does sandwich a thermal fuse between m1 and m2 and tape it all with what I suppose is a tape that will not go up in flames? The board that goes to the opener sensors and control uses a 14D201K. Since failure of that MOV would not result in the indicator led not lighting up I think I will take that one down and look at it to see if...Leave a comment:
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Re: Help identify a Zener?
I'll have to see if the 990LM comes apart in a way that lets me put it back together again. Almost everything made nowadays in China "snaps" together and I would hate to break a new working surge protector right off the bat. That might be the easiest way though to get the right values for all of the components--definitely harder to do when things get burned and blown up. If I take one apart I'll post photos. I should be getting it delivered later this week....Leave a comment:
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Re: Help identify a Zener?
Thanks for the info. I can still get new 990LM units on Ebay. I have 2 doors with Liftmaster openers and installed one last year on the one that always gets damaged every year or so. I believe I will purchase another one today for the other door. In the event one of them does absorb the brunt of our next lightning strike I will definitely take it apart just to see what the circuit looks like....Leave a comment:
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Re: Help identify a Zener?
I wonder if that's what is inside the Liftmaster/Chamberlain surge protector they sold for use with the openers? Do you perhaps have a schematic of that (990LM or CLSS1)?...Leave a comment:
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Re: Help identify a Zener?
The LM2903D and the power led were all that I needed. Everything works. I will set aside the sensor kit that I purchased and use it if the next lightning strike does more damage than can easily be repaired....Leave a comment:
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Re: Help identify a Zener?
Yes. If you ever want to attract lightning owning one of their openers will do it....Leave a comment:
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Re: Help identify a Zener?
The original was LM2903M. I already ordered some LM2903D ic's and the led from eBay. I think any of them will work that are 903 based although the LM2903DR would have been a better choice. I'll let you know how it goes....Leave a comment:
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Re: Help identify a Zener?
LM2903D sub ok for the original LM2903M? Yes the IR LED is not shorted. I'm hoping just the power led and the IC will do for this board. Thanks....Leave a comment:
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Re: Help identify a Zener?
Not that the color matters but this is an older style 1995 sensor and the power indicator led on both the emitter and receiver were both green. I have already determined the emitter board is the only problem by installing a replacement board. The receiver and logic boards are fine. I'm just trying to see if I can repair the old emitter board. The power led reads 15 ohms across it. I can supply power to the board and the ir led will light up but since the receiver does not recognize it I am assuming the comparator ic has failed. I could...Leave a comment:
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Re: Help identify a Zener?
I've got the same emitter board 14LG479-2C that is not working. I believe LM2903 is my problem but I found something odd when checking the components on the board. The indicator led, D105 reads 15 ohms and is not lighting. Does anyone know what to replace that with? That is of course not what is causing my IR pulse problem but it does seem odd that this should be bad. Again though--the damage is due to lightning. You can see a slight scorch mark on the board near where the bolt would pass through the board to mount the sensor to the door rail.Leave a comment:
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