Help identify a Zener?

[tester272001]

Re: Help identify a Zener?

Sure sounds familiar! I have a large deductable so no help there! the a/c compressor was at end of life so they would not offer much and that would be the largest cost! so not worth it in my case. Oh and the I also replaced a 30 foot length of COAX as that went OPEN. nice huh? I never had so many things go bely up all at once! If I could find a decent screw drive opener, I probabaly would have bought that. But the latest and greatest tech is CHAIN or BELT! wtf? I love my screw drive opener and now its working again. I still have to test those sensors but I think is looking pretty good. Oh and the lightning also went through my attic FAN and put a small puncture through the roof directly under the fan! I was able to patch that with some tar and wood...I hope that never happens again! Within the next 5 or so years I will have to replace the roof due to age so...Overall I feel lucky there was no fire.

[neverthrowaway]

Re: Help identify a Zener?

Hi all,
I'm new to this forum. I've been an electrical engineer in a research lab for over 50 years and am now semi-retired. I have a failed Chamberlain beam detector 14LG372-1A that's bad. I know it's the detector because I have two garage doors with openers and the bad detector doesn't work on either door.
It looks like the diagram Redwire posted of a 14LG372-1B is very close. I think with this information I have a good chance of repairing this thing! I already bought a pair of "universal" units but they are extremely finicky and I can't get them to work reliably, so it's back to repairing the original unit.
As my username suggests I take great pleasure in repairing stuff rather than throwing them out. Two weeks ago I repaired our microwave. Saves a lot of $ but costs time. Another cost (ask my wife) is that we have a lot of old appliances because I keep fixing them instead of throwing them out!
Thanks a lot for your help on this!!!

[tester272001]

Re: Help identify a Zener?

Welcome to the forums Never! sounds like you will have here and also be a great resource!

[redwire]

Re: Help identify a Zener?

Chamberlain Liftmaster garage door sensor 14LG372-1B I have not seen you'd have to post some pictures.

The black IR receiver module runs to 5.5V max (plus a diode drop) so the zener needs to be 6.2V max and 5.6V is the next step down, so 1N4734A 5.6V 1W zener is my guess.

[jopat]

Re: Help identify a Zener?

Hi Red Wire, I am looking at a 14LG372-1B Detector brd. Did you have a print for that? One of the two diodes (D3) was shorted. I replaced it with a IN4003. From what I can see one of the surface mount components on the rear of the board is shorted too. It has the letters 1H on the three leg device. I am not sure what it is. The Transmit sensor seems to be working. My daughter just bought a house with a 1994 Craftsman opener (139.53636SRT). All wires that go to the opener wall button and both door sensors were cut and removed. The door Detector sensor had both connector male legs completely covered in white paint. I cleaned them off and I am trying resurrect the opener. The motor works fine and I can short the first two opener terminals and open / close the door. I was hoping to get the door sensors working on my bench before I go any farther. Thanks for any help you can provide.

[jopat]

Re: Help identify a Zener?

Hello all, I am replying to myself. I just needed to read all of the involved posts to see that Red Wire and others have answered all of my questions on previous pages. I found the exact print I needed. Thank you all for you help.

[jopat]

Re: Help identify a Zener?

14LG472 - I have that schematic.
14LG382 - the schematic you posted but uses lots of parts.
14LG372 - your receiver, I drew a schematic but think you need a zener for D3. Let me know if you get the part numbers for that stuff I can make corrections.

Red Wire, Your schematics were most helpful. I have a question about replacing the NPN BC847 "1H" on a 14LG372-1B Beam Detector Board. DigiKey offers quite a few choices. I could not match up the sizes you listed on your schemo. Could you tell me which DigiKey transistor to get? D3 and The NPN transistor were shorted on my board. I replaced both diodes D1 and D3 with 1N4003. That's what I had lying around. Now to order the little surface mount NPN. Thanks for your help.

[tester272001]

Re: Help identify a Zener?

Jopat, According to Redwire prior post..."The parts are vanilla switching transistors, anything would work"...I just used parts I had on had or on other unused circuit boards

[sam_sam_sam]

Re: Help identify a Zener?

Oh yeah! it destroyed all told: garage sensors, the logic board had 2 fried SOT23 transistors for the relays and one diode across a relay. The Zener 6.2V on the main logic board was shorted. it seems like came in via the sensor and traveled through the A/C mains (flash over lightning?) or it came through the A/C mains and went out the sensors! not sure. I lost Cable modem, router, 2 switches, NAS drive, wireless access point, a small LCD TV and a signal amp in the attic! Oh and I think it did in my 20plus year old A/C compressor (replaced that due to age). When this happended 3 breakers tripped too! I replaced two GFCI recepticles! Whoa! what a list eh?

I had this happen to me twice that lighting struck near my house and twice I had to replace the garage door opener because both times it fried the door sensors and the controller boards on it

And also cable dvd recorder twice also and yard sprinkler controllers

[tester272001]

Re: Help identify a Zener?

I had this happen to me twice that lighting struck near my house and twice I had to replace the garage door opener because both times it fried the door sensors and the controller boards on it

And also cable dvd recorder twice also and yard sprinkler controllers

WOW! They say lighning never strikes the same place twice, I guess that is NOT true!

[alwalker]

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.

[sam_sam_sam]

Re: Help identify a Zener?

I have had this happen to my garage door several times in the past and have never been able to repair them but do not be surprised if the garage door controller is not damaged as well because this has been the pattern that I have seen in the past

Because I have had to replace the controller board and the door sensors as well

[redwire]

Re: Help identify a Zener?

One is the red power on led, the other transmitter infra-red LED is a vanilla 5mm part, around 940-950nm and narrow angle. Like Kingbright WP7113F3BT, or Wurth 15400594F3590.
If you post pics of both sides of the board I can add more info.

If you get low resistance it could be a shorted diode or the LED is shorted.
You can see the IR led light while looking at it with your cell phone camera, it's dim but tells you if it's emitting some.

I would look at replacing a few semiconductors on the board it you have the patience and the opener circuit is not toast. Does the manual switch for lights work? It shouldn't door close without a good sensor signal, for safety purposes.

Lightning strikes seem to come in mains power (to the opener) and then arc over to the nearest ground, like the garage door door rails. So it jumps from the sensors to the rail and can damage either or both ends.
Some garage door openers have MOV kits to add protection, if you live where it's a common occurance. That is a couple of MOV's like MOV-20D271K, each from line-neutral and line-ground at the opener.

[alwalker]

Re: Help identify a Zener?

One is the red power on led, the other transmitter infra-red LED is a vanilla 5mm part, around 940-950nm and narrow angle. Like Kingbright WP7113F3BT, or Wurth 15400594F3590.
If you post pics of both sides of the board I can add more info.

If you get low resistance it could be a shorted diode or the LED is shorted.
You can see the IR led light while looking at it with your cell phone camera, it's dim but tells you if it's emitting some.

I would look at replacing a few semiconductors on the board it you have the patience and the opener circuit is not toast. Does the manual switch for lights work? It shouldn't door close without a good sensor signal, for safety purposes.

Lightning strikes seem to come in mains power (to the opener) and then arc over to the nearest ground, like the garage door door rails. So it jumps from the sensors to the rail and can damage either or both ends.
Some garage door openers have MOV kits to add protection, if you live where it's a common occurance. That is a couple of MOV's like MOV-20D271K, each from line-neutral and line-ground at the opener.

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 be wrong and it could also need to be replaced. I can probably come up with a replacement diode for the power indicator that would work since we know the voltage and current limiting resistors value but I had hoped someone would have known the best replacement or original specs for the power indicator led. I've had many of these sensors fail due to lighting over the years and also had the logic board damaged. I have been able to repair the original logic bd several times over the years but the last time it was hit the damage was too severe and I had to replace it. I have used a surge protector in the past which has not protected anything from being damaged. Last year I installed the Chamberlain surge protector they used to sell that may have some protection at the sensor lines in addition to the power for the logic board. In any case the surge protector did not trip this time but the safety sensor still did get popped.

[stj]

Re: Help identify a Zener?

lightning generates a huge emp,
anything with a long cable run or a coil acts as a receiving antenna

[redwire]

Re: Help identify a Zener?

I'm able to draw this schematic for the 14LG479 Emitter board. Please review for mistakes.
They deleted the surge zener diode that was present on early models

The Power On LED is any vanilla 3mm (T-1) size green that you can find lying around, or off eBay or Ali as penny parts. Sorry I thought it was the IR emitter LED you were after.
Note the board marking "BLK" is +ve voltage, (I think the wire colour is reversed, Blk strip goes to WHT?) it used to run off 6VDC as a current-loop supplied by the opener, giving 5.3V for the entire circuit after the reverse polarity diode D104.
The circuit has two oscillators, one for 150Hz and the other gated 38kHz.
I'd get a new IC and LED and try that, check the IR LED is not shorted as well, it should be OK.

[alwalker]

Re: Help identify a Zener?

I'm able to draw this schematic for the 14LG479 Emitter board. Please review for mistakes.
They deleted the surge zener diode that was present on early models

The Power On LED is any vanilla 3mm (T-1) size green that you can find lying around, or off eBay or Ali as penny parts. Sorry I thought it was the IR emitter LED you were after.
Note the board marking "BLK" is +ve voltage, (I think the wire colour is reversed, Blk strip goes to WHT?) it used to run off 6VDC as a current-loop supplied by the opener, giving 5.3V for the entire circuit after the reverse polarity diode D104.
The circuit has two oscillators, one for 150Hz and the other gated 38kHz.
I'd get a new IC and LED and try that, check the IR LED is not shorted as well, it should be OK.

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.

[redwire]

Re: Help identify a Zener?

What number is on the old part? From the pic, your IC is in a SOIC-8 package.
TI LM2903DR or LM2903-Q1 (automotive rated).
On-Semi LM2903EDR2G, the LM2903M is obsolete
ST LM2903DT or LM2903W (has extra protection diodes) or LM2903YDT, LM2903D seems expensive obsolete.
Diodes Inc. LM2903S or LM2903QS (automotive rated)

This part has been around for many decades since the early 1970's so there are a zillion different ones today.
I would get a LM2903DR as a replacement.

[alwalker]

Re: Help identify a Zener?

What number is on the old part? From the pic, your IC is in a SOIC-8 package.
TI LM2903DR or LM2903-Q1 (automotive rated).
On-Semi LM2903EDR2G, the LM2903M is obsolete
ST LM2903DT or LM2903W (has extra protection diodes) or LM2903YDT, LM2903D seems expensive obsolete.
Diodes Inc. LM2903S or LM2903QS (automotive rated)

This part has been around for many decades since the early 1970's so there are a zillion different ones today.
I would get a LM2903DR as a replacement.

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.

[redwire]

Re: Help identify a Zener?

Yeah any of those IC's will work really. Is yours a Liftmaster?