D747m_1v3 logic board for remote gate

[netgearnetgear]

Good day,
My remote gate stopped working. The company said the main logic board needs replacement. After examining and running a couple of tests, I discovered what looks like a shorted zener diode. Tracing the path on the board it appears to be across a voltage regulator chip (78m05). After reviewing the datasheet for the voltage regulator I thought that it was being used with a zener diode as a voltage boost regulator. However, looking at the layout of the board the "shorted diode" is not connected as in the datasheet. The diode does not have a markings so I am not sure what to replace it with. The 78m05 chip outputs 5v according to the datasheet. I'm assuming that the microprocessor vcc is that. I applied around 1V, 1A after removing the diode and the 78m05 chip to the vcc pin of the d747m_1v3 microprocessor and it drew around 287mA while I eventually raised the voltage to 5v. I believe if the diode in question is used for protection then the circuit may work without it if tested. I have attached some pics hoping that someone can assist me. If I can get a schematic that would be awesome. Thanks for reading my post and I look forward to any feedback.

[R_J]

It might be a 5.6v ~ 6v melf diode, I would replace it, without the diode to short if the voltage goes up over 5v I suspect the cpu would be the next to short, not good

[netgearnetgear]

Your comments are noted. Will do and provide an update asap. Thanks again

[CapLeaker]

It might be a 5.6v ~ 6v melf diode, I would replace it, without the diode to short if the voltage goes up over 5v I suspect the cpu would be the next to short, not good

I think the same. It's just a protection diode for the 5v output of the regulator. This opener should work without the diode for testing.

I suggest to remove that diode and measure the resistance from the 5v rail to gnd.

[netgearnetgear]

Good day, the resistance on the 5v rail is 19 ohms.

[netgearnetgear]

Apologies....it's actually 42 ohms

[stj]

that sounds bad,
42ohms at 5v will be a lot of current

[CapLeaker]

It’s about 119ma of current.

[netgearnetgear]

When I applied 10v (1.5A) at the input (pin1) of the 78m05 regulator chip the current drawn by this part of the circuit is around 287mA at 10v. All other checks on the board tests OK. I will now attach the board and tests it on the remote gate and let you all know how it goes....thanks

[netgearnetgear]

Hello everyone, I wanted to inform you that the board repair was successful. Additionally there were some cracks on the solder joints of the relay pins. The remote gate works fine. Thank you for all your assistance and recommendations...cheers