PCB Power Connection Issue

Thread Starter

Surya1234

Joined Apr 23, 2021
40
Hi Readers,


This device was in use for a few weeks by powering it up through only 12V connector. It started shutting off randomly so I powered it up through its AC connector through an Inverter (it converts 12V DC into AC) and the router works just fine.

The observations during the troubleshooting process are captured below. What causes the device to shut off as soon as the dc connector is connected while AC connection is already present, but failing to turn on when only DC connection is made?

Is there any issue on the PCB design between the input DC connector header pin and the router's chip? If so, what could possibly go wrong on the PCB?

1708973489802.png
 

nsaspook

Joined Aug 27, 2009
13,297
Maybe. Too little information, not model information, no pictures, no circuits, no wiring diagrams, no schematics, no ....
 

Tonyr1084

Joined Sep 24, 2015
7,903
First thing comes to mind is a bad solder joint on the DC power jack. If the jack is not well supported, it can behave intermittently. This is in no way authoritative information. As nsaspook said, we don't have enough information to be of serious help. The problem can also be in the power cable. Excessive bending at the plug can break wires inside the insulation and you'll never know it. Except for the shutting off problem.

Before you spend any money on this - fully diagnose the problem. That way you fix what's broke and not everything else.
 

MrSoftware

Joined Oct 29, 2013
2,202
As mentioned above, it could be a number of things. Not knowing anything about it, the first thing I would try to check is if plugging in the DC plug disconnects the AC supply. If yes, then this isolates the DC path as for sure the problem path. From there it could be a cold joint, or maybe the 12V supply whatever it is can't keep up with the current demand and when the voltage drops the device brown out protection resets it. I'm just taking stabs in the dark as there are tons of possibilities, more info is needed.
 

nsaspook

Joined Aug 27, 2009
13,297
Let me add mote information to it. There is a similar model which works just fine with the same DC power cable.
Ok, so it's not the DC power cable.

Please at least give us the exact model that's having the issue with power and any CLEAR pictures of the PCB near the power section, power socket/plugs if you can. The more actual information on the actual device the better.
 

Thread Starter

Surya1234

Joined Apr 23, 2021
40
This device is shown below. I don't have its internal details such as PCB schematic.

When power is fed to the connection (pointed by green arrow) (12V--> Inverter-->Brick-->finally DC input to the circular connection: The box stays on and works just fine.

When power is fed to the connection (pointed by the green arrow) (12V directly from battery through a fuse); the box sees intermittent connection issue. But the other box box doesn't see any intermittent connectivity issues.

Another interesting observation:

step 1- non-green connection was made the faulty box stayed OFF
step 2- non-green connection was removed and then the green connection was made. The box was turned on and stayed on.
step 3- non-green connection was made while the box was ON with the other connection, the box got turned off. If the non-green connection is not able to power the device, then why is it causing the box to shut off while the other connection is there?


1708986328675.png
 

nsaspook

Joined Aug 27, 2009
13,297
https://download.peplink.com/manual/pepwave_max_firmware_manual-fw7.pdf
1708994150859.png
These enterprise type routers have redundant failover power (and likely wireless circuit) switching with the terminal block as one power source. If the circuit senses the correct voltage on the terminals of the terminal block it switches the main circuit power to that source. If that power source is missing then it uses the secondary redundant source(s) if they have voltage. The source sense part seems to be working but the power switcher relay/transistor/etc.. part of the circuit seems to have a open or bad connection from the DC power block somewhere. IMO you need to send it in for professional repair or replacement if this is being used for business or industry.
 

MisterBill2

Joined Jan 23, 2018
18,538
Let me add mote information to it. There is a similar model which works just fine with the same DC power cable.
What I have seen is that there develops a broken solder connection between the power connector solder posts and the printed circuit board. What is to blame is either poor soldering or a poor mechanical design that provides no support for the power connector other than the solder connection. For some routers the repair may be a simple re-soldering of the power connector. Given that the unit still functions with the mains supply connection, that points toward the failed connection being with the center pin.

I have seen the same failure resulting in the loss of a name-brand (DELL) laptop computer, where the cost of disassembly to resolder the connector exceeded the replacement cost for the purchase of a replacement computer.
 
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