Troubleshooting My Cameras

*OFF-TOPIC*
I do have a hotspot installation display. However, I have just ordered new batteries for it. I bought it a while ago from Speco (before I moved on) and since I overpaid for it, I have kept it alive ever since. The internal battery was too large for it and would automatically press the front buttons. I took the battery out of it, took the button overlay out of it, and attached a rechargeable lithium-ion battery to the back of it. I lost the charger for it and couldn't find the same replacement without buying it with the battery. It will be back online soon and will not need an extension cord to work.
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I first tested the power supply, which was reading about 27VAC. I recall this to be the same voltage originally measured at the initial install. The cameras have worked for 4 years.

I then tested the video cables to make sure they were in working order.

I tested the fuses and everything checked out. I also swapped power leads to different terminals and the working cameras functioned on every power supply output.

I measured the current on the working cameras and the non-functioning cameras. This was a good sign of problems. It was tested when the store was well lit so IRs would not be on. The working camera's current was measured at 122mA and the non working cameras measured at about 13-20mA. In a no-load condition, there was no current draw. The meter I used was a Fluke 115.

NOTE: I also took down each non-working camera and tested locally at the recorder/power supply location to eliminate the cable altogether.

The new replacement camera would power up with a 12VDC 1A power adapter. The working and non-working original cameras would not power on with the same power adapter. They were indeed dual voltage cameras so I though this was strange.

All the replacement cameras worked fine without issue when replaced on the same original cable.

*OFF-TOPIC*
When focusing cameras, I generally use my laptop on a ladder via WiFi on the LAN and view the original resolution. I also use the welding glass over the lens to engage the IR cut filter and open the iris. I have found this works fairly well. I go back and forth to achieve the optimum focus.
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What I am really looking for is possibly what could have gone wrong from an electronics point of view inside the camera itself. When measuring the video output with the meter, there was no voltage output like there is with a working camera. It just blows my mind that it went from one non-functioning camera to five. Now I can say the front door camera did need to be power cycled because the camera went to an all-white state. When reset, it went back to normal and hasn't had any other problems. This was about a month ago when I was there to take care of the POS system.