Daewoo DV-K813 VCR video loses time at power cuts (battery)

[pdallas]

Hi, I am writing this to help anyone who might have had the same problem as me. I bought a great Daewoo VCR somewhere around 2000, called a VQ867S.
Every time there was a power cut, or I unplugged it from the mains, it lost the time and all programmed start/stop times. What was worst is that it would enter into the menu and display "RF36", awaiting setup using the remote control. This was very annoying, but I lived with it for 10 years.
Last month, I finally got around to fixing it. I discovered its chassis is actually a Daewoo DV-K813, for which I found a manual on the internet, thanks to Todd Terry.

The board was supposed to have an 0.1F 5.5V ultracapacitor at C524, but it was not fitted! So I got bought one and fitted it, but that only kept the time and settings for a few seconds. I discovered the circuits draw about 3mA from the battery when the mains is unplugged, so it is no surprise it doesn't last long. This is why Daewoo didn't fit the ultracapacitor!

Here is a solution which worked fine: I got four AA-size (1.2V, 600mAh) NiCd batteries from one of my son's old toys, and connected them in series, and then to the PCB where C524 is supposed to go, through a 15 Ohm, 5 Watt resistor. The resistor is absolutely necessary because, without it, if the batteries happen to be empty, you are essentially putting a dead short across the VCR's 5V power supply; I am not sure it will like this.

Having done this, and having let the VCR plugged in for a few days to make sure the batteries charge nicely, it has been working like a charm, and keeps the time and settings even when mains power is disconnected for a day. I hope this also works for you!

DV-K813S / K413S / K213S Series
DV-K823S / K423S / K223S Series
DV-K843S / K443S / K243S Series
DV-K863S / K463S / K263S Series
DV-K873S / K473S / K273S Series
DV-K893S / K493S / K293S Series
DV-K9A3S / K4A3S Series