Statement of Empiricism
I have used this heating pad for several years now (I wrote these instructions in December 2007, it's now February 2011). I have had exactly ZERO issues with it - it works perfectly and the hedgehog is fat and happy. YOUR MILEAGE MAY VARY! PLEASE USE EXTREME CAUTION IF YOU FOLLOW THESE STEPS. If you do this, closely observe the pad for at least a few days to make sure it's not overheating or catching on fire. See the obnoxious red text below:
USE CAUTION! TRY AT YOUR OWN RISK!
YOU WILL VOID YOUR WARRANTY!
So, I got this heating pad at the store a while back to use as a hedgehog heating pad. I found out that the 2-hour auto-off timer was hardcoded into the circuit, and they didnt even bother to put a switch on the casing to disable it. Typical overprotection of the consumer - this wouldnt exist if our country was a bit less litigious.
African hedgehogs need at least 72F to be happy, so a heating pad under the cage is recommended. I mean, how could you say no to his face?
So, to disable it, I decided to take it apart and find the culprit like this guy did. Its too bad that for some reason they decided to make it even harder to change this feature.
Step 1: Surveying the Situation
07.28, and I have no idea what that means.
Step 2: Doing the Modification
So, the deal is that after a lot of trial and error, I finally found which single pin on the IC you have to cut. I’ve circled the IC in the picture below.
It’s PIN #2!
OK, it actually isn’t #2 on the schematic, but in the picture it makes sense. Just take a soldering iron and a sharp pointy object (I used a thumbtack), melt the solder, and pry the pin from the board. Be careful not to touch pin #1 - if you disconnect it, it will turn off every 5 minutes! Then, put the entire thing back together and celebrate!
I used the datasheet for the IC chip to figure out what pins to screw with. I can’t find the number of the chip right now without tearing the whole thing apart again. Basically, the chip is just a counter, and you cut one of the pins that makes it increment. So simple.
Now I have a happy hedgehog. He’ll never be cold again.
Step 4: Also, the Sunbeam Model 836
Nick V has modified his Sunbeam Model 836. For those interested, here’s his description of the mod:
The chip is a CD4060 (14 stage ripple counter) on mine. They use it as count up timer to turn the ac to the heater coils off after two hours. I wired in a 10k resistor pullup to Vdd to pin 12 (master reset). This disables the counter function, and voila, no auto off!
I went ahead and found the datasheet for all you kids looking to try this. I extracted the one piece of information you probably need, which is in the attached picture.
Nice job, Nick! Hats off to you!