Then it's not a true Sears unit as the title screens will show the "Mattel Electronic presents". Better to open it and reseat the main chips. Start there.
If the shell is in really nice shape, it might be worth keeping. The Sears units are hard to find without yellowing, deep scratches in the paint...etc. depending on what you paid. If go for another beatup, but working Inty and swap the chips to a know good motherboard so you know your Sears set works. If they do, swap boards
With these old units, you need a spare set to test with and pull parts from. It's just to be expected
Okay, so, I decided to keep it and hope I could fix it because it had a great picture for the RF. The composite was good except for the pink water. It also had the only decent working reset button of the 3 intys I have and came with two good working controllers. I'm hoping maybe the composite can be improved as well. I have heard you can use an IC to clean up the power rather than going straight from the 5V pin.
Anyhow, I spent about eight hours working on it the last three days. I cleaned the switches, RF port and cart port with detoxit and I moved the cart port teeth out a bit. I reseated all the socketed chips. Again, worked good for 7-10 minutes and then graphics corruption for a minute and then only pink or black screen. I used another spare Intellivision 1 that has lost its reset board dome, somehow, and tried swapping power board and transformer from the Sears to the Intellivision and the Intellivision worked good. Then I put the sears back together and tried the Intellivision logic board in the Sears and it worked good. So that narrowed it down to the sears logic board. I switched all the socketed ICs on the Intellivision board to the Sears board. Things got a little confused here because I later found a bent pin on one of the ICs I'd reseated that I missed because it was under and between two of the winged heat sinks (what crappy heat sinks) and also with all my experimentation, the ribbon cable started getting to where it was not connecting well.
The Intellivision with all the corresponding nine-ish Sears chips moved to it worked good. For the Sears console, I ended up having to solder wires to the 5 pin contacts and trying to plug the wires into the power board connector, which sucked because the pin contacts are about a mm apart and I suck at precision soldering, so it took me about 3-4 times to get it right. After this I tried it and it ran for 20 min before graphic corruption and pink screen. I tried to adjust the wires poked into the connectors and the last time it ran for a half hour with no problems noticed, except I had to re-insert the cart once. I still need a better solution for the ribbon cable on the Sears to see if it will continue to work better.
I noticed one of the ICs with the heat sink on it (the one on the far right without another one above it) and the two transistors above it on the board all get very hot.
Ultimately, I am hoping it was a ribbon cable going bad and the heat was expanding it to cause partial contact loss after a few minutes. I'll be able to tell better once I find a good ribbon cable replacement and install it. Otherwise, I will need to look into the three items that are getting too hot. I have to check out voltages on the power and transistors also, but that seems pointless if the ribbon connector hasn't been replaced.
Also, I don't care much for the on-switch on the Sears model, seems like it doesn't give space to quite fully switch to the on position like I would like. Another 2mm of open space to the right of the switch would have been nice.
In another subject, the intellivision 1 used above seems to intermittently have problems with the controllers working, even though I have added known working controllers to it.
P.S., I am going to try these for a ribbon cable replacement. May be way too long and have to modify.