Hi everyone - I was taking apart my 9090 heat sink to replace two blown output 2SC1116A transistors. I am a resourceful newbie when it comes to electronics and I manage most of the 9090 bring back to life stuff based on the forums, the service manual, some basic tools and meters I got since high school. Occasionally, I run into mysteries such as this:
What is the white stuff smeared all over the heat sink and on the transistors bottom. My guess would be this is some heat resistant insulator paste but I have no idea what it's called, where to get it and how to apply it? It seems to me it should not get on the transistors legs - but it did. Can anyone hand me a pointer? Thanks.
If I understand you, that seems like thermal paste. Thermal paste is designed to compensate for machined imperfections in the heat sink that results in a less-then-flat surface resulting in less contact. Thermal paste just maximized the effectiveness of the heat sink.
As long as you get new paste that is NON-CONDUCTIVE then you will be fine, it won't matter that it got on the legs, unless you haven't soldered them in yet, in which case it will probably prevent the solder from sticking. Radio shack has thermal paste, but again, you want non electrically conductive paste. AKA Thermal paste, aka thermal grease, heatsink paste, etc...