Constat current source mosfet installation question

markmaloof · « **on:** 4 Nov 2005, 06:28 pm »

For the Cornet classic board, does the mosfet for the CCS upgrade have a "direction", or can it be soldered into the three pin socket facing either way? The mosfet has a silver ring on one side, identification writing on the other side. I noticed that the diodes had direction (grey bar at end) when I installed them, so I followed the icon on the board. Did not know if the transistor does as well or not.

Then when I'm done, I pull the cute 'lil heatsink I ordered along with the mosfet from Mouser over it, right? (in other words, cover the whole mosfet with the heatsink, rather than affix it to one side of the mosfet. The over fits over it nice, and it looks like from the CCS photo that it just pulls over.)

GRD · « **Reply #1 on:** 5 Nov 2005, 12:21 am »

Yes, they have a direction. So make sure you orient correctly.

hagtech · « **Reply #2 on:** 5 Nov 2005, 01:03 am »

Look on page 8 of manual. Photo shows current sink components. I used the exposed metal part of transistor package as the wide that touches heat sink. These parts have odd pinouts.

jh

markmaloof · « **Reply #3 on:** 5 Nov 2005, 03:40 am »

So correct me if I'm wrong, but it looks like in the photo that the exposed metal side of the transistor is is facing towards R1, R11, C6, etc, with the heatsink applied on that side, no?

Also, the heatsink was one I ordered as per a CCS threat here, mouser part # 532-577500B00. It looks like it was made to pull over the mosfet (not a finned heatsink, a smooth odd shaped one with a hollow center.) Would this be bad for the transistor? Would I be better just affixing it to the metal with some of this silicone glue I picked up at Ratshack (also recomended by a post here.)

hagtech · « **Reply #4 on:** 6 Nov 2005, 07:24 am »

Aha, forgot I oriented transistors differently per channel - on Classis Cornet board. Metal side of transistor faces R6L and R1R.

Style of heatsink also changed, but the ones you have will work just as well.

jh

markmaloof · « **Reply #5 on:** 6 Nov 2005, 07:32 am »

Jim, thanks for your reply in regards to orientation of the transistor. I'm still curious about the heatsink I have. It looks like it is made to pull over the transistor, like a cover. Is that a good/bad thing? Am I better off affixing it to one side of the transistor? Am I getting too darn nitpicky here? What is the meaning of life, and why is the sky blue?

hagtech · « **Reply #6 on:** 6 Nov 2005, 07:46 am »

I can see why you ponder the meaning of life, it has to be three friggin am when you wrote that!

Quote

looks like it is made to pull over the transistor, like a cover

Think of it as a condom. The idea is to get the heat to transfer to its surroundings. Not that much power dissipated in the transistor. Only issue is one of mechanical support. It should hang nicely, but if transported in a military vehicle for any length of time the vibration might fatigue the leads.

jh

markmaloof · « **Reply #7 on:** 6 Nov 2005, 08:25 am »

Yes, it is after 3 friggin' am, so to speak. My wife and I got back a little while ago from a midnight screening of "Capote" (we do things later here in NYC, except for those mornings when I have, say, a 6am call, ugh. Comes with the territory of working in video/film/tv production.)

I get a kick out of the condom reference, time to sexy up audio, hey?

markmaloof · « **Reply #8 on:** 6 Nov 2005, 08:48 am »

Hey Jim. If you happen to be reading this, I'm shooting you an email with one other question.