Ezee Controller Mosfet Heatsink Spring Clip Reassembly Tips?

[drongo]

The subject seems to cover the issue.

After 2yrs1mo1day, the high side mosfet shorted in my eZee controller. Since I was running a 48V pack, I'm surprised it didn't blow earlier, but it has been pretty hot lately.

I've replaced the shorted fet, but after everything is in place, I'm hesitant to force things in case I break something.

Has anyone here travelled down this path before? There is a large aluminum T-sink between the backs of the fets. A metal spring clip inserts into holes in the pcb, and when it is properly seated below the lip of the underside of one side of the T-sink, presses on three of the six fets and forces them into secure contact with the sink. Same for the other side.

Should I firmly tighten the screws that anchor the T-sink onto the pcb, and then just force/pry each clip under the lip of the T-sink? Or is there a more elegant way that doesn't risk stripping the mounting screws? (screws mount from underneath board as shown in attachment)

 

[drongo]

In the process of crafting my question, a few more ideas occurred to me, and one of them worked!

I will document it when my batcycle is roadworthy again.

cheers,

drongo

 

[drongo]

I will write this up while I'm waiting for the conformal to dry.

1. don't install the mounting screws until after you've seated both clips into the t-sink. You need to be able to rock the t-sink to allow the clips to be seated.
2. insert the clips into their respective holes in the pcb
3. don't forget to insert the thermistor into the hole in the t-sink before re-installing
4. lay the insulator material back on the pcb, ensuring the holes line up.
5. insert the t-sink between the mosfets and align it with the mounting holes. (see 4)
6. to seat the clips on the side of the t-sink closer to the middle of the pcb, rock the t-sink carefully towards the outside of the pcb, just enough to permit the clips to fit under the t-sink lip. Use a flat driver, long metal tweezers, or other tool to push all the clips at once under the lip. Make sure you don't move the t-sink sideways, only rocking back & forth.
7. Once the inboard clips are seated, rock the t-sink forward and down, to ensure complete seating of all clips.
8. Find a piece of metal, stainless preferred, but steel, or alum will do, and approx. the length of all three spring clips and the same height.
9. place metal square against side of all three clips, pivoting against edge of pcb, until all three clips are seated.
10. The above step is tricky, and so you need to maintain a backwards pressure allowing the clips to fit under the lip, but at the same time be ready to push down towards the pcb as soon as they are in place.
11. once both sets of clips are seated, and the t-sink is perpendicular to the pcb and in line with the holes, install both mounting screws (with their insulating washers), and the job is done.

If you know how to solder, replacing a mosfet is simple. Reassembling the heatsink spring clips is the difficult part, and hopefully is now easier.

cheers,

drongo

 

[Ndog]

Sorry to revive an old thread. I am replacing the fets in my dead Ezee controller described here, but I mangled the thermistor that is set into the heat sink. I want to replace that too, does anyone know what kind it was?
Thanks