k4900 / k5515 toasted goodness!

patrick99e99

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Hey everyone... So I recently got a 720 with a k5515 chassis, and the corner of the board near "vertical out" was completely fried and broken off... I found someone selling a chassis on ebay, so I bought it.. when I got it, I looked and that location on the board, although not broken off, is totally charred and roasted.. I then looked at my Tron that has a 4900 (very similar board) and that same corner, roasted and toasted! Then I looked at my Space Ace which ALSO has a 4900, and same thing toasted roasted corner!!... I also noticed on the neckboards of all these, the molex connector is right next to a huge resistor, and all those molex connectors are roasted and burned, plastic melted...

I looked on ebay at other k4900 and k5515 chassis being sold, and from what I see in the pictures, they ALL have the same thing going on ... Roasted, toasted crunchy corners ready to fall off, and melted molex plastic connectors!


I just am wondering if there are any recommended modifications to save these boards from what seems to be a very common issue... I was wondering about doing something like moving those resistors off to separate board with lots of space, and maybe using resistors with higher wattage values...?

Attached is a picture of one of the 5515's on ebay right now-- as you can see, a corner ready to break off...
The others are from my recent purchase, you can see the nice rich natural board color by "int face" vs the crispy burnt corner by "vert out".. And also the charred molex connector, and also the 3 resistors on the neck board are also somewhat charring the edge of the neck board.
 

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Heat is definitely no friend of time and plastic. Over the years, I've seen people mount items higher on the PCB (whatever they're working on), install parts on the PCB back, use heatsinks, and use shields. Some of those may work in your scenario.

I wonder if heat tape would work long term? I use it during surface mount work to protect other nearby parts from the heat gun heat.

Scott C.
 
Yeah, those resistors need to be cooled, either actively with a fan maybe or passively by mounting to a block of aluminum?
I have two toasty 4900s myself and have been wondering what to do about that VERY warm corner.
 
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