Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Question

[keeney123]

Re: Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Questi

I think the OP's decision to remove the thermal pad is because they "learned" from CPU "delidding" and other ridiculous ideas as to reduce thermal impedance. This is not acceptable for amplifier design because CPU heatsinks tend to be isolated from any electrical potentials (for desktops at least; laptops usually do have some constraints) and even if the CPU shorts to the heatsink, it may not matter as the heatsink is completely shrouded by the computer case.

Amplifiers do typically require electrical isolation between heatsinks and semiconductor devices due to sharing, if not also for electrical potential requirements since the heatsink may be exposed to the outside of the chassis or even *is* the chassis, as running the case at high voltage potential with respect to ground typically is not a good idea for UL approval.

So, what your saving is design matters on risk?

UL approval is good if the inspectors are honest.

My dad and the owner of his company once bought a UL inspectors approval with liquor and fast women. It had to do with being able to put 1200-foot lbs. of pressure down on a foot holder for an electrical connector in a mobile home electrical junction box. My dad was a plant manager of a sheet metal company that also made electrical junction boxes for mobile homes. My dad has been dead for 20 years.

[eccerr0r]

Re: Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Questi

usually these things won't fly, people will short the case to what they think is GND and get a large spark and kill the device... getting RMAs for this is a waste.

There's a lot of things that aren't obvious right away trying to save a few cents to make the heatsink at the same potential as the collector. Just that designers/beancounters trying to save a few cents for that insulator better think long and hard to justify saving the cents... and hence end users should trust the designers that they considered not including it too.

[keeney123]

Re: Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Questi

usually these things won't fly, people will short the case to what they think is GND and get a large spark and kill the device... getting RMAs for this is a waste.

There's a lot of things that aren't obvious right away trying to save a few cents to make the heatsink at the same potential as the collector. Just that designers/beancounters trying to save a few cents for that insulator better think long and hard to justify saving the cents... and hence end users should trust the designers that they considered not including it too.

I am abbreviation challenged RMAs?

Good point I did not consider the beancounters trying to save a few cents. So many angles to consider.

[nobbnobb1]

Re: Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Questi

Wow I really didn't know I'd be opening up such a can of worms!

I decided to play it safe and clean up the thermal pad for re-use. It's not damaged at all and I also used a thin layer of thermal grease on each side to help it a bit. Everything works fine and runs cool. Glad I caught this earlier and didn't take any chances powering it up without the insulator. Nothing wrong with being conservative.

[keeney123]

Re: Fixed a Velodyne DPS-12 Subwoofer. Thermal Management + Heatsink Grounding Questi

Wow I really didn't know I'd be opening up such a can of worms!

I decided to play it safe and clean up the thermal pad for re-use. It's not damaged at all and I also used a thin layer of thermal grease on each side to help it a bit. Everything works fine and runs cool. Glad I caught this earlier and didn't take any chances powering it up without the insulator. Nothing wrong with being conservative.

I would follow the unit long term for failure or the transistors. Let's say 5 years and then get back to this thread to report if successful.

No can of worms opened just input from different people with different experiences in the electronic field.

You ultimately made your own choice on how to handle the situation after considering the feedback. That is all any teacher can ask from a student.