TAZ 6 RAMBo 1.3L Heat Sinks

Can someone clarify this?

I bought a TAZ 6 a few months ago with a serial number in the 24000 range. I was about to start a 20+ hour print but ran across several comments on the internet about issues with the Z axis controller overheating due to its heat sink falling off. To prevent possible damage to my unit, I decided to open the box and check this out before starting the print. To my surprise, there were no heat sinks on the board at all! The board is a RAMBo 1.3L. Further checking into this revealed a Lulzbot service bulletin instructing owners of earlier units to remove the heat sink entirely.

So I am a bit confused.

  1. Was it determined that the factory heat sinks caused problems and simply were not needed?
  2. Was there a board change to correct this that didn’t require heat sinks (does the “L” in the version refer to Low Power or something)?
  3. Are TAZ 6 units supposed to be shipping without heat sinks now?
  4. If so, any benefit to adding them back on with proper thermal transfer adhesive?
  5. Can I run my 20+ hr print without heat sinks safely without risk of damage or decreased life of the motors/electronics?


  1. They fall off and short the board sometimes, and with a proper fan they aren’t necessary.
  2. No, L is the version after version K. The motor drivers don’t get all that hot if you have a cooling fan on them.
  3. Yup. The new OHAI kit pictures for the latest assembly instructions does not show them https://ohai.lulzbot.com/project/taz6-control-box-assembly/taz-6/
  4. Longer motor chip life assuming they don’t fall off and destroy your void, also that would probably actually void the warranty.
  5. Yes, unless you put the control box inside an enclosure which will melt it even with the chips so don’t do that.

Thank you Piercet for the clarification. I did see the assembly instructions you linked to, but that actually added to my confusion. In section 6, it shows the heat sink installed and even labels the IC (U17) in the first picture. It leads one to believe that there is an important step involving that IC and the heat sink but there is no mention of U17 in the instructions, so perhaps they just have outdated photos, but still… confusing.

I got a bag of the small heat sinks for Raspberry Pi boards and proper thermal adhesive. It’s really tempting to just add them to keep everything cooler. Then again, the RAMBo board is less than $200 so it wouldn’t be a huge expense to replace if it failed after years of use… I would like to keep my warranty in tact.

Oh decisions, decision…

I have replaced more RAMBo boards due to the heat sink falling off and shorting something than ones that died due to heat damage. The chip does have built-in thermal protection. If you have issues with the thermal protection causing dropped steps then you might add the heat-sink then.