McClean: PlasmaPreen ORingReplacement

Overview

If you notice when using the Plasma Preen that you get plasma but it seems "locked" (i.e. you see a pink-purple glow but it is not moving) the problem could be that the antenna (fan at the top of the chamber) is no longer turning.

It is possible that the fan has stopped turning because the O-ring that is used as a pulley to turn it has worn down and snapped. This protocol will explain how to take the Plasma Preen apart and replace the pulley.

If you have pretty pink-purple plasma but it isn't moving your antenna might not be rotating. "Locked" plasma won't give you a good bond between PDMS and glass. Apologies for the reflection in the microwave door.

Materials

You will need the following to change the brushes in the lab roller drums:

• New O-Ring (#263 O-Ring)
• Philips head screwdriver
• Small flathead screwdriver
• Pliers or wrench
• Super glue
• Razor blade

Protocol

• TURN OFF THE PLASMA PREEN AND UNPLUG EVERYTHING.

• You are only going to be dealing with the "microwave" part of the plasma preen, so unhook the tubing at the body of the microwave (see picture). These should only be finger-tight, so you should not need a wrench.

Remove the glass bell jar from inside of the Plasma Preen (don't forget this costs >$800 to replace, so put it in an uber safe spot). Once the bell jar is safe, maneuver the Plasma Preen to a clear work space where you have plenty of room to get on all sides of it.

• Remove the black case of the microwave
  • You will need to remove the handle to the analog power regulator (see picture). This can be done using a small flat head screwdriver and loosening the two screws. Then use the pliers or the appropriate wrench to remove the nut holding the potentiometer to the case.

Green wire is grounded to the back cover. If you are careful you can work around it.

• • Remove the screws holding the case on. There are 5 screws on the back of the unit and one per each side (7 total, 5 silver, 2 black). There are 4 plastic brackets on top of the microwave that need to be removed. Place the screws and brackets in a beaker, or similar, so that you don't lose them.

Green wire is grounded to the back cover. If you are careful you can work around it.

• • Slide the case back and off. NOTE: The potentiometer is a pain to deal with. You can gently push its shaft through the case in order to get the case off.

• Check the pulley. The pulley is quite obvious and is right at the top of the machine. Check if it is broken or off of its track. If broken, remove the broken pieces and throw away.

• Replace the pulley.
  • Take a #263 O-ring and cut it with a razor blade.
  • Wrap it around the pulleys and determine how long it needs to be. Note that it doesn't have to be particularly tight as the antenna moves very easily. Cut the pulley with the razor blade so that when the ends are held together it is the right size.
  • Glue the two ends of the O-ring together with super glue. Allow to dry.
  • Place the O-ring around the pulleys.

• Reassemble the plasma preen.
  • Start by maneuvering the potentiometer into position (get the shaft through the case). Secure it with the nut. Note that it is easiest to make sure it is in the fully off position, that way you know how to put the knob back on such that the white indicator line actually points at approximately the correct place (power range 0-100%).
  • Slide the case into place. There are brackets on the top and both sides. These will click into place. If the case isn't fitting smoothly it is most likely because these are not appropriately aligned. Don't force it. Just back up and try again taking careful note of where the brackets on the case are and how they should align with the body. Seriously don't force it. It will happily slide into place if you line everything up correctly.

• Reattach the tubing from the vacuum and the gas source to the back of the microwave.
• Replace the bell jar.

Helpful Links

• Plasma Preen Manual

Notes

Please feel free to post comments, questions, or improvements to this protocol. Happy to have your input!

1. List troubleshooting tips here.
2. You can also link to FAQs/tips provided by other sources such as the manufacturer or other websites.
3. Anecdotal observations that might be of use to others can also be posted here.

Please sign your name to your note by adding '''*~~~~''': to the beginning of your tip.

*Megan N McClean 17:11, 19 May 2017 (EDT): I didn't take enough pictures while I was disassembling and reassembling the Plasma Preen. If you find it necessary to replace the O-ring, please take more pictures particularly of how to cut and replace the O-ring and how to get the analog power meter into place.

Contact

• Megan N McClean 14:01, 19 May 2017 (EDT)

or instead, discuss this protocol.