Reviving a vintage Transmission Electron Microscope - The Philips EM 420 (part 1).

Figure 1. A fully functioning Philips EM410, I helped bring back to life a
few years back. It is a lot like the EM420, but made more for biological
applications.

I have been wanting to write some essays on Electron Microscopy for a while. So considering the amount of experience I have as a Transmission Electron Microscope (TEM) service engineer (13 years), I figured it would be fun to write about bringing a excellent scope back from the dead. The EM 420 came out sometime in or before 1983, according to an advertisement in the June 16 1983 edition of New Scientist (1). It can resolve down to 0.20nm (2 Angstrom), magnify up to around 800,000X, operates at 20 to 120 Kilovolts and is an excellent workhorse scope still economically viable and remains in use in some labs (2,3). So join me as I bring this guy back to life, and explain a few things about the science and engineering behind it on this journey, with LOTS of photos of its guts!!! It may take a while to bring it back, since it has been about a year since this thing was running. Also, I have service calls to attend to, and other projects on the side. When it is all dialed in running as it should, I will put a camera on it that we made and take some cool pics of some industry standard reference materials. If I can get my hands on the right sample prep equipment I will image other things.

But first…...

If you are new to Electron Microscopy, let me get you caught up on a few things. It is a massive field, with a long history, but I am going to be pretty brief.

First of all...Why?

Electron microscopes enable us to see details extremely smaller than with light microscopes. For example, the maximum magnification achieved with light is around 2000X, whereas with many commercially available Electron Microscopes magnifications of over 500,000x can be achieved. Okay...so what can we see with that? Well for example, viruses, bacteria, fine details of pollen, functional motifs of macromolecules like proteins which are nano scale machines and structures and all the way down to atoms! More important than magnification, is vastly improved resolving power, or in other words the ability to distinguish two different objects.

For comparison:

The unaided human eye can see separations of 0.1 mm, but with a good light microscope 100 nm can be distinguished (4). With the most powerful commercially available electron microscopes features as close as 55 picometers (0.055 nm) apart can be observed (5).

Now a little history

The first Electron Microscope was created by physicist Ernst Ruska in 1931 with his electrical engineer mentor, Max Knoll . That scope could resolve details down to 10 nm, and then sometime in the 40s resolution was increased to 2 nm (6) . These scopes were all Transmission types where in short the electron beam is focused through the specimen, and the resulting image focused onto a phosphor screen that converts the electron information into visual light information, an image. The first scanning electron microscope was constructed by Manfred von Ardenne in 1938, and patented in 1944 by RCA (7, 8). Scanning types collect information from the electrons bouncing off the surface of the sample, and convert it into an image. There were several other people involved in the development of electron microscopes in the early days and I will discuss what they did further on.

How these magnificent instruments work I will explain in upcoming posts. Right now tho I want get started on getting this guy back up and running! But before I continue, I want state that these things are no joke to install or repair. ALL TEMs are top heavy, and weigh near a ton, or several. They draw a lot of current and can be dangerous to work on. You better have a solid understanding of electricity, and a great mechanical aptitude, before you even think of doing this. Last, but not least, I take no responsibility for whatever happens if should someone injure themselves after reading my blog!

Figure 2. Preparing to lower the scope down onto its feet.

The smaller TEMs like this one are usually transported by pallet jack into the room they will remain. This guy has his own screw jack system. I slowly lower each side by about 1/4" at a time until it rests on the floor. The next step will be connectiong the power unit in the back.

*Figure 3. Power Unit and connections.

Pretty straight forward this part. Once all electrical connections are made I usually proceed to connecting water lines, but I am going to bypass that for the moment because I want to see if it powers up. After that I will disconnect it from the 220V 40 Amp service it has and connect the water lines, and check for leaks.

Figure 4. Powered up!

Figure 5. Close up of mag display, this goes up to 800,000X!

Figure 6. The whole deal.

Not a bad start at all, most of the panel lights are on, and the digital readouts function. The roughing pump even turns on! More on the vacuum system later. So I am going to turn the guy off for now, and get back to it later next week. I have a LOT left to do, including remount the gun chamber,but first I am going to clean it up real nice!

P.S. If anyone knows of a Dimpler or Jet Electropolisher that are being junked, please let me know. I would like to do some metallurgical analysis with this scope.

Til' next time!

*Edit: For some reason I cannot renumber my last 2 references. Sorry! Should be 7 and 8.

References:

1. New Scientist June 16th 1983 Page 769

2. https://www.ncfl.ictas.vt.edu/?page_id=109

3. Pre-installation and installation instructions for EM420, PW6007 – Philips Electron Optics Eindhoven, Netherlands (sometime in the early 80s)

4. Zworkyn, V.K. (1945). Electron Optics and the Electron Microscope. New York: John Wiley & Sons Inc.

5. https://www.jeolusa.com/PRODUCTS/Transmission-Electron-Microscopes-TEM/300-kV/JEM-ARM300F

6.https://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/materials/public/ElectronMicroscope/EM_HistOverview.htm

1. Key events in History of Electron Microscopy. F Hagenau, 1 P.W. Hawkes, Microscopy and Microanalysis #9 2003

2. US Patent #2,348,030 - Scanning Type Electron Microscope