The EnviroScope atomic force microscope (AFM) combines enhanced environmental controls within a sealed hermetic sample chamber, and the world's most advanced scanning technology to deliver greater application flexibility to research and industrial laboratories looking for a competitive edge. The system allows observation of sample reactions in a variety of complex environmental conditions, including high vacuum, liquid, and gas purge and exchange, as well as high temperature and fluid heating. Based on the industry-standard Dimension AFM head, the EnviroScope scanner provides proven scanning probe performance and reliability while performing an extensive range of imaging modes, from contact AFM and magnetic force microscopy to patented techniques like TappingMode AFM and PhaseImaging.[Veeco flyer on EnviroScope AFM, 2005]
One morning the microscope stopped working. After any attempts to initialise the stage the software was returning an error message. The microscope did not respond to the controller commands. Any attempts to reboot the system or power cycle it did not result in any success. Then the equipment manufacturer was contacted, but it turned out that Veeco sold their microscope business to Bruker in 2010. However, Bruker did not have any engineers to help with the repair as the system was already obsolete. Instead they suggested one of independent AFM repairers. It took a long time to get their engineer to look at the system. But in the end no solution was found. Hence, the repair process got stuck.
At this stage I decided to take a look at this issue in a hope to reinstate the microscope. Unfortunately, there was very little documentation available on the system components and hardware. The only available documentation was the User Manual on the system. Below is how the system looks like. Apart from the microscope body it has the NanoScope IV controller, NanoScope EnviroScope controller, temperature controller and power supply. The microscope control and imaging software runs on a PC under Windows XP.
First, I decided to work out what part of the system fails. Because the Stage Initialise command results in the stage movement, the lack of response could be caused by some failure in the chain between the PC and the piezo motors. However, the piezo motors are connected to the EnviroScope controller which in turn is connected to Cable-2 connector of 8-port PC controller. Hence, the failure could be caused by the following: PC port malfunction, EnviroScope controller hardware, stage drivers, motorised stage.
In order to locate the fault I first decided to look at the serial port communication between the PC and EnviroScope controller. As the communication speed was unknown, I first tap the Rx and Tx lines with an oscilloscope probes. This revealed some discrepancy in the communication. The PC was sending data at 19,200 baud speed, while the controller was sending data at 28,800 baud speed. Obviously that resulted in permanent communication erros. It was possible to directly eavesdrop on the RS-232 communication with a laptop PC. However, no meaningful information was trasferred since the protocol was propritary.
The next step was to look inside the EnviroScope controller to work out why it responds at a different speed. Hence, it was opened for a quick look inside. There was not much in there - just two printed circuit boards. One with the Motorola microcontroller and another with the logic and piezo drivers.
To find the problem inside the controller, first the power supply lines were tested and found satisfactory with 12.5V and 36.2V supplied. Then it was found that the core microcontroller, Motorola MC68HC11F1 in PLCC68, can only run code from the external memory. As the firmware setups the communication speed it was very likely that some of the code was corrupted. There was no memory on the main board, hence, it was fetching the code from the drivers board. With all the cablings and connectors along the way this could be the likely cause of the troubles.
To eliminate the possible issues with poor connectors, both the ribbon cable connectors were unplugged and then plugged back. However, that did not solve the problem. Then the main Motorola microcontroller was pulled out of the socket using PLCC extractor and then plugged back. After powering up the system everythig was back in operation.
The whole system was assembled back to be used as a fully functional microscope. Finally the microscope was fixed in a few hours time.
The next step would be to update the PC system, because the software was running too slow and the PC tends to hang from time to time. Because the software can only run under Windows XP this poses some challenges. Mainly because modern PC systems only support Windows 7 and newer versions of Windows. Unless the software for this microscope can run under Windows 7. However, there might be some issues with the driver card for NanoScope IV controller. This is something to figure out in the coming days.
<Sergei.Skorobogatov (at) cl.cam.ac.uk>
<Sergei.Skorobogatov (at) hushmail.com>
created 26-06-2017 -- last modified 27-06-2017 -- http://www.cl.cam.ac.uk/~sps32/