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AGEMA(FLIR) Thermovision 550 MWIR Cooled camera teardown and repair by Fraser

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Fraser:
Those who follow my posts will see that I recently purchased a second AGEMA Thermovision 550 (THV550) for £200. It was a calculated risk purchase as the camera was not sold as tested and the seller had nor means to power the unit. This worked to my advantage as the camera was originally listed for £1K but it had the potential to be an expensive paperweight if the cooler was dead. Negotiations with the seller ensued and I became the cameras new owner  :-+ I reasoned that even if the cooler was dead, the rest of the camera would be good spares for my other THV550 and such spares are very rare to find these days.

The THV550 arrived and was quickly connected to a power supply for testing. This model of camera does not have an internal power source in order to reduce weight and bulk. It is powered from either a battery belt or a mains PSU. When the power button was pressed, I was rewarded with the sweet sound of a rotary Stirling cooler that was not suffering mechanical failure. a good start that got better. After 6 minutes the cooler dropped to its "maintain" speed that is lower than the initial cool-down so quieter  :-+ 6 Minutes is good for these THV550 cameras so the cooler looks to be in good working order. This was great news as I can repair all the other parts of the camera.

When first powered, I noted an issue with the image displayed in the LCD colour viewfinder. The image was in monochrome when it should have been colour, and the image had a vertical sync line offset that meant the top of the image was now shown at the bottom of the display. After a reboot whilst still connected to the power supply, the issues both corrected themselves. If the camera was disconnected from the power supply, reconnected and restarted, the two display issues returned. I already knew exactly what the cause of this issue was and how to repair it. Apart from the EVF image issue the thermal image produced by the camera was excellent, as expected of a cooled MWIR camera.

My THV550 is a European PAL standard model that is fitted with a PAL standard EVF. These EVF modules are Ex JVC camcorder production and are mono-standard using a SONY chipset. The correct standard EVF has to be fitted to a camera of the same output standard for correct operation. If I had connected a multi standard video monitor to the THV550 I would not have seen the display issue. Confused ? Then let me explain as other owners of PAL THV550 and later PM series cameras will likely suffer the same issue in the future as the units age.

The fault: Colour EVF shows monochrome image and a vertical offset or no image at all (on later PM series cameras)

The Cause: Expiration of the Dallas DS1643 RTC lithium battery leading to loss of data from the battery backed RAM.

The reason for noted symptoms: The RTC RAM memory contains some camera configuration data that is read at Boot. If the data is corrupt or absent, the firmware loads a "factory default" configuration. The factory default configuration is stored in the cameras flash memory and is for NTSC standard camera. If a PAL camera suffers RTC data loss, an NTSC configuration is loaded at boot and the PAL EVF does not cope well with that , hence the monochrome image and vertical shift effect. Some EVF chipsets show no image or a course raster image only. Why does it fix itself after a reboot ? The camera firmware not only loads the NTSC default factory configuration but it also loads the correct PAL data into the RTC RAM ready for the next boot. Provided power remains connected to the camera, the RTC data is maintained and the next time the camera boots, its finds the PAL configuration data in the RTC RAM and loads the correct PAL configuration from firmware. If power to the camera is disconnected, the RTC loses its data again and the whole process repeats. The solution is to fit a new Lithium cell in the Dallas DS1643 RTC module. How do I know all this ? I completely reverse engineered the later FLIR PM570 that has its computer origins in the THV550  8)

The THV550 that I have just received was originally released in 1995 (mine in Circa 1996), 2 years before FLIR released their first Microbolometer based handheld thermal imaging camera in the form of the PM570. The two cameras share very similar case designs but the THV550 contains a stirling cooler in the location where the later PM570 located its internal Ni-Mh battery pack. The THV550 and PM570 have very similar computers in them so I feel quite at home working on this cooled camera :)

In this thread I will show the disassembly of the THV550 and the layout of its internal parts. Disassembly is almost the same for the PM570. I will also show where the RTC module is located and the BR(CR)1225 Lithium cell that must be changed. Once the Lithium cell has been changed, the camera will store the correct data in the RTC RAM at the next boot and the camera will operate in PAL output mode at subsequent boots. The Lithium cell life in these camera is very long and you can expect at least 10 years from the new cell. Note that the RTC module used in the THV550 and early PM570 cameras is the DS1643LPM (low Profile Module) socketed version that is nor intended to have a new cell fitted. It would normally be a module change out but these modules are long obsolete so a change of cell is the best way forwards. New Old Stock of the DS1643LPM will have unknown battery life remaining, and that is if you can find any stock ! Later PM series cameras use a DS1643P RTC module that makes use of "PowerCaps" that are easily changed. The module is soldered to the PCB and the power cap snaps onto the top of it. The PowerCap contains a BR(CR)1225 Lithium cell and 32KHz clock crystal. They are still available to buy or just the cell may be changed.

Fraser

Fraser:
Continued....

Including images captured of the EVF display on first boot and after a reboot with power still connected.

Fraser:
Disassembly begins....... only 4 screws need to be removed to separate the two halves of the case.

Care is needed to disconnect fragil ribbon cables that bridge the two halves of the case.

Fraser:
Continued......

Fraser:
Continued......

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