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When is a dead Argus 2 not really a dead Argus 2 ? Buying faulty cameras.

Posted: Sun Apr 17, 2016 3:45 pm
by Fraser
It is not uncommon to see Argus 2 cameras for sale on auction sites listed as faulty due to no image. Are these cameras worth buying or is it a challenging repair ?

Well my views are as follows.....

The Argus 2 is an excellent piece of electronic and mechanical engineering. It is built to take hard use in challenging environments and is generally reliable. Like all 'tools' it can fail due to abuse or age related component degradation.

The camera uses a very high quality BST imaging core with an excellent 320 X 240 pixel FPA and 60 fps refresh rate. It is well worth repairing such a camera. There are challenges however.

The whole camera is subject to certain dual use technology restrictions so information on its internal parts and circuits is almost non existent in the public domain. Some eBay auctions have provided tantalising views of the internal PCB's but nothing very helpful to a repair.

The camera consists of a Raytheon imaging core connected to a Raytheon controller board. EEV make the detector mounting PCB, display PCB and video/system control PCB. The video image is presented to a relatively standard self contained composite video monitor. The monitor contains the usual parts needed to create the image on a CRT and so failures in this module are eminently repairable by anyone with TV repair experience. The external video port on the camera provides a quick test point to determine whether the camera is producing a composite video image. The power supply for the cameras comes from a battery pack containing 8 AA cells.

The symptom of power present but no image being produced can have many causes. As no servicing information is available to the public it can be challenging to diagnose faults. Power supplies should always be checked for presence and sensible voltage levels. The dreaded capacitor failure can occur in any electronic product, causing havoc on its associated supply rail. Tantalum capacitors can fail as well as the infamous electrolytic types.

It is always useful to know if the chopper wheel is spinning and, as it spins up, whether it then regulates its speed. The chopper wheel helps to create the image by refreshing the sensor elements on the BST array. Without the chopper wheel the BST array will show temperature changes like a hand waving in front of the lens, but it will not see a static object that is at constant temperature after an initial detection of it. The object just fades away into the background. The chopper wheel can suffer age related degradation of the thin membrane material and physical damage due to the camera being dropped. The motor that drives the wheel is generally reliable. A beam break IR TX and RX sensor detects a thin notch in the wheels outer edge. This is used to feed rpm data to the camera electronics and synchronise the wheel to the BST sensors scan rate of 60fps

The Argus 2 contains an IRIS that is driven by a small motor. The iris is normally closed when the camera is off and it is used during camera operation to regulate the energy presented to the relatively narrow dynamic range BST sensor array. The iris can become stuck closed and so no image is present when the camera is running as it has been blinded by the closed iris. The iris comprises two metal leaves driven by a gear wheel. Bill has advised that oil from the motor can contaminate the leaves and cause them to stick closed. DO NOT thump your camera hoping to dislodge the iris leaves. Such is not likely to work, be a long term repair or be good for your cameras health ! Careful disassembly and cleaning is required.

Q. Is a dead Argus 2 worth buying ?

A. Yes if you are an experienced electronics repair practitioner who can also cope with mechanical components. These cameras are well worth repair. They are not suitable for beginners in electronics unless there is experienced help available to guide the repair and consider the fault symptoms.