Behind the Main System Panel
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The design of our spectrophotometry system allows for many problems to be diagnosed by us remotely and subsequently repaired by the user under our instruction. The obvious benefits of this approach are the relatively low cost and short time scale over which an effective repair can be implemented. This will often result in a remedy within twenty four hours at little or no cost to the customer.
If the problem is diagnosed to be in a particular module (e.g. an input amplifier or photomultiplier power supply) then the faulty module may be readily released (by simply undoing the appropriate mounting screws) and unplugged from the system backplane. Most problems are caused by integrated circuit (I.C.) failure. All the I.C. chips on our boards plug into sockets, and therefore replacing them with new devices is a very simple task. If replacing the appropriate devices does not resolve the problem then the module can be returned to us for further checks without disrupting the rest of the system.
With systems supplied from January 1994 onwards, the main system electronics are also modular with five separate boards taking care of different aspects of system control. The diagram included with this leaflet shows a schematic representation of these boards as viewed from the system front panel. As with the plug-in modules, it is often possible to isolate a problem to a particular board remotely. Access to these boards requires more time and attention than to the plug-in modules, but is still relatively straightforward if the following instructions are followed:
- Unplug the system box from the mains and ensure that it is located so that the top can be removed. It is advisable not to unplug the rotor wheel if this is possible.
- Remove the four (two on each side of the enclosure) black socket head screws from the top of the system box, using an appropriate allen key.
- Remove the three screws, which retain the top edge of the sytem box back panel.
- Fully loosen all the screws from the top of the front of the system box (the number of these will depend on the configuration of the system).
- Remove the top of the system box. This may be facilitated by releasing and partially removing plug-in modules from the top row of the system enclosure.
With the top removed the five boards in the diagram can be seen. Direct access to the frequency generator board is possible from above. The power supply board is made fully accessible by unplugging the frequency generator form the front panel and the system backplane. Loosening the front panel will allow any of the other three boards to be removed from the system backplane. As configuration details and board versions may be subject to variation, it is important that careful note is made of any connectors removed or jumper links altered in accessing the boards or subsequent operations.
User repair / alterations will normally take one of the following forms:
Replacement of one of the system fuses. These are all located on the power supply board. This board should never need to be removed but can be readily accessed as described above.
Replacement of a socketed I.C. chip. A replacement chip will be sent together with a description of its location. I.C. chips are best removed with a small screwdriver or tweezers applied at either end to loosen and remove the chip from its holder. Care should be taken when inserting the replacement that all pins are correctly seated before pressing the device firmly into place by hand.
Relocation of jumper links to alter the system configuration or to set up test conditions.
More specific details will be supplied as appropriate.