scanmail 10k short troubleshooting guide

The identification of a fault on the SCANMAIL 10K is simplified by the duplication of sections of the circuitry. In particular the selection of the RESERVE module will confirm whether a fault is local to the MAIN oscillator module or the front panel/MAIN PCB. Similarly, the removal of the filtered mains lead and selection of BATTERY mode will confirm whether the power supply is defective or indicate any interference is radiated or mains born.

Note that the battery is permanently floating across the power supply and only by removing the mains lead can the unit be completely isolated from the customers supply. This is particularly important at sites where heavy mains interference is suspected since the unit may alarm repeatedly. If, by removing the mains lead, this repeated alarm condition is cleared then it is recommended that the customer operate on battery or be offered a MAINS FILTER UNIT available from SCANNA. This interposes directly between the filtered mains lead and the unit and is supplied complete with matching connectors.

If the unit continues to alarm when in the 'floating' battery condition with no mains lead connected then there may be a strong radiating field close to hand. Examples of airborne radiation include handheld radio transmitters and arc welder.

Listed below for illustration are some possible faults together with the likely cause. If each check point is found to be in order proceed to the next listed.

THE USE OF COMPONENTS OTHER THAN THOSE SPECIFIED BY SCANNA WILL SERIOUSLY IMPAIR THE PERFORMANCE OF THE SCANMAIL 10K AND WILL INVALIDATE THE WARRANTY.

FAULT: The unit will not 'power up'.

The display is not illuminated.

Check the customers supply. Is the filtered mains lead firmly 'home' in the unit.

Check the filtered mains lead for continuity and a failed 3 amp fuse in the fitted plug.

Check the indicator on the internal Power Supply mounted on the bottom plate when the mains lead is connected. Since the power supply is short circuit protected, the fault is either due to a short across the power supply or within the power supply itself. Disconnect the internal power supply output lead at the main PCB and re-check the red power supply indicator. If this indicator is off then the power supply is faulty.

Check the internal 200 mamp fuse in the power supply. If this is intact suspect either a dry joint on the power supply circuit board or, the 110/220v switch wafer bearing directly on the copper track of the same circuit board. Return the power supply if in doubt.

FAULT: The unit will not operate on BATTERY.

The battery is a high duty cycle maintenance free. The module is comprised of bracket, battery and fibreglass retaining tape.

Check that the battery fuse has been fitted and is intact.

Check that the TAKBRO connectors are firm at the battery terminals. Check the voltage across the battery with the battery fuse removed. Note the battery charges automatically when the mains is present, hence if there is no improvement in the battery state after several minutes, it must be assumed that the battery is defective. This is unusual within 5 years but may be due to repeated use on battery and failure to switch off when not in use causing repeated exhaustion of battery capacity Complete battery module must be returned for replacement.

Fault: The display remains on MALFUNCTION, HOLD with the MAIN oscillator selected.

Check the main oscillator for correct envelope amplitude. Realign the module and test as described in section 5. Check that by switching off, selecting the RESERVE module, and switching on, the TEST status is achieved. Return the MAIN oscillator module together with the 10 way ribbon cable for repair, noting that the unit is designed to operate on RESERVE continuously, in the absence of a MAIN module.

Check the internal 9.6v DC is present on each module. The regulator is sited on the main board and is fed from the power supply or battery at 13.8v. Return the unit for repair.

Check that the relay, mounted on the front panel PCB, changes over when the front panel RESERVE switch is depressed. The relay driver transistor should be replaced. Check that inserting the reserve module and its 10 way lead into the main ''A'' oscillator position causes the TEST status to be achieved. The 10 way ribbon cable of the main oscillator module is faulty. Check the continuity of the upper and lower sensor lead connections. These must be connected in the right ''sense'' for oscillation to commence. Return the unit for repair.

Fault: The unit operates correctly but occasionally spuriously alarms.

Check that this condition is common to both oscillator modules. If this is not the case the fault may lie with the 10 way ribbon cable of the offending module.

Check the adjustment of the SENSITIVITY potentiometer of the suspect module. NOTE that if the SENSITIVITY potentiometer of a module has been adjusted to extreme then spurious alarms will result. Check if the unit is mounted on a large metal surface or that current carrying cables do not pass directly close underneath. The lower sensor coil of the unit will detect electromagnetic anomalies if they are in close proximity. It may also register vibrations in a large metallic surface on which it is mounted.

Check that by disconnecting the filtered mains lead from the unit and selecting battery operation there is no longer a problem. The unit is responding to a high level of mains born interference. The cause may well be adjacent heavy electrical plant such as a press. Simple observation of the area will often reveal the interfering source. The customer should be advised of the mains interference. A filter unit is available for just this problem and it plugs directly between the filtered mains lead and the unit. Resiting the unit electrically will exploit the attenation of the supply to mains interference and help to resolve the problem.

Check that there is no immediate evidence of electromagnetic radiation such as an arc welder or mobile radio transmitter. Where radiation is sufficient to be detected by the unit the possibility of re-siting the unit should be considered. Check the unit for loose connections particularly the 10 way ribbon cables to the oscillator modules. Return for repair.

Fault: The unit will not detect the TEST CARD when in TEST or OPERATE mode.

Check the operation of the unit on the alternative oscillator module. The alignment of the suspect module should be checked particularly the SENSITIVITY setting. Check that the alarm indicators on either side of the front panel flash momentarily. There is a fault on the main PCB associated with the detector. Replace the front panel module or return the unit for repair.

The above is not intended to be exhaustive but merely a guide to the verification and identification of a reported fault.

DO NOT USE COMPONENTS OTHER THAN THOSE RECOMMENDED AND AVAILABLE FROM SCANNA.