SECTION 4
SERVICING
PRECAUTIONARY NOTES AND GENERAL INFORMATION
Routine Frequency Adjustments
This equipment uses quartz crystal control of its channel frequencies. Whilst this is extremely
reliable and accurate, it is important to realise that crystals 'age' slightly and require periodic
re-adjustment. The frequency count, and consequently the netting procedure, must be carried out
as a matter of routine at least twice a year. The requirement for this adjustment is independent of
equipment usage since the 'ageing' effect occurs even during careful storage, and is greater when the
equipment is new.
'Pozidriv' Screws
Where 'Pozidriv' screws are used in this equipment, only the correct size of 'Pozidriv'
screwdriver should be used to release or tighten these screws. The use of any other screwdriver type
can result in severe damage to the screwhead.
Servicing Compounds
Module pins are gold plated and are not subject to oxidation. Contamination from grease or
dust should be removed by the application of contact cleaning fluid only (such as R.S. Components
Ltd., Cat. No. 55
4
/
1
75). Under no circumstances should any abrasive or corrosive cleaning fluid be
used.
When active components mounted on heatsinks are replaced, a heatsink compound (such as
R.S. Components Ltd., Cat. No. 553/311) must be applied between the component, insulating
washers, and the heatsink surface to ensure a good thermal path.
Soldering
Keep soldering operations to a minimum
Ensure that equipment is switched off before soldering
Clean printed circuit tracks before applying solder or soldering iron
Keep the dwell time of the soldering iron and the amount of solder applied to the minimum
required for practical purposes
Use heat shunts to avoid excessive heat
Check that the hole in the printed circuit track is clear of solder before fitting a component
Use a low voltage DC soldering iron, with an earthed bit, wherever possible. This type of
soldering iron must be used when replacing a field effect transistor
Do not use a permanent magnet type soldering iron in the vicinity of coils with ferrite cores
Ensure that, when soldering wire ends into printed wire boards, solder flows through to emerge
on the other side of the board
Printed Circuits
Take particular care not to bend a printed circuit board when removing or replacing it or when
working on it. Bending can cause hairline breaks in the printed circuit tracks, and such breaks are
very difficult to locate. Do not connect test leads to a printed circuit track.
4.1
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