RAT5 Manual version 1.2.0
RAT5 Information Manual version 1.2.0 © GW4GTE 2010
Page 11 of 29
3. Construction
Before you start
(Tick when done)
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Make life easy for yourself by clearing a good sized work-space on the
bench. You’re going to need a pair of thin-nosed pliers, some side-cutters
and a good soldering iron with a small tip fitted e.g. Weller. A tip temperature
of 700C (Weller tip number 7) is recommended, as is the use of ‘proper’
60/40 flux cored colder. Use 22swg solder if possible. Anything thicker is
almost certain to bridge tracks.
A bench vice or ‘helping hands’ may be useful for holding the PCB during
assembly and a stamp loupe is handy for checking your work and inspecting
tracks. Maplin sell a range of these.
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Print out the parts list, circuit diagrams and PCB layout from the appendix at
the end of this document and keep them to hand.
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Check the components supplied against the parts list. You may wish to
arrange them in some sort of order as you proceed to ease identification
later.
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Inspect the PCB. In the interest of cost the boards have been produced
without a solder resist layer or a silk screen layer. Careful soldering and a
logical assembly order make these features non-essential. Hold the PCB up
to a suitable light source or simply hold up to the sky, looking from the copper
side, then check all holes are drilled. The boards will have been carefully
checked but as they are hand-drilled there is always the chance a hole could
be missed. It’s easier to correct any problems now rather than when the PCB
is half populated.
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Before soldering anything, offer the following parts to the PCB to check for fit:
T1 and T2, L1 and L2, RV1, 2 and 3 and FL1. Also the board connectors
marked as PL1, PL2 and PL3. Note you may need to snip the header strip
supplied to the correct length. T1, T2, L1 and L2 have two screen tabs. Only
one is used. Identify which is unused and snip off. The same tab is unused on
all four components.
Start Soldering
The project is PCB based and no surface mounted components are used, making
construction quite straightforward.
First though a few words about soldering. Don’t use the soldering iron as a solder transport
system (You don’t want to start off with a big blob of solder, or burn off all the flux before you
get to the joint and the connections to be soldered should be up to temperature before they
see the solder). The two parts of the joint should be mechanically touching (as far as is
possible with PCB track and components) then heat applied from a clean, tinned-tip iron for a
couple of seconds. Then apply solder to the site, letting the iron heat the job properly to give a
smooth solder flow. Then remove the iron, taking care to lift the iron vertically away to reduce
the risk of bridging to an adjacent track. Don’t rush it – the components are designed to take
the heat.
