T-238 Assembly Manual
Rev. 1 February 2001
Page 3 of 11
Construction Notes
You are now ready to begin construction of the T238.
Follow these standard construction practices when building
the unit.
Use a temperature-controlled, fine-tipped soldering iron of
relatively low wattage (25 watts maximum, 15 watts is
ideal) and a good quality 60/40 or 63/37 rosin-core solder
for construction. Keep the tip of your soldering iron bright
and clean, wiping it frequently on a wet rag or sponge.
Make solder joints carefully, but swiftly. Prolonged heat on
a PC board pad can be as disastrous as it can ruin the PC
board. Two to three seconds should be enough time to
apply heat to any joint. Due to the proximity of some of the
traces on the PC board, solder bridges are a very distinct
possibility. Following the important points above could
eliminate several hours of troubleshooting (or worse). This
is good practice when working on any kit.
You will need small flush or semi-flush cutting pliers and
small-tipped long nosed pliers. A magnifying glass may
prove helpful to identify the values of the small
components.
Pay careful attention to the directions that follow:
1) Read this entire document prior to starting construction
of your kit.
2) Identifying the pins on headers and ICs - Pin 1 is
identified by the square pad on silk-screen.
Electrostatic Protection
The Integrated Circuits and crystal oscillators are
susceptible to static discharge. Observe anti-static
precautions when assembling the T-238. Never handle the
ICs without grounding yourself, the protective foam, and
the PCB first. Always touch and hold the foam first before
touching the IC. Always touch and hold the printed circuit
board before inserting the IC into its socket. Never leave
the ICs on anything but the foam or the PCB.
Construction
Refer to the layout diagram for clarification of parts
placement. All references to up, down, left, and right
assume that you are looking at the PCB with the text right
side up, that is the four switches are at the “bottom” and
the five big connectors are at the “top”.
Resistors
Resistors have a lead spacing of 0.4" and should lie flat on
the PC board. You may wish to use a lead former to pre-
form the resistor leads for neatest appearance.
NOTE:
–
Save the clipped leads as you will use them to
solder the ferrite beads in place in a later step.
Install the following resistors:
[ ] R1 2.2K
Ω
(red-red-red-gold)
[ ] R2 10K
Ω
(brown-black-orange-gold)
[ ] R3 10K
Ω
(brown-black-orange-gold)
[ ] R4 10K
Ω
(brown-black-orange-gold)
[ ] R5 10K
Ω
(brown-black-orange-gold)
WARNING!
–
Be careful when clipping leads, as they have
a tendency to fly towards your eyes! Take appropriate
precautions (grasp leads and wear eye protection).
[ ] Solder and clip the leads (10 total)
[ ] R6 10K
Ω
(brown-black-orange-gold)
[ ] R7 10K
Ω
(brown-black-orange-gold)
[ ] R8 10K
Ω
(brown-black-orange-gold)
[ ] R9 10K
Ω
(brown-black-orange-gold)
[ ] R10 10K
Ω
(brown-black-orange-gold)
[ ] Solder and clip the leads (10 total)
[ ] R11 1.5K
Ω
(Brown-green-red-gold)
[ ] R12 470
Ω
(yellow-violet-brown-gold)
[ ] R14 10
Ω
(brown-black-black)
[ ] Solder and clip the leads (6 total)
NOTE:
R13 is a ½ watt resistor. It is slightly larger than all
the other resistors. The lead spacing is 0.5”.
[ ] R13 4.7
Ω
(yellow-violet-black-gold)
[ ] Solder and clip the leads (2 total)
Now check your work. All leads should be soldered. There
should be no solder bridges or cold solder connections.
[ ] OK so far.
This completes the resistor installation. You should have
no remaining resistors.
[ ] No resistors remaining.
Diodes
Diodes are polarity sensitive devices. Diodes are mounted
flat near the surface of the board like the resistors
previously installed. The cathode end of the diode is
banded and corresponds to the banded silk-screen legend
on the PCB.
Install the following diodes:
[ ] D1 1N5817 Schottky
[ ] Solder and clip the leads (2 total)
[ ] D2 1N4148
[ ] D3 1N4148
[ ] Solder and clip the leads (4 total)