Tucson T-238 Assembly Manual Download Page 3

 

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 

 (red-red-red-gold) 

[  ] R2 10K 

 (brown-black-orange-gold) 

[  ] R3 10K 

 (brown-black-orange-gold) 

[  ] R4 10K 

 (brown-black-orange-gold) 

[  ] R5 10K 

 (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 

 (brown-black-orange-gold) 

[  ] R7 10K 

 (brown-black-orange-gold) 

[  ] R8 10K 

 (brown-black-orange-gold) 

[  ] R9 10K 

 (brown-black-orange-gold) 

[  ] R10 10K 

 (brown-black-orange-gold) 

 
[  ] Solder and clip the leads (10 total) 
 
[  ] R11 1.5K 

 (Brown-green-red-gold) 

[  ] R12 470 

 (yellow-violet-brown-gold) 

[  ] R14 10 

 (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 

 (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) 
 

Summary of Contents for T-238

Page 1: ...tended for use with the Dallas Semiconductor 1 Wire bus and any device that needs a serial connection Four push button switches and a Liquid Crystal Display LCD provide the user interface The initial application for the T 238 is a controller that accepts data from a Dallas Semiconductor weather sensor unit processes it and formats it for sending either directly to a Terminal Node Controller TNC fo...

Page 2: ...tor 1 2 w 5 Carbon Film 1 4 7 Ω yellow violet gold R13 Resistor Trimpot 1 10K Ω Trimpot 103 V1 Capacitors Capacitors may be marked in various ways The typical markings are listed but may vary Find all that match and the remaining ones if any should become apparent by elimination Mylar or Monolithic 5 0 1 uf 104 C3 C7 Electrolytic or Tantalum 5 1uF 105 or 1 35 C8 C12 2 10 uf C1 C2 Diodes 2 1N4148 S...

Page 3: ...ayout 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 ne...

Page 4: ...oldered connections or cold gray and or grainy looking solder connections OK so far This completes the IC socket installation Capacitors All capacitors should be mounted as nearly flush to the board surface as practical without stressing the leads Install the following capacitors C3 0 1 uF 104 C4 0 1 uF 104 C5 0 1 uF 104 C6 0 1 uF 104 C7 0 1 uF 104 Solder and clip the leads 10 total Electrolytic a...

Page 5: ...arked on the PCB with a square pad Pin 1 on the crystal oscillator is marked with a black dot and or an edge of the can that is square instead of rounded CAUTION Make certain that the U1 metal housing does not short to nearby R10 or R12 U1 32 000 MHz U2 9 8304 MHz Solder and clip the leads 8 total Connectors Gently rock the RJ 11 connector until it snaps into place and solder the leads J2 RJ 11 co...

Page 6: ...x16 pin male header with pins facing to the rear of the LCD module and in holes 1 through 16 NOTE J8 on the PCB is an alternate connection for powering the LED backlight on the LCD There will be a red and black wire a polarized Molex plug housing and two pins remaining These are for LCD displays that do not have a 16 pin header but rather a 14 pin header Pins 15 and 16 supply power to the LED back...

Page 7: ...as components heating up smoke or smell Remove power immediately if anything unusual appears Place the ground lead of your voltmeter on pin 2 of U3 This will be the ground reference for the rest of the measurements Measure the voltage on the voltage regulator U5 on the pin furthest from the power jack It should be between 8 and 14V If it is 0V then L1 is likely missing or damaged If it is low the ...

Page 8: ...t U4 Pin 2 Greater than 8V Check IC socket C8 C9 C10 C11 U4 Pin 6 Less than 8V Check IC socket C8 C9 C10 C11 Remove power from the T238 Locate the flat ribbon cable Notice that one of the leads nearest one of the edges is a bluish color compared to the rest This lead denotes pin 1 You may wish to place another indication of pin 1 such as a sticker on the connectors WARNING Polarity of the flat rib...

Page 9: ... not cause any damage but the unit will not work Some telephone cables reverse the wires and some do not In addition some telephone cord couplers reverse the wires Find a telephone cable that does not reverse the wiring Hold the connectors side by side and oriented the same direction for example the clip tab down on both connectors Observing the red and green wires inside If for example red is on ...

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