Tucson T-238 Assembly Manual Download Page 8

 

T-238 Assembly Manual 

Rev. 1 February 2001 

Page 8 of 11 

Next you will insert U3 and U4.  Make sure you match the 
pin-1 notch of the device to the notch on the silkscreen.  
There are a lot of pins on U3 and it can be difficult to line 
them up with the socket.  Your best bet is to place the chip 
sideways on a flat static-safe surface so that one row of 
the pins all lie flat on the surface.  Carefully rotate the body 
of the IC while pushing down on the pins.  Rotating while 
pushing down should bend all the pins together and bend 
them where they protrude from the body.  Bend the pins a 
little at a time, then check to see if they are perpendicular 
to the body of the IC.  Once perpendicular, the pins of the 
IC will be much easier to insert as they line up with the 
socket.   
 
Insert U3 slowly.  Observe that all the pins slide into the 
socket.  Watch for pins that bend under the IC or out of the 
IC socket.  Follow the same process for U4. 

 

[  ] Insert U3, MC68HC908GP32 
 
[  ] Insert U4, MAX232 
 
[  ] The notch on the chip is aligned with the silkscreen 
notch on the PCB. 
 
[  ] Apply power to the T238.  LED DS2 will flash three 
times quickly, and after approximately 10 seconds it should 
start flashing once per second.   
 
If LED flashes after approximately 30 seconds and then 
flashes once every three seconds, either OJ1 in the wrong 
position (jumper between pins 1 and 2) or you have the 
crystal oscillators swapped.  If the jumper is in the wrong 
position, power down the T238 prior to changing jumpers. 
 
If the LED does not flash at all, check OJ2 (jumper 
between pins 1 and 2).  If the jumper is in the wrong 
position, power down the T238 prior to changing jumpers. 
 
If the LED still does not start flashing, make sure that all 
the pins in U4 were inserted cleanly into the socket and 
check the following components carefully: R1, R2, R3, R4, 
R5, and R6.  Do not proceed until the LED flashes as 
described above. 
 
[  ] LED flashing approximately once per second 
 
With a the ground lead of your voltmeter on pin 15 of U4, 
check the following voltages: 
 

Check  Pin 

Voltage 

Remedy 

[  ] 

U4 Pin 16 

+5 

Check IC socket 

[  ] 

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 ribbon cable must be 

observed.  Pin 1 of the LCD display must match pin 1 on 
the PCB. 
 
[  ]  Plug the flat ribbon cable into J10; line up the bluish 
stripe of the cable with pin 1 on the silkscreen.  Pin 1 on 
the PCB is identified with the square pad and silk screen 
square around it.  It is the closest to U5, the voltage 
regulator. 
 
[  ] Plug the other end of the flat ribbon cable into the LCD.  
Line up the cable bluish stripe with pin 1 of the LCD 
module.   
 
[  ] The flat ribbon cable should lay flat and not twist or 
bend when connecting the PCB to the LCD. 
 
[  ] Cable installed with marked wire next to Pin 1 on T238 
and LCD. 
 
Place multi-meter in Ohms mode.  Measure the resistance 
between U3 pin 2 and pin 1 on the LCD module.  The 
resistance should be less than 1 ohm.  If not, the cable is 
either bad or installed backwards.  
 
[  ] Resistance from U3-pin 2 to LCD pin  1 is less than 1 
ohm. 
 
[  ] Measure the resistance between U3 pin 1 and pin 2 on 
the LCD module.  The resistance should be less than 1 
ohm.  If not, the cable is either bad or installed backwards. 
 
[  ] Resistance from U3-pin 1 to LCD pin 2 is less than 1 
ohm. 
 
[  ] Adjust VR1 to mid-position. 
 
[  ] Apply power to the T238. 
 
[  ] After about 1 second you should see the opening 
banners displayed on the LCD module.  If you do not see 
them or they look dim or overly dark, adjust VR1, the LCD 
contrast adjustment.  Fine tune VR1 for best viewing.  If 
text is not visible, check the soldering on U3 and J7 as well 
as the LCD cable and the header on the LCD module. 
 
[  ] LCD showing legible text. 
 
During the power up sequence, you will get a message 
saying that there is a 1-wire bus error.  If the error says no 
devices are present, you are OK.  If it says the bus is 
shorted to ground, then check U3, J6, D2, D3, R11, L2, 
and J2 for assembly problems or bad solder joints.   
 
Do not select any menu options at this time. 
 
[  ] Received error message saying no devices on the bus. 

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 ...

Page 10: ......

Page 11: ......

Page 12: ......

Reviews: