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There are several problems in a satellite system that can present themselves that can be difficult to diagnose. Among them are impedance mismatch and insufficient LNB voltage. In this document I will cover simple methods to diagnose and correct the following problems:
-Impedance mismatch
-Short circuit
-Open circuit
-Incorrect STB output voltage
-Low voltage at LNB
-STB excessive current
To perform all these tests you will need the following equipment:
- Digital multimeter (DMM). Current rating of 750 mA.
- 75 ohm resistor
- (2) barrel connectors
- Short length of cable with F-connectors attached
- Short length of cable with F-connector on one end, stripped on the other
- (2) paperclips
Impedance mismatch
Description: Impedance mismatch is where the cable and/or a component has an impedance (resistance) outside the normal range of 75 ohms. DISHTV's Zenega Cd 1004iS is particularly sensitive to impedance mismatch. Symptoms can include †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message, missing transponders, low signal/quality and unresponsive switches.
Cause: Almost always caused by sharp bends, crimps in cables, bad cable ends.
Testing
You will need a 75 ohm resistor and digital multimeter to test for impedance mismatch. A 75 ohm terminator cap will work in place of the resistor.
1. Disconnect the cable to be tested from the satellite system.
2. Measure and record the actual resistance of the 75 ohm resistor or terminator that you will be using for the test.
3. Hook the resistor/cap between the copper center conductor and the ground/shielding on one end of the cable. On the other end of the cable measure resistance between the center conductor and cable ground/shielding. Resistance should be the value you measured in step #2, +/- 10%. If the measured value is at all outside the acceptable range, replace cable and/or ends to correct.
Short Circuit
Description: A short circuit is when the cable or another component has a direct connection between the conductor and ground. Symptoms can include †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message, STB/IRD rebooting, and damaged switches/STB/IRD.
Cause: Bends, crushed cable, improperly made cable ends, bad component such as a switch, staple thru cable.
Testing
You will need a digital multimeter to test for short circuit.
1. Disconnect the cable/component to be tested from the satellite system.
2. Set digital multimeter to continuity testing mode. Ensure the meter is working by touching the probes together, the meter should beep.
3. Check for continuity on one end of the cable by touching one probe to the center conductor and the other to cable ground/shielding. A beep indicates a short in the cable/component being tested. If continuity is detected replace the component/cable/cable ends.
Open circuit
Description: An open circuit is where there is a break in the current path. This can be either on the conductor or ground or both. Symptoms are †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚ÂÂ, no signal or quality.
Cause: Bends, bad component, bad cable ends, cable/component not hooked up.
Testing
You will need a digital multimeter and a paperclip for this test.
1. Disconnect the cable/component to be tested from the satellite system.
2. Set digital multimeter to continuity testing mode. Ensure the meter is working by touching the probes together, the meter should beep.
3. Attach paperclip to one end of the cable/component to be tested by hooking across the center conductor to the ground/shielding.
4. Check for continuity at the other end of the cable/component by touching one probe to the center conductor and the other to cable ground/shielding. If there is no continuity the cable component has an open in either the conductor or ground/shielding. Check and replace cable ends, cable or component as necessary.
Incorrect STB/IRD output voltage
Description: Incorrect output voltage is where the STB/IRD does not put out sufficient voltage or puts out too much voltage when the STB/IRD is calling for 13V (vertical/RHCP) or 18V (horizontal/LHCP). Symptoms can include missing all 13V or 18V transponders or both, sudden shutdown or reboot or IRD/STB, damage to switches and/or LNB, intermittent reception of transponders.
Special notes on voltages: DishPro and DP Plus LNBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s output both polarities as 19V horizontal polarity signal. For testing FTA STB be sure that antenna settings are in standard rather than dishpro configuration when testing.
Cause: Incorrect voltage at the IRD/STB is an indication of failure within the tuner/LNB output portion of the IRD/STB. Check fuse if no output voltage at all.
Testing
You will need a digital multimeter and a short piece of cable for this test.
1. Attach cable to LNB input on IRD/STB.
2. Power on IRD/STB and go to antenna settings. Select a satellite and transponder.
3. Check DC voltage between the center conductor of the cable and the ground/shielding. Flip thru several transponders taking readings. Every other transponder should be 13V/18V. Acceptable range for 13 volt transponders is 12VDC-14VDC, 17VDC-19VDC for 18 volt transponders.
Low voltage at the switch/LNB
Description: Low voltage at the LNB/switch is where insufficient voltage is reaching the LNB/switch. Symptoms can include missing RHCP transponders or missing both RHCP & LHCP, STB/IRD rebooting or shutdown, unreliable switching, and †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message.
Cause: Can be several causes including insufficient output voltage at the LNB, impedance mismatch, excess cable length, too many inserted devices/splices in the line.
Testing
You will need a digital multimeter for this test.
1. Disconnect cable from LNB/switch at the end of the cable run.
2. Power on IRD/STB and go to antenna settings. Select a satellite and transponder.
3. Check DC voltage between the center conductor of the cable and the ground/shielding. Flip thru several transponders taking readings. Every other transponder should be 13V/18V. Acceptable range for 13 volt transponders is 12VDC-14VDC, 17VDC-19VDC for 18 volt transponders.
If voltage is low for either 13V or both 13 & 18V transponders perform STB/IRD voltage test and impedance test of the cable and components. If no voltage is present check for open circuit. Solution will vary according to cause.
STB/IRD excessive current
Description: Excess current drain can be caused by low voltages, power hungry components such as DP34 & DP Plus LNBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s or damaged components. Check the maximum current rating of your IRD/STB, it is normally stamped on the back of the unit near the LNB input.
Testing
You will need a digital multimeter, a piece of stranded copper wire, (2) barrel connectors, (2) paperclips, and a short length of cable with F-connectors on it.
1. Hook one end of short cable to the STB/IRD. Attach barrel connector to other end of cable.
2. Attach a barrel connector to the cable from your LNB/switch setup.
3. Attach the copper wire between the ground on both the short cable and the cable leading to the LNB. Do not connect the center conductor.
4. Insert paperclip in the center of each barrel connector.
5. Place multimeter in current measuring mode. Attach probes to the center conductors of both cables by attaching to the paperclips in step #4.
6. Power up IRD/STB. Go into antenna settings and switch between the satellites you are using and different transponders on these satellites, noting the current indicated on the multimeter. Compare with maximum current rating for your STB/IRD. Note that numbers approaching but not exceeding maximum are indicators of a problem. The maximum output current of the STB/IRD is not necessarily the sustainable current output, which typically is lower. Also note that DP34 switches, DP Plus LNB and other components have high current requirements that some STBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s cannot handle. Long cable runs, impedance mismatch and defective components can also cause excess current consumption.
-Impedance mismatch
-Short circuit
-Open circuit
-Incorrect STB output voltage
-Low voltage at LNB
-STB excessive current
To perform all these tests you will need the following equipment:
- Digital multimeter (DMM). Current rating of 750 mA.
- 75 ohm resistor
- (2) barrel connectors
- Short length of cable with F-connectors attached
- Short length of cable with F-connector on one end, stripped on the other
- (2) paperclips
Impedance mismatch
Description: Impedance mismatch is where the cable and/or a component has an impedance (resistance) outside the normal range of 75 ohms. DISHTV's Zenega Cd 1004iS is particularly sensitive to impedance mismatch. Symptoms can include †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message, missing transponders, low signal/quality and unresponsive switches.
Cause: Almost always caused by sharp bends, crimps in cables, bad cable ends.
Testing
You will need a 75 ohm resistor and digital multimeter to test for impedance mismatch. A 75 ohm terminator cap will work in place of the resistor.
1. Disconnect the cable to be tested from the satellite system.
2. Measure and record the actual resistance of the 75 ohm resistor or terminator that you will be using for the test.
3. Hook the resistor/cap between the copper center conductor and the ground/shielding on one end of the cable. On the other end of the cable measure resistance between the center conductor and cable ground/shielding. Resistance should be the value you measured in step #2, +/- 10%. If the measured value is at all outside the acceptable range, replace cable and/or ends to correct.
Short Circuit
Description: A short circuit is when the cable or another component has a direct connection between the conductor and ground. Symptoms can include †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message, STB/IRD rebooting, and damaged switches/STB/IRD.
Cause: Bends, crushed cable, improperly made cable ends, bad component such as a switch, staple thru cable.
Testing
You will need a digital multimeter to test for short circuit.
1. Disconnect the cable/component to be tested from the satellite system.
2. Set digital multimeter to continuity testing mode. Ensure the meter is working by touching the probes together, the meter should beep.
3. Check for continuity on one end of the cable by touching one probe to the center conductor and the other to cable ground/shielding. A beep indicates a short in the cable/component being tested. If continuity is detected replace the component/cable/cable ends.
Open circuit
Description: An open circuit is where there is a break in the current path. This can be either on the conductor or ground or both. Symptoms are †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚ÂÂ, no signal or quality.
Cause: Bends, bad component, bad cable ends, cable/component not hooked up.
Testing
You will need a digital multimeter and a paperclip for this test.
1. Disconnect the cable/component to be tested from the satellite system.
2. Set digital multimeter to continuity testing mode. Ensure the meter is working by touching the probes together, the meter should beep.
3. Attach paperclip to one end of the cable/component to be tested by hooking across the center conductor to the ground/shielding.
4. Check for continuity at the other end of the cable/component by touching one probe to the center conductor and the other to cable ground/shielding. If there is no continuity the cable component has an open in either the conductor or ground/shielding. Check and replace cable ends, cable or component as necessary.
Incorrect STB/IRD output voltage
Description: Incorrect output voltage is where the STB/IRD does not put out sufficient voltage or puts out too much voltage when the STB/IRD is calling for 13V (vertical/RHCP) or 18V (horizontal/LHCP). Symptoms can include missing all 13V or 18V transponders or both, sudden shutdown or reboot or IRD/STB, damage to switches and/or LNB, intermittent reception of transponders.
Special notes on voltages: DishPro and DP Plus LNBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s output both polarities as 19V horizontal polarity signal. For testing FTA STB be sure that antenna settings are in standard rather than dishpro configuration when testing.
Cause: Incorrect voltage at the IRD/STB is an indication of failure within the tuner/LNB output portion of the IRD/STB. Check fuse if no output voltage at all.
Testing
You will need a digital multimeter and a short piece of cable for this test.
1. Attach cable to LNB input on IRD/STB.
2. Power on IRD/STB and go to antenna settings. Select a satellite and transponder.
3. Check DC voltage between the center conductor of the cable and the ground/shielding. Flip thru several transponders taking readings. Every other transponder should be 13V/18V. Acceptable range for 13 volt transponders is 12VDC-14VDC, 17VDC-19VDC for 18 volt transponders.
Low voltage at the switch/LNB
Description: Low voltage at the LNB/switch is where insufficient voltage is reaching the LNB/switch. Symptoms can include missing RHCP transponders or missing both RHCP & LHCP, STB/IRD rebooting or shutdown, unreliable switching, and †œsearching for satellite signalÃƒÂ¢Ã¢â€šà ¬Ã‚Â message.
Cause: Can be several causes including insufficient output voltage at the LNB, impedance mismatch, excess cable length, too many inserted devices/splices in the line.
Testing
You will need a digital multimeter for this test.
1. Disconnect cable from LNB/switch at the end of the cable run.
2. Power on IRD/STB and go to antenna settings. Select a satellite and transponder.
3. Check DC voltage between the center conductor of the cable and the ground/shielding. Flip thru several transponders taking readings. Every other transponder should be 13V/18V. Acceptable range for 13 volt transponders is 12VDC-14VDC, 17VDC-19VDC for 18 volt transponders.
If voltage is low for either 13V or both 13 & 18V transponders perform STB/IRD voltage test and impedance test of the cable and components. If no voltage is present check for open circuit. Solution will vary according to cause.
STB/IRD excessive current
Description: Excess current drain can be caused by low voltages, power hungry components such as DP34 & DP Plus LNBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s or damaged components. Check the maximum current rating of your IRD/STB, it is normally stamped on the back of the unit near the LNB input.
Testing
You will need a digital multimeter, a piece of stranded copper wire, (2) barrel connectors, (2) paperclips, and a short length of cable with F-connectors on it.
1. Hook one end of short cable to the STB/IRD. Attach barrel connector to other end of cable.
2. Attach a barrel connector to the cable from your LNB/switch setup.
3. Attach the copper wire between the ground on both the short cable and the cable leading to the LNB. Do not connect the center conductor.
4. Insert paperclip in the center of each barrel connector.
5. Place multimeter in current measuring mode. Attach probes to the center conductors of both cables by attaching to the paperclips in step #4.
6. Power up IRD/STB. Go into antenna settings and switch between the satellites you are using and different transponders on these satellites, noting the current indicated on the multimeter. Compare with maximum current rating for your STB/IRD. Note that numbers approaching but not exceeding maximum are indicators of a problem. The maximum output current of the STB/IRD is not necessarily the sustainable current output, which typically is lower. Also note that DP34 switches, DP Plus LNB and other components have high current requirements that some STBââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s cannot handle. Long cable runs, impedance mismatch and defective components can also cause excess current consumption.