FT 2-3 Lesson 6 Troubleshooting Digi TV Service
For proper operation, what is the specified channel input range to most digital STBs?
-15 to +15 dBmV
Where is a problem that originates during capture and processing of a DTV channel mostly likely to be observed?
Can be observed throughout the network
Identify the problem
Customer calls to say their DTV reception is intermittent
Analyze the problem
Gather more detail about the problem
Diagnose the symptoms
Measure signals
Amp levels: For proper operation, -15 to +15 dBmV is the specified QAM channel input range to most STBs. T/F?`
True
Magnitude of problem to its description: Network-wide
A problem that originates during capture and processing
Magnitude of problem to its description: One fiber-node or a specific neighborhood
A problem that originates in the distribution network
Magnitude of problem to its description: Isolated to one customer
A problem that originates in the drop system
How much do you know about successful troubleshooting?
Able to utilize a variety of tools and test equipment Persistent and attentive to detail Confidentaly execute corrective action(s) to fix a problem
Which of the six troubleshooting steps can likely be combined and performed at the same time or performed out-of-sequence?
Although troubleshooting is a problem-solving technique that follows a systematic process of analysis, isolation, and diagnostics, these three steps can often be combined and performed at the same time or performed out-of-sequence
Why does troubleshooting of digital TV (DTV) service logically revolve around the digital set-top box (STB)?
Because the digital STB functions as a gateway, providing DTV service to customer's TV and other services, it is logical that troubleshooting of DTV service revolves around the STB
Verify the solution
Check DTV reception with the customer
When replacing a splitter to resolve a digital TV (DTV) service problem, what does confirming the splitter output levels before attaching the output connectors do?
Confirmation reinforces the technician's confidence that the problem will be resolved by replacing the splitter.
What prevents authorization of some digital STBs and ordering of video-on-demand (VOD) content?
DTV services, such as VOD and authorization of some STBs, require communications with the headend through the RF return path
During which step of the six-step troubleshooting process for a digital TV (DTV) service problem are quadrature amplitude modulation (QAM) channel measurements typically taken?
Diagnosing symptoms.
Isolate the elements
Eliminate sections of the network as possible causes of the problem
Which of the following is data in an out-of-band data channel? Choose all that apply
Emergency alert system (EAS) STB authorization STB application Electronic program guide (EPG)
What is added during modulation to QAM channels that enable DTV receivers to detect and repair data that is lost or corrupted during transport?
FEC
Amp levels: Digital STBs add forward error correction (FEC) data to the modulated channel to ensure reliable reception. T/F
False
Amp levels: QAM channels amplitude should be relative to analog TV channels, which is typically 6 dB lower than the amplitude of the analog TV channels. T/F?
False
What is included in digital STBs to provide product engineers with information pertaining to the STB operation and the channels coming into and leaving the STB?
From the beginning, digital STB has included diagnostic screens to provide the product engineers with information about the STB operation and the channels coming into and leaving the STB
After a digital TV (DTV) service problem has been analyzed and possible causes considered, what is accomplished by isolating the various network elements?
It narrows the scope of likely problem sources.
How are the functions of a digital set-top box (STB) like those of a personal computer (PC)?
Many of the functions of a digital STB are like those of a PC with memory for boot-up software, an operating system (OS), graphical interfaces, middleware, and applications software
What is done to ensure equal power in all channels in a network with analog and digital modulation channels?
Operate the analog TV channels at higher amplitude level than the QAM channels.
What are the CAS (conditional access system) elements? Choose four areas
Out of band modulator (OOB) STB Headend STB controller Subscriber management system (SMS)
What are some set-top box (STB)-related troubleshooting calls that can be avoided with customer education?
Overheating STB Blocked IR detector VOD recordings
What will you use to diagnose a digital television (DTV) issue?
Receipt of STB Auth data: Set-top box (STB) diagnostic All QAM channel parameters: Digital signal analyzer of an SLM Receipt of intact EMMs: STB diagnostic Return channel frequency and power level: STB diagnostic QAM channel that the STB is tuned: STB diagnostic QAM measurements in the field: Digital analyzer of an SLM
Resolve the problem
Replace the suspected component
When troubleshooting a digital TV (DTV) authorization issue, what can be verified using the set-top box (STB) diagnostic page?
STB reception of authorization message data.
Which type of set-top box (STB) operates more like Data Over Cable Service Interface Specification (DOCSIS) cable modems with return channels on the same frequencies used for cable modems?
STB with DOCSIS Set-top Gateway (DSG) client software and embedded DOCSIS modems.
Which of the following characterizes the successful troubleshooter?
Someone with an inquisitive and relentless desire to solve and fix problems (could be someone that is pleasant, organized, and patient)
What does a set-top box (STB) diagnostic page of a quadrature amplitude modulation (QAM) channel showing signal-to-noise ratio (SNR) near or below 30 dB indicate?
The QAM channel quality is on the edge for reliable reception, and the source of the problem is likely in the distribution network or customer premises.
How much do you know about return path connectivity?
The _______ (STB diagnostic) can be used to verify STB connectivity with the headend The _______ (STB controller in the headend) instructs the STB to adjust its return channel amplitude levels. An output level that is at, or near, maximum from the STB can indicate _______ (excessive loss in the drop system)
When troubleshooting a problem, what can be revealed by asking the customer open-ended questions?
The customer may reveal that the problem began after some seemingly unrelated work was done inside or outside the premises by other service providers or people that unintentionally damaged the cable
What digital set-top box (STB) element sometimes causes the customer to take self-education of the STB features, capabilities, and limitations for granted?
The customer-friendly electronic program guide (EPG) user interface of digital STBs can cause the customer to take self-education of the STB features, capabilities, and limitations for granted
Which of the following digital TV (DTV) trouble calls could have been avoided with customer education about the product?
The digital set-top box (STB) overheats.
During the isolation step of troubleshooting, what method is typically effective?
The divide-and-conquer method (or half-split) is typically employed effectively during the isolation step of troubleshooting
What must a technician be aware of when analyzing a digital TV (DTV) problem?
There is frequently more than one contributor to a specific DTV service problem
Amp levels: Although it rarely happens, input amplitude levels to a STB that are too high could be problematic as levels that are too low. If this happens, the best solution is to check the cabling throughout the premises for a customer-installed amplifier. T/F?
True
Amp levels: Because the data used for modulation error ratio (MER) and bit error ratio (BER) are added during modulation, impairments on channels having good MER and BER readings occur before modulation. T/F?
True
Amp levels: When viewed on a spectrum analyzer, a quadrature amplitude modulation (QAM) channel resembles a haystack. T/F?
True
