After wasting several hours that I didn‘t have available to waste trying unsuccessfully several times to do a channel scan on my Vizio VT420M LCD TV, I finally found a fix (suggested by Vizio) that worked for me. Since I am apparently not the first person to encounter these problems and almost certainly won’t be the last, I decided to post my experience here in case others run into the same problems. My situation applies to the VT420M but apparently applies to other Vizio models as well.
Since my cable company (Comcast) is doing considerable channel realignment in my area, I decided to do a channel scan for only the second time since getting my unit last summer. The first problem I encountered was that Vizio said in the “Channel Scan” instructions that the process should only take a few minutes. That is very misleading since depending upon the number of channels involved, it can take much longer than a “few minutes”, as you will see below.
With the input set to “cable”, I started my channel scan. My first hint that something seemed wrong was after 30 minutes when only 55 digital channels had been found and zero analog channels (the progress meter was only about half way across at that point). I felt that there should have been more channels found by this amount of time, particularly since a similar scan I had just completed on my Magnavox H2160MW9 DVD recorder took only 12 minutes to complete. 15 minutes later (about 45 minutes into the process), nothing had changed. The progress meter was in the same position and no additional channels had been found (when the Vizio TV finds a channel it displays the channel number…and sub-channel number if appropriate..along with the signal strength).
At that point, I decided to terminate the scan and verify that that the coax was connected properly and that I was getting a strong signal. After verifying both, I re-started the scan. This time, after 30 minutes NO channels had been found (digital or analog) and the progress meter was stalled about half way across again. I terminated the scan a second time, powered the TV off and back on then did a scan of channels using “antenna” as the input instead of cable. This process found a few channels as expected and took about 3 minutes to complete.
I then tried for the third time to scan using “cable” as input to see if the previous “antenna scan” or unit power off had helped and once again, it had found no channels after 30 minutes (and the progress indicator stalled yet again). After doing some research on the internet, I found that Vizio had two recommended procedures to use if problems doing channel scans were encountered http://www.tvtechnology.com/article/83808
I tried the first procedure, the double re-scan which means disconnecting the coax input then doing a complete channel scan on the “cable” input with the coax disconnected. After that completes, re-connect the coax and do the scan on “cable” input a second time with the coax remaining connected this time. The first scan, with the coax disconnected took about 5 minutes. After re-connecting the coax, I tried the scan the second time. This time everything worked fine for me. The TV started finding both digital and analog channels within a minute or two. The entire scan took 49 minutes and found 408 digital and 52 analog channels. The number and types of channels others find will vary depending upon the user's local cable company.
Had that procedure not worked for me or had I lost the scanned channels after powering off the unit (as described in the referenced article but which didn’t happen to me, at least not yet….knock wood….), Vizio’s second recommended procedure is a tuner hard reset. That entails disconnecting the coax input *and* the power cord then holding down the “power on” button on the TV for 30 seconds while reconnecting the coax and the power cord. After doing that, attempt the channel scan on the “cable” input once more and it should work.
Fortunately, I didn’t have to use the second procedure (the tuner hard reset procedure). Also, that procedure seems difficult for one person to do. The “power on” button is on the opposite side of the screen as the coax input so it seems it would be difficult to hold down the “power on” button, reconnect the coax and the power cord ALL AT THE SAME TIME! That sounds like a two person job.
Also, Vizio didn’t make it clear but they probably meant to reconnect the coax cable first *THEN* connect the power cord! I’ve been raised to believe that you never connect coax or any other type of cables to a unit with the power already on or it can possibly cause a component failure somewhere along the line.