I have been using Tablo DVRs for many years. Somewhere along the way my newest Tablo (Tablo Quad TQNS4B-02-CN) started pixelating at random times and would sometimes display the weak signal error when trying to tune a channel. In every case I proved that the signal was fine by connecting the antenna cable directly to the TV or to a USB tuner (Hauppauge). Many others have made this same observation. After many weeks of troubleshooting I decided to do some testing with my old Tablo (Tablo DVR SPVR4-01-NA), aka Tablo 4-Tuner, side-by-side to see if the pixelation occurred at the same time on both. My old Tablo is also a quad tuner.
I connected my antenna cable (via a splitter) to both of my Tablos and powered them up. I used my ATSC DigiAir Pro to measure the signal strength and SNR after the splitter. The readings were excellent. I logged into the “Old Tablo” using the Roku Ultra on my TV. I also logged into the “New Tablo” using Google Chrome on my laptop. (I clicked the red X first to clear all of the Tablo data from the browser.) At this point I am watching the same channel on two devices at the same time using two different Tablos (an old model and new model - both quads and both with hard drives attached). It took about 15 minutes of flipping through channels on both when suddenly, on a channel change, the “New Tablo” started pixelating. The “Old Tablo” continued to display perfectly on the TV!!!. Note that I had adjusted the timeline so that the two displays were in sync to make it easier to correlate any pixelation. This was an exciting find since it proved that the signal from the antenna was still working perfectly as shown on the “Old Tablo” but yet pixelation was visible on the “New Tablo”.
I decided to go one step further to rule out all other variables. I logged out of both Tablos (on the Roku and Chrome on the laptop) - cleared all the sync data - and logged back into the two Tablos in reverse. (The laptop now was displaying the “Old Tablo” and the TV via the Roku was displaying the “New Tablo”). Well, you guessed it - I observed the exact same behavior except reversed. The “New Tablo” (now on the TV) continued to show the pixelation problem and weak signal errors regardless of the device used to display the live TV content.
As an additional test I removed the hard drive from the “New Tablo” and re-ran all of my tests. The results were exactly the same as before - the “New Tablo” continued to display the Weak Signal error at times (when tuning to a new channel) and pixelate at random times. During these errors the “Old Tablo” had no issues at all! I also made sure that every setting was identical between the two Tablos. The only setting that was different was the Tablo Name field under General. The firmware version on each Tablo is the same (v2.2.30).
I also changed out the power supply on the new Tablo. Both power supplies that came with the Tablos are rated at 12V 2A. The DC plugs will not fit interchangeably between the two Tablos but I just happened to have in my junk box a 12V 5A (rated) power supply with a DC plug that fit perfectly. However, nothing changed with my testing results. The new Tablo still pixelated etc at the same time that the old Tablo ran fine.
This puts the final nail in the coffin. This pixelation and weak signal issue is DEFINITELY* a problem in the Tablo firmware or hardware in the Tablo Quad TQNS4B-02-CN. As a tech savvy observer (and engineer) this appears to be an AGC (Automatic Gain Control) issue with the tuner circuitry/firmware. The reason I am posting my experiences is due to the large number of similar complaints which seems to make this a systemic issue instead of an isolated failure with my particular Tablo Quad.
For now I am going to continue using my old Tablo and enjoy an error free Tablo experience. The New Tablo will be relegated to a shelf in the garage. I really wanted to use the new model with the internal hard drive installed.
UPDATE: I wonder if the tuners in the Quad versus the 4-Tuner are more susceptible to overload. My signal is quite strong here (as seen in the DigiAir photo - 85.4 dBuV.). I assumed (I know, I know) that the tuner circuitry/design would be the same but if the Quad is more sensitive to overload that may explain what I am seeing. If the designers adhere to the ATSC specification I would think that the overload threshold would be the same on the Tablo 4-Tuner versus the Quad. I am going to do some further testing with attenuators and let you know the results.
*Pixelation will still occur if the signal really is weak. The signal is strong for this test case.
Hope this helps someone,