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Discussion Starter · #1 ·
I've got a 42we655 Sony RPLCD. It has a built in QAM tuner. I've got just basic cable running directly into the cable coax input on the back of the set.


After wading through tons of scrambled digital channels. Many of them coming in as audio only I finally found what I was looking: for my local HDs.


So just as I'm getting totally happy about taking down my ugly OTA antenna the channel turns into blocks and my TV reads no signal. I think no big deal must just be the channel. Nope, none of the HD channels I just spent all that time looking for are coming in.


The weird thing is if I switch to a regular NTSC channel and then go immediately back the HD channels come in again. Even weirder is that this happens at exactly 12 minute intervals.


My questions are:


1.)Is there something wrong with my TVs QAM tuner.

2.)Does the cable company send out some kind of pulse to there digital boxes and when they do this it confuses my built in tuner.



Any ideas or advice appreciated. Thanks In Advance.
 

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Quote:
Originally Posted by DolfanJay
1.)Is there something wrong with my TVs QAM tuner.

2.)Does the cable company send out some kind of pulse to there digital boxes and when they do this it confuses my built in tuner.



Any ideas or advice appreciated. Thanks In Advance.
1) Probably


2) No
 

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Your HD channels' signal strength is probably on the border line of too weak. Unlike analog channels, digital channels can appear picture perfect one minute and totally black out in another if signal level is weak. Get a decent cable amp to see if you can get them stabelized or try eliminate a few splitters (each splitter causes 3.5+ db signal loss).
 

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Not saying this is what's happening ...


but ...


I've seen a few cases where the unencrypted QAM stations from the cable company were 'non-standard' or 'contained errors' (depending on how you look at it) to the point where they did not cause problems on the cable company's own boxes but did cause problems on some (but not all) QAM tuners. Some boxes are just more resiliant to certain problems than others.


Heck ... you even see it on OTA where a PSIP problem will cause issues with some (but not all) ATSC recievers.


And there's even a few cases where the cable companies have problems on their own boxes. For example, there's a certain combination of the Terayon CherryPicker (head end stat-muxer) and SciAtl 8300HD firmware that causes problems (on 8300HDs and no other boxes). Upgrade the CherryPicker or upgrade the 8300HD ... problem goes away.


Just saying it's a possibility. You could certainly have a bad QAM tuner or signal problems as mentioned above as well.


If your set has a diagnostic screen see if there's anything that hints at errors on the QAM channels.
 

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Discussion Starter · #5 ·
Thanks for all the responses.

Using dt-dc suggestion I checked my diagnostic and sure enough when it drops out the errors go from 0 up into the 250 range. Then about 15 seconds later they go back to 0. It was just coincidence switching back to a regular channel and coming back was just giving the signal time to come back to zero errors.


I tried it again today and watched an hour long program and I didnt have any problems with dropouts. Time Warner must have just been having problems with their signals or were doing work in the middle of the night.


So I guess I can be totally happy afterall:). Glad there was nothing wrong with my TV.



What is a good reading for my SNR and AGC readings? Also can I buy one of those amplified digital boosters and just add it directly to the line before it goes into the coax jack.
 

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Quote:
Originally Posted by DolfanJay
What is a good reading for my SNR and AGC readings? Also can I buy one of those amplified digital boosters and just add it directly to the line before it goes into the coax jack.
I like to see -10db to + 10db signal level (closer to 0 the better) and 35db or above (the higher the better) S/N ratio.


An amp increases signal strength but adds noise to the signal ... so ... don't add one unless it's needed.


Edit: Different boxes show different things in their diagnostic screens. Not sure where AGC should be.
 

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Quote:
Originally Posted by DolfanJay
My diagnostic SNR bounces between 17-19 db. The AGC hangs around 22%.
That is OOB (Out of Band Status); it is a bit low. That is for Analog, IIRC.


You need to look at In-Band Status for Digital and HD, it is the next line down.
 
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