[mythtv-users] Black screen, audio, green snow

Gary Buhrmaster gary.buhrmaster at gmail.com
Thu Oct 6 16:58:50 UTC 2016

On Thu, Oct 6, 2016 at 2:48 PM, Ian Evans <dheianevans at gmail.com> wrote:

>> > On Oct 6, 2016, at 10:39 AM, Ian Evans <dheianevans at gmail.com> wrote:
>> >
>> > I first thought this might be related to the HDHomerun power warts, but
>> > that issue usually resulted in pixellation.

First, RF is hard.  Really hard.  No one is likely
to have the tools available to do a proper diagnostic
tests.  So, what you get are WAGs.  Here is another.

The impact of high ripple has resulted in enough various
reports over the years (unable to tune, unable to
establish/maintain ethernet, random drop-outs,
drop-outs only when two tuners are in use, etc.)
that whenever something "different" happens, and
especially if one is using one of the (original) HDHR
power warts (known to have a limited lifetime), I
usually recommend having a replacement on cold
standby to test with(*).

> Just double checked. Both incidents happened on the same channel. It's a
> flamethrower of a signal but maybe they're having some other issue.

Suspicious, of course.  Note that the HDHR's can
actually have issues with too strong of a signal
(their tuners/demods, because of the price/design
point, are nowhere near as good as most vendors
in the TV manufacturing business).  Sometimes
you might even need to point an antenna in a
slightly offset direction to reduce the power (if all
channels are high power, a simple pad may work).

And new construction (or even new vegetation
(I hear trees happen, especially this time of year))
can result in new and interesting multipath signals
that can cause issues.  Weather can also impact
signal (moving vegetation).

Also note that every gen HDHR tuner/demod gets better
(the silicon gets better), and there was a firmware
update a few years ago (early 2013?) to deal with a
particular issue where there was dropouts for one of
the generation of devices.  You should likely update
your firmware if you have not done so recently.

There is also a more obscure issue (of which I only
have a vague recollection) that on some (I do not
recall if it was the 2nd or 3rd gen) devices a
particular choice by the TV station engineer to leave
one of the ports unconnected in one of their RF
transmitter path one ended up with random dropouts.
This typically happened only with specific channels
(and might start to happen after an upgrade to the
transmitter by the station).  Apparently the issues
were never seen with real TV's (see the comments
above about TV tuner/demods being better), so
it is next to impossible to get a station engineer to
fix what ain't broke.

(*) FD: I proactively replace most consumer electronics wall
warts with higher quality switching supplies from one of the
respected vendors (locally sourced from the new surplus
stores).  I really hate dealing with diagnosing power
related "glitches".

More information about the mythtv-users mailing list