[mythtv-users] DVB-S locking problem

[Mark Carbonaro]

On 4 December 2011 07:09, Lawrence Rust <lvr at softsystem.co.uk> wrote:
> On Sat, 2011-12-03 at 20:07 +1100, Mark Carbonaro wrote:
>> Hi,
>>
>> I have a strange issue that started happening in the last month and
>> was wondering if anyone has some advice on how I can track down and
>> resolve the issue.
>>
>> I use a DVB-S (Tevii S660) which was working fine, but all of a sudden
>> it stopped getting a lock (Tl___).  I thought I may have blown the
>> tuner or something like that so I grabbed a PCI DVB-S tuner that I
>> had, but the same problem.  I connected my providers decoder back in
>> and it works fine (so the dish, cabling, LNB and smart card seem to be
>> fine).
>>
>> Thinking it may have been my Gentoo install I tried installing Arch
>> Linux (quicker than re-doing Gentoo from scratch), but the same
>> problem remained. In the end I reinstalled Gentoo from scratch, double
>> checked all the config, kernel etc, but still no locks.  I tried
>> running dvbscan and szap but again no transponders tuned and no locks.
>>
>> This is where it gets strange, if I stop mythbackend and power cycle
>> the S660 (its a USB external tuner) without rebooting the computer.  I
>> can run dvbscan and szap without issue.  dvbscan finds all the
>> channels and szap happily tunes and locks the channels.  If I then
>> start mythbackend, I can't lock channels and running dvscan/szap fails
>> until I power cycle the device.  Running a channel (scan all
>> transports) from mythtv-setup times out trying to tune all transports
>> regardless if I have power cycled the device or not.  It seems
>> everytime a mythtv component touches the tuner it kills it.
>>
>> I am running the following:
>> mythbackend version: fixes/0.24 [v0.24.1-101-g5da2367]
>> Linux Kernel Gentoo 3.0.6 (I have also tried running 2.6.39 kernel as
>> it seemed to stop working around the time I upgraded, but no luck)
>>
>> I would appreciate any help you are able to provide trying to figure
>> this one out as its got me stumped.
>
> I had a similar problem a while back with a tbs6981 dvb-s2 card.  With
> certain makes of LNB, sending a DiSEqC command burst would cause the LNB
> to lock-up.  The LNB then needed to be disconnected to be reset.  I
> found that if I disabled the DiSEqC message then all was OK.  In the end
> I bought a different make of LNB and that solved the problem.
>
> Maybe you have a DiSEqC switch or something that's misbehaving?  Or
> maybe you have Myth setup to use DiSEqC?
>
> --
> Lawrence
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Thanks for the reply,

I only have an LNB configured (no DiSEqC settings that I aware of and
nothing connected to the card), although when I was messing around
with dvbscan I noticed if I specified the LNB frequency (10700) it
would fail to tune, if the -l option was left out it would work after
a power cycle (again specifying it would cause the card to be "broken"
until a power cycle.  Not sure how it works when you don't specify he
frequency, I'm guessing there is some auto detection in dvbscan that
figures it out.

I used to have another LNB somewhere, I should see if I can find it
otherwise I buy another one and see if that will help.

Thanks,
Mark