[linux-dvb] Lost lock problems over extended periods of time

Manu Abraham manu at kromtek.com
Thu Jun 9 15:54:06 CEST 2005

Johannes Stezenbach wrote:
> On Thu, Jun 09, 2005 at 12:21:16AM +0100, Andrew de Quincey wrote:
>>>So to summarise my current findings:
>>>*) Setting the tone every 60 seconds does not help.
>>>*) Setting the tone when the lock is lost causes it to be regained in under
>>>*) If you don't set the tone/reg0x08 on lock loss, you will never regain
>>>the lock.
>>>*) The contents of register 0x08 of the stv0299 stay constant.
>>>*) It cannot be noise/traffic on the i2c bus changing other registers since
>>>the only thing needed to fix the issue is to set register 0x08 again.
>>>*) No i2c traffic to the stv0299 besides reading the lock status occurs
>>>after the initial tuning attempt.
>>>*) Only a few cards are affected. Cards tuned to the same channels on other
>>>sites are fine. Cards using the same multiswitch at the same site are fine.
>>>*) At a site with the issue, channels can be manually reassigned between
>>>cards/machines until a stable situation is found. This is very time
>>>consuming though.
>>>*) Temperature is unlikely to be a cause.
>>>*) This problem occurs across a whole range of stv0299 based cards (we have
>>>several vintages of them from the last few years).
>>>*) There is no pattern temporally to the lock loss.
>>>*) The problem occurs across different multiswitches by different
>>>*) The signal is perfect (BER==0) up until the time the lock is lost.
>>>*) The problem _may_ affect stv0299 based Twinhan cards as well, but this
>>>needs verified.
>>Another one:
>>*) It is not interference from other DVB cards in the same machine - the 
>>machine I am testing stuff on only has one DVB-S card in it (and it doesn't 
>>have any DVB-T cards in it either).
> Maybe some dried up electrolytic capacitor making it
> senstive to small power drop outs, like in:
> http://defiant.wavecon.de/~alex/dvbbug/dvbbug.html

If manufacturers would shift to (the more expensive) tantulum 
capacitors, then that would be of no problem i believe..

But the problem was seen on new cards as well. Electrolytic capacitors < 
than a year old, rarely dry up, but no one can say for sure how old the 
capacitor has been there with the manufacturer. :-(


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