[mythtv-users] HDPVR intermittent failure

glen glenb at glenb.net
Sun Jun 28 02:50:21 UTC 2020 

On Sat, 2020-06-27 at 18:46 -0700, DryHeat122 . wrote:
> On Mon, May 11, 2020 at 12:59 PM DryHeat122 . <dryheat122 at gmail.com>
> wrote:
> > On Mon, May 11, 2020 at 2:41 AM Stephen Worthington <
> > stephen_agent at jsw.gen.nz> wrote:
> > > On Sun, 10 May 2020 20:20:30 -0700, you wrote:
> > > 
> > > 
> > > 
> > > >On Sun, May 10, 2020, 7:58 PM Greg <gregl at nycap.rr.com> wrote:
> > > 
> > > 
> > > 
> > > >Ok thanks I will investigate that.  But it's been working fine
> > > with the
> > > 
> > > >current power source for like a year now, and others on this
> > > list use it
> > > 
> > > >too.
> > > 
> > > 
> > > 
> > > USB cables often fit badly into the sockets.  If so, the
> > > connection
> > > 
> > > generally gets worse over time as you get dirt or oxidisation on
> > > the
> > > 
> > > contacts.  So badly fitting cables will degrade with time.  The
> > > result
> > > 
> > > is that the voltage drop across the cable will increase
> > > markedly.  And
> > > 
> > > they can be too thin - the amount of copper in the wires is too
> > > little
> > > 
> > > and that causes high resistance and a big voltage drop across the
> > > 
> > > length of the cable.  Some (most?) USB cables are designed only
> > > for
> > > 
> > > data transmission, or to run very low power devices.  For a high
> > > power
> > > 
> > > device, you need a better (thicker) cable.  The high power
> > > devices do
> > > 
> > > a negotiation with device supplying the power and request high
> > > power
> > > 
> > > mode.  If the cable is not capable of high power, that
> > > negotiation is
> > > 
> > > not supposed to work and the device should either only work in
> > > low
> > > 
> > > power mode or it should turn itself off.  But USB cable makers
> > > often
> > > 
> > > make cables not capable of high power transmission that will
> > > allow the
> > > 
> > > high power mode negotiation to succeed.  So even though the
> > > device
> > > 
> > > supplying the power is sending high current, the voltage drop in
> > > the
> > > 
> > > cable means that at the other end, the voltage can be below the
> > > level
> > > 
> > > required for proper operation or to fully charge the device's
> > > battery.
> > > 
> > > 
> > > 
> > > I have had two notably bad experiences with USB cables.  One was
> > > a USB
> > > 
> > > DVB-T tuner, and it was very like your experience - it would go
> > > for a
> > > 
> > > number of days just fine, then suddenly stop.  If I unplugged it
> > > and
> > > 
> > > plugged it in again, it would usually work again.  When I finally
> > > 
> > > investigated properly, I found the cable was just a little loose
> > > in
> > > 
> > > the PC's socket.  I replaced the cable with one that fit more
> > > tightly
> > > 
> > > and the tuner was much more reliable.  It still occasionally
> > > caused
> > > 
> > > trouble, but only when I had bumped the cables (or in one case,
> > > after
> > > 
> > > we had a small earthquake).  So because of that and because I
> > > needed
> > > 
> > > more DVB-T tuners, I finally replaced all my DVB-T tuners with an
> > > 8
> > > 
> > > tuner PCIe card.
> > > 
> > > 
> > > 
> > > The second bad experience was my Samsung Galaxy Tab S2 tablet. 
> > > Its
> > > 
> > > USB charging cable was supplied with it by Samsung, so I assumed
> > > it
> > > 
> > > was a good one.  But right from the start, the tablet took a long
> > > time
> > > 
> > > to charge, and the time gradually got longer and longer and the
> > > 
> > > battery life on one charge was getting less and less.  And then I
> > > 
> > > started to have to jiggle the cable in the socket to get it to
> > > charge
> > > 
> > > at all.  I actually called the Samsung help line about this, and
> > > they
> > > 
> > > said it sounds like a bad cable.  So I bought a expensive (NZ$30)
> > > 
> > > Pudney & Lee charging cable, which was a fair bit longer than the
> > > old
> > > 
> > > Samsung cable, but fit very tightly at both ends and was
> > > significantly
> > > 
> > > thicker - it has more copper in the wires in the cable.  Then
> > > suddenly
> > > 
> > > the battery charging times were what was specified for the
> > > tablet,
> > > 
> > > rather than three times as long.  And over a number of charging
> > > 
> > > cycles, the battery life came back again.  So the original
> > > Samsung
> > > 
> > > supplied cable was clearly bad from the start - it is probably
> > > less
> > > 
> > > than the specification required to charge the tablet properly as
> > > it is
> > > 
> > > too thin and has too much voltage drop even when the plugs fit
> > > 
> > > properly.  So definitely NZ$30 well spent.  But I am surprised
> > > that a
> > > 
> > > reputable company like Samsung would supply a bad cable with an
> > > 
> > > expensive top-of-the-line product like my tablet.  But they did -
> > > so
> > > 
> > > now I always suspect any USB cable I get and keep an eye on how
> > > well
> > > 
> > > it is working.
> > > 
> > > _______________________________________________
> > > 
> > > mythtv-users mailing list
> > > 
> > > mythtv-users at mythtv.org
> > > 
> > > http://email.mg.glenb.net/c/eJxNTksKwyAUPE3cVUz8xYWLbnoP9fkSQW2JttDb15ZCC8PA_GDABnQgBUkW_BwAdHCDvDcoEA3AEkAtqJjUUQkZGTIaXIl5EmzLsXpaYye7ZU4aBdzgvJqVz2vEgCYGoYFr7g0j2e693yZ-npbLQE6tN1qefe8Pej22YRWXcnH1G6aK17f5aZzuLR6NHPZfjge__QuyVkHw
> > > 
> > > http://email.mg.glenb.net/c/eJxFjTsOwjAQRE8Td1h2_AkpXNBQwRki27tOLJwAyQbE7bFEgTR6xeiNBlxMHoxm2UGQEaCLviKEPumUeoA2gm2TFaZDqw2KJHj0M5ZGi7HgEviCxCZnlfe9DTrFVKVOGZQymADyCMIogay4iejRqFPTnmve-Zb5_KGJXvy-jrW5-lzyMg6XvNGAlJ87EiFb3c867BuuW339j77f2j4X
> > > 
> > > MythTV Forums: http://email.mg.glenb.net/c/eJxFjMsKwyAUBb8m7ipGrzFZuOim_6H3kRTyKMYU-vcVuigMB4YDQxElkQf1jJR7JAqY2uQ8CYhMRBZpsDIYH3gAz0aMxrTx2oGZV96z3rmqJbKMoycnCMxICV2eOEBolm0PTtQal1pfZ-funX005CjXprdPXepbH2VWJf7kdp1czpb_f1_9hDZF
> > 
> > Thanks for all the suggestions.  I will investigate all of them. 
> > Something I do not see in here is an opinion that some software
> > problem could have evolved.  I was kind of thinking of that as a
> > possibility given that it worked fine for so long then seems to be
> > degrading.  OTOH I never thought of the possibility that the USB
> > connection could be degrading.  I'm going to try Greg's connector,
> > assuming I can get parts during the Apocalypse.  Also, his link
> > specifies Radio Shack parts.  What's Radio Shack?!? ;-)
> 
> Well folks this is getting frustrating.  I addressed a possible
> ventilation issue.  I also unplugged the power cord I had from the
> Myth box USB and connected it to an old iPad charger rated at 5V/2A. 
> No help.  It wouldn't record anything, no matter how much rebooting
> and power-cycling.  So I concluded the HDPVR was hosed and got a new
> one (more accurately, a replacement circuit board for it).  Powered
> it with the same wall wart.  Recorded great for a day.  Just turned
> it on and I have failed recordings and it won't respond when I try to
> manually play a channel.  Reboot, and it works fine, same pattern as
> before.  
> 
> I finally got a molex connector and am still going to try what Greg
> suggested, but I really don't think it's a power issue.  Apply makes
> good electronics and that wart has the same specs as the power supply
> that comes with the HDPVR.  The HDPCR isn't overheating.  It's not
> the HDPVR itself.  That only leaves the software on the myth box. 
> Anyone have ideas how to troubleshoot that?
> 
> 
> _______________________________________________mythtv-users mailing 
> listmythtv-users at mythtv.org
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have you tried a conf file in /etc/modprobe.d setting this option:
options ir-kbd-i2c enable_hdpvr=1


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