[mythtv-users] HDPVR intermittent failure

DryHeat122 . dryheat122 at gmail.com
Sun Jun 28 16:46:31 UTC 2020


On Sun, Jun 28, 2020 at 9:32 AM Greg <gregl at nycap.rr.com> wrote:

>
> On 6/27/20 9:46 PM, 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://lists.mythtv.org/mailman/listinfo/mythtv-users
>>> http://wiki.mythtv.org/Mailing_List_etiquette
>>> MythTV Forums: https://forum.mythtv.org
>>
>>
>> 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.orghttp://lists.mythtv.org/mailman/listinfo/mythtv-usershttp://wiki.mythtv.org/Mailing_List_etiquette
> MythTV Forums: https://forum.mythtv.org
>
>  The next time it won't record,try to cat it and see if it responds.  This
> is the command I use,  cat /dev/video0 > test .. dmesg for the proper port
> it's connected to. This may help too see if it is the software or not..
>
> I am curious were you got the motherboard? There used to be a place in
> Ohio (I believe) ,but they have gone out of business.
>
I will give that a try.  The circuit board I got some time ago and I think
it was on ebay.
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