[mythtv-users] HDPVR intermittent failure
Greg
gregl at nycap.rr.com
Sun Jun 28 16:31:45 UTC 2020
On 6/27/20 9:46 PM, DryHeat122 . wrote:
> On Mon, May 11, 2020 at 12:59 PM DryHeat122 . <dryheat122 at gmail.com
> <mailto:dryheat122 at gmail.com>> wrote:
>
> On Mon, May 11, 2020 at 2:41 AM Stephen Worthington
> <stephen_agent at jsw.gen.nz <mailto: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
> <mailto: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.
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>
> 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?
>
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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.
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