Periodic "Invalid Format" on LG LCD with 50' BJC Run - AVS Forum
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post #1 of 10 Old 03-25-2010, 06:37 AM - Thread Starter
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I have a 20" LG LCD TV in the kitchen, and a 50' run of Blue Jeans Series 1 Beldon cable to my DirecTV box in the other room.

Usually, this setup works just fine. However, periodically, I get the "Invalid Format" message on the TV and the audio and video go away. Wiggling the cable at the DirecTV box will usually resolve the problem.

I've tried using "port protectors" (the little 6" more flexible extenders) on the ends, thinking perhaps the really thick BJC cable is causing the connectors not to mesh properly. No help there.

Ideas? The cable run was not easy to make, and therefore I don't really want to do it again, and I really don't want to invest in another cable either. The connectors look just fine, and I made sure they were protected while I was running the cable.

Thanks,
Jeff
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post #2 of 10 Old 03-25-2010, 07:27 AM
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Just to be clear: When you say "wiggling the cable at the DirecTV box will usually solve the problem," is that the HDMI cable, or something else?

It sounds like a handshake issue. That could be (though may well not be) the result of the long cable run, as some devices don't tolerate capacitance on the DDC line well, and that's where the handshake happens--all long cables will, unfortunately, have high capacitance and so even if you did go to the trouble to replace the cable there's no real guarantee that it would fix anything. And, of course, if it's a handshake issue it could equally well have nothing at all to do with the cable run and could be a problem in the DDC circuitry either in the source or in the TV.

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post #3 of 10 Old 03-25-2010, 09:28 AM - Thread Starter
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Kurt, thanks for the quick response.

Yes, sorry for not being clearer. It is the HDMI connector at the source side that I have to muck with to get it working again. And it's always the connector on the main cable. Whether it is plugged directly into the DTV unit, or into a port protector. It's never a problem on the display side. I've changed the source unit to a different model, same issue. I have not tried changing the display.

I just forced the source unit to 720p only, in case the issue is related to higher 1080i resolutions. Not sure if that would be a factor here.

When it works (which is most of the time) the video and audio are great. So I think you are spot on with the handshake. On average, I probably have to mess with the connection once a week. Some weeks never, sometimes two or three times a day.

Would contact cleaner help? Would a booster (which I understand actually goes on the display end) help?

Jeff
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post #4 of 10 Old 03-25-2010, 09:40 AM
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Usually recommend one of these to help your issue:

port-saver - you tried, but seems to not have helped

hd ez lock - supports your cable from your chassis, takes off stress, keeps cable firm

this is a problem with HDMI connection in general, and DTV/Cable/Tivo boxes seem especially sensitive...could be that the internal traces are stressed/cracked from the strain of a heavy HDMI cable. Internal damage is fairly common.

Here's a link on the tivo community forum about this problem (in this case though damage was caused by the tivo being pushed against the wall)

(edited to add tivo link)
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post #5 of 10 Old 03-25-2010, 10:02 AM
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Quote:
Originally Posted by chumbley View Post

It is the HDMI connector at the source side that I have to muck with to get it working again.

Yeah, it definitely sounds handshake-related. When you wiggle the cable you're probably just breaking the connection for a moment, and then it reinitializes. It's quite possible that a power down/power up would do the same; if it does, that would indicate that the problem is not with the physical connection integrity but is strictly electronic. If it doesn't, I'd suspect a possible intermittent connection inside the connector.

If the problem is an intermittency in the connector, it's very likely that immobilizing the connector-to-portsaver joint when it's working well (I might try binding it up in a few windings of gaffer's tape) and keeping the connection from getting moved will fix the problem.

Quote:
Originally Posted by chumbley View Post

I just forced the source unit to 720p only, in case the issue is related to higher 1080i resolutions. Not sure if that would be a factor here.

It could be, if your projector for some reason is finicky when handling 1080i. The bitrate for the signal itself is the same, but if for some reason it were going funky when the source changes resolutions, that would fix it. Equally, if the projector for some reason has trouble with 720p, fixing the resolution to 1080i might fix things.

Quote:
Originally Posted by chumbley View Post

Would contact cleaner help? Would a booster (which I understand actually goes on the display end) help?

Contact cleaner's unlikely, but certainly could not hurt anything, so it's pretty much a nothing-to-be-lost-but-time solution. A booster isn't going to help; well, I should qualify that. A conventional booster just boosts signal level on the data pairs, and that won't help at all because the handshake is on the DDC. However, it is possible that a booster that tries to rehabilitate a degraded DDC signal might help. Markertek sells one from Gefen: http://www.markertek.com/Routers-Switchers-DA's/HDMI-Repeaters-DAs/Gefen-Inc/EXT-HDMI1-3-141S.xhtml?GEF-141SBP
Not cheap, unfortunately. There may be a cheaper one out there somewhere, but you'd definitely need to be sure it is designed to fix DDC problems--if it doesn't say so, it isn't.

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post #6 of 10 Old 03-25-2010, 10:28 AM - Thread Starter
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Ok, thanks for the ideas and feedback.

The connection in question is in a very protected area (inside a cabinet where nothing else is stored), so I'm pretty sure it isn't being moved (at least in a normal bumping the cable kind of way). I can try taping it up. Having changed the source unit, the port savers, and tried it with and without port savers, the common factor is always the source end of the Series 1 cable. I can validate that next time by pulling the display end, and see if that allows the handshake to succeed, but I know I've tried messing with that end before (it is much easier to get to) and it hasn't helped.

I know we've lost the signal right in the middle of a show, so that sort of rules out changing resolutions being the issue.

I'll try resetting one end or the other next time, and see if that changes anything. I've probably already tried that - but don't remember. I've been living with this for quite some time. Not sure if it is starting to happen more often, or we are just getting less tolerant of the issue!

Thanks for the tip on the Geffen booster. While I'd rather not spend that much money, I'd be willing to IF it fixed the problem. It isn't that much more than an identical replacement cable - and definately easier to install.

My concern is, that all logic points to an intermittent connection on the source end of the Series 1 cable. And other than replacing the cable (cost and time), I'm not sure I can do anything about that...

Jeff
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post #7 of 10 Old 03-25-2010, 10:33 AM
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Alternatively--and this is a tad risky--if it is an intermittency inside the connector it could be that giving the cable a fairly good hard tweak in one direction, and holding it there (tape, again, being probably the best tool) might tension the connection together. The downside is that which way to tweak would be a guess, and if you're wrong it's possible it could just permanently break the intermittent connection.

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post #8 of 10 Old 03-25-2010, 12:38 PM - Thread Starter
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Hmm. Interesting idea. I'll try the contact cleaner first. Less destructive!

Jeff
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post #9 of 10 Old 03-27-2010, 06:16 AM - Thread Starter
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Update: Nothing I tried (locking on 720p, forcing handshake by resetting devices and unplugging display end cable) worked.

I attempted to put some tension on the connection between the source end of the series 1 cable and the port saver plug, by doubling the port saver cable back to the series 1 cable. I didn't tweak or force it. However, the end of the series 1 cable came out of the rubber jacket. More evidence that this was the problem all along.

I was able to get the pins back into the end, and got it working again. For now. I'm sure it won't last long. Looks like new cable time. Argh.
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post #10 of 10 Old 03-27-2010, 09:31 AM
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Chumbley: I've just sent you a PM....

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