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Gary Evans

Intermittent Loss Of Video Signal

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This one has me stumped. Any ideas would be appreciated.

Range Video 900MHz 500mW audio/video transmitter system/3 cell LiPo/Deans ultra plug power connection to a JST plug on the Rx end.

I have been chasing an intermittent loss of video signal and finally found that I could sometimes reproduce the effect by moving the wires between the battery and Tx. I replaced both Deans plug connectors (real Deans not substitutes) and checked the wires between the connector and JST connector that plugs into the Tx for continuity with a test light.

No change. When touching/moving the wires loses the signal the wire at the JST connector is not being moved. Just touching the wires between the battery and Dean connector will do it. Touching the Tx case does nothing and I have tried several different batteries.

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That might be a bad contact in the battery pack. I've already had an unsoldered cell tab once, it would also open the contact randomly.

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That might be a bad contact in the battery pack. I've already had an unsoldered cell tab once, it would also open the contact randomly.

I've tried 3 differant batteries with the same result. Sometimes it works fine and then sometime it becomes intermittent. I was just trying it again on the bench, the video signal would stop and I could bring it back just by putting my finger close (1/4 inch) to the the wires on either side of the Deans connector.

Edited by Gary Evans

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If a human body's proximity to the Tx, or its wiring, causes it to do odd things then it sounds like the Tx or video camera is defective. When the video signal goes away, does it come back when you move things around with a long wood stick?

Also, if this is a very intermittent thing, then maybe it is just strong multipathing interference at the test bench's environment. Do things improve if you operate the system outdoors, away from structures?

How about posting some photos of your TX setup? Maybe we will see something of interest in how it is all put together.

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It does the same thing inside or outside and touching the wires or Deans connector with a wood yardstick produces the same result. Here are some pictures. I had been wrapping the camera to Tx lead around the pan servo and thought that may be the problem so as you can see in the last picture I tried looping the excess lead right behnd the camera. No change!

http://tinyurl.com/3cowo4

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... touching the wires or Deans connector with a wood yardstick produces the same result.

That sort of suggests that the problem is a "mechanical" issue; hidden broken wire, bad solder joint, defective connector, etc.

Here is a simple test. Get everything running then force the failure. Wait another 15 minutes while it is failed. Is the Tx's case temperature cool to the touch or is it hot like normal? If cool, then you are missing voltage to the Tx during the failure period.

BTW, what CCD camera are you using? If it is a KX-131, then keep in mind that a 5VDC Voltage Regulator is required. Without that, the camera will become a fancy paperweight in a jiffy.

I replaced both Deans plug connectors (real Deans not substitutes)

FWIW, the expensive Deans connectors are a bit bulky for this low current app (they are great for 50A motors :) ). A small JST BEC connector would be just dandy for A/V power.

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That sort of suggests that the problem is a "mechanical" issue; hidden broken wire, bad solder joint, defective connector, etc.

Here is a simple test. Get everything running then force the failure. Wait another 15 minutes while it is failed. Is the Tx's case temperature cool to the touch or is it hot like normal? If cool, then you are missing voltage to the Tx during the failure period.

BTW, what CCD camera are you using? If it is a KX-131, then keep in mind that a 5VDC Voltage Regulator is required. Without that, the camera will become a fancy paperweight in a jiffy.

FWIW, the expensive Deans connectors are a bit bulky for this low current app (they are great for 50A motors :) ). A small JST BEC connector would be just dandy for A/V power.

The Tx case does stay hot when the video signal is lost so I think I'm down to replacing it. The camera is a 12v KX 151. I use Deans on all of my batteries so they will be interchangeable. They are big but easier to attach than JST's as I don't have a crimper.

Thanks for the replies on this thread. Appreciated!

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At this point I would suspect the problem is related to the video signal or the camera itself. It would be wise to carefully inspect that signal path for trouble. Plus, try another camera or use any other external video source for the test.

If you have a mic on the Tx, can you still hear audio when the video goes away? If audio also goes away, then something evil inside the Tx is suspected.

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At this point I would suspect the problem is related to the video signal or the camera itself. It would be wise to carefully inspect that signal path for trouble. Plus, try another camera or use any other external video source for the test.

If you have a mic on the Tx, can you still hear audio when the video goes away? If audio also goes away, then something evil inside the Tx is suspected.

The mic is another story. The specs on the Rx indicate that audio is line level but the mic it came with appears to be unamplified (two wire). When I recently bought a recorder I realized that the mic wasn't working. The only thing it will transmit even slightly is scratching on the mic surface but no other sounds. I bought a RS 3 wire mic but it produced the same results so I suspected something in either the Tx or Rx.

I think I'll just send the whole package back to Range for testing rather than guess and buy something that wasn't broken.

Thus far I've had a rather bad experience with the current lot of video equipment and trying to buy the best available didn't accomplish much. The Tx, camera and video goggles have been replaced once already. Bought a OSD that didn't work and my recorder lasted 60 days. Quality control has a lot of growing room.

Edited by Gary Evans

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The mic is another story. The specs on the Rx indicate that audio is line level but the mic it came with appears to be unamplified (two wire)

Well, you probably know the drill. There are about three basic flavors of electret (condenser) microphones.

(1) The common electret mic has just a basic FET amp in it that is employed to get the signal level from a few microvolts to a few millivolts. These are the types with two leads, but most three lead electrets are that way too. These would provide low sound levels on systems that need standard line level signals. However, some A/V Tx's have a preamp in them, as well as the necessary DC power bias to support a two lead mic. Maybe that is why your possibly defective A/V system has the two lead capsule on it?

(2) There are some electrets that have a little bit more gain, but they are still not line level. An A/V Tx that ordinarily needs "line level" audio signals would work with this if the Rx audio volume was set higher than usual and you just wanted to mostly hear the louder noises (like from a motor).

(3) Then there are true Line Level mics. These are designed to be used with audio gear that has inputs compatible with ~1V signal amplitudes. This type of mic is needed on many A/V Tx's if you expect to hear normal sound levels.

Long story short, your A/V equipment supplier should be able to offer the specifications for their Tx's audio signal and the mic that would work best with it. If they don't know, then run for the hills.

The only thing it will transmit even slightly is scratching on the mic surface but no other sounds.

The scratch test is good enough for this evaluation. Before you return the system, try this test. Frankly, I'm curious about what you will find.

Bought a OSD that didn't work

If you bought it from dpcav.com then I would definately want to help you get it going. Was it a Vizion or Inspire OSD (products that I can help you with)? Otherwise, maybe someone else can help you with the other brands of OSD (just post the details in the forum). Sometimes the needed fix is easier than sending the stuff back for repair. :)

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