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Old 9-Jun-2017, 11:16 PM   #1
BigBean
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No Signal

'alo again.

Thankee for all the help in enabling us to cut the cord!

Unfortunately, we hit a common snag: Tuner troubles.

Earlier this week after a storm we cannot get our 40+ stations; none. SO I tested the power and concluded correctly or not that the thing had been fludged. Now, after going atop our roof and refitting with a new RCA TVPRAMP1R booster, we still cannot receive a digital signal. Connections are confirmed and proper and the antenna seems untouched.

However, I double-checked the power plug in the basement. QUITE hot and don't believe this is normal. The outlet checked out fine earlier; however I just tried another outlet to no avail. The dongle where the coax connects remains cool.

SO … I'm probably looking at a fludged HDTV tuner, YET that hot power plug ( transformer, really ) makes me wonder what's going on outside.

On the telly I noticed in the Sony's diagnostics menu that NTSC is selected, this Bravia is one of the earlier HDTV's dating from 2008. It is grayed out, I can only access this menu when a signal is detected.

The last thing I did was reset the TV to factory settings per the manual.

What next? Thanks in advance, gang!

Last edited by BigBean; 9-Jun-2017 at 11:42 PM.
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Old 10-Jun-2017, 3:19 AM   #2
rabbit73
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Hello, Big Bean

Sorry to hear you are having trouble. You should be able to go into the menu even if there are no signals and select air/antenna in the Channel Menu and do a scan for channels.

What model number is the TV?

It is possible that the tuner or the preamp got zapped by the storm.

You will need to find out which part of the system isn't working by substituting known good parts for each; TV, preamp, antenna, coax.

The power transformer does get quite warm during normal operation, but the dongle/power inserter doesn't.

Your previous thread:

http://forum.tvfool.com/showthread.php?t=14856

Your previous tvfool report is no longer on the server.
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Last edited by rabbit73; 10-Jun-2017 at 3:30 AM.
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Old 10-Jun-2017, 12:15 PM   #3
BigBean
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'morning, Rabbit, thanks for the interest.

The first thing we did was rescan following the outage. We got into the habit of rescanning 46 times a year the first year since new channels keep coming.

Looked at the antenna following installing the new pre-amp; didn't seem damaged. I just assumed that when they're hit they'll show some obvious scorching. Nope. Yes, I suspect the coax could be fried as well, that's not going to be easy.

No "easy" way to test a bad tuner in the TV itself? It's a Bravia KDL 40S4100.

Thanks.
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Old 10-Jun-2017, 1:22 PM   #4
Jake V
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Quote:
Originally Posted by BigBean View Post
No "easy" way to test a bad tuner in the TV itself? It's a Bravia KDL 40S4100.
Easiest way is to swap in another television, if one is handy.
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Old 10-Jun-2017, 1:56 PM   #5
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Exactly, Jake. Naturally we only have the one.
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Old 11-Jun-2017, 1:17 AM   #6
rabbit73
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Quote:
However, I double-checked the power plug in the basement. QUITE hot and don't believe this is normal.
If the transformer gets hotter than usual, it might be caused by a short in the coax. Do you know how to use a voltmeter and an ohmmeter?
Quote:
No "easy" way to test a bad tuner in the TV itself? It's a Bravia KDL 40S4100.
Thanks for the model number.
manual
https://docs.sony.com/release/kdl40s4100.pdf

If you get the TV working, it has a Signal Diagnostics screen in the channel menu that will help with antenna testing.

Can you borrow a TV to test with your antenna?

If you have a old VCR, you can use it as a signal source when playing a tape to test the TV tuner. Most of them have a channel 3 or 4 output that can be connected to your Bravia tuner.

You can buy an external tuner like the Channel Master 7003 that has channel 3 or 4 output. If it shows that your tuner is bad, you can connect the tuner composite A/V, component, or HDMI output to the TV input.
https://www.channelmaster.com/Digita..._p/cm-7003.htm

http://www.solidsignal.com/pview.asp?p=cm-7003

http://www.avsforum.com/forum/186-co...erter-box.html
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Last edited by rabbit73; 11-Jun-2017 at 1:26 AM.
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Old 11-Jun-2017, 8:54 PM   #7
BigBean
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Thanks, Rabbit.

Voltmeter, generally yes. I assume I need both ends access to test, and realize the inner wire is both pos and neg. So I'm looking at a resistance equal or near that to the rating, which I assume is 75Ω. I kinda thought the plug hot for its purpose too. That's gonna be a real drag to replace if you're right, but cheaper than a TV!

I cannot use the Diagnostics Menu as it can't find a signal to analyze. It's there, but looking for a signal that won't come.

YES! we do have an old VCR. So, I hook that up, but how can I conclude the health of the built-in TV Tuner if it's looking for a digital signal? Interesting, as VCRs are analog.
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Old 11-Jun-2017, 9:23 PM   #8
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You would use the ohmmeter to check for opens or shorts in the coax when it is not connected at either end. Don't make resistance measurements with the ohmmeter with any voltage on the coax; you will zap the meter.
Quote:
So I'm looking at a resistance equal or near that to the rating, which I assume is 75Ω.
No, that is the impedance of the coax for RF signals. The ohmmeter measures DC resistance, which would only be a few ohms for continuity of the center conductor from one end to the other. It would also be a few ohms for continuity of the shield from one end to the other.

If you don't have access to both ends near the meter when checking for continuity, short the far end and check between the center conductor and the shield and the end by the meter. It should be a few ohms. The test current makes a round trip out the center conductor, through the short at the far end, and then back to the meter on the shield.

To check for shorts in the coax, neither end should be connected. Make a resistance check between the center conductor and the shield at either end. It should be an open circuit, with no continuity.

Do the resistance measurements first. If the coax is OK, then do the voltage measurements.

When you make voltage measurements, start at the power inserter without the coax to the preamp connected. Measure the voltage at the connector that goes to the preamp between the center and the shield threads being careful not to short the voltage. I usually stick a short length of 18 gauge solid copper wire in the connector for the voltmeter probe.

Then connect to coax to the power inserter and check the voltage at the end of the coax that connects to the preamp. Again, be careful not to short the shield to the center conductor. I usually insert an F-81 adapter on the end of the coax and then insert a short length of 18 gauge solid copper wire as with the power iinserter.
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Last edited by rabbit73; 11-Jun-2017 at 9:49 PM.
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Old 11-Jun-2017, 9:41 PM   #9
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Quote:
I assume I need both ends access to test,
No, you need to make voltage measurements at the end opposite the power inserter.

Quote:
and realize the inner wire is both pos and neg.
No. usually, the inner wire is positive and the shield (outer) is the negative (aka "ground" or "low" side. Just be aware that there are F-connectors out there with a clear coating on the exterior that forces one to put the negative meter lead on the inside (threads) of the F-connector while simultaneously probing the center conductor with the positive meter lead and, not shorting them together...

Quote:
and realize the inner wire is both pos and neg.
Nope. One cannot measure the impedance of coax cable with a simple multimeter. All you can do is measure the resistance of continuity of both the shield and the center conductor and also check to verify they are not shorted to each other.

An analog VCR can check only the analog portion of a tuner, some of which is shared by the digital signal path. If it fails to receive analog signals, it's bad, but the opposite cannot be assumed.
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Old 12-Jun-2017, 1:33 AM   #10
BigBean
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Cool

Now you guys know why I ask questions.

I think the reasonable approach is to connect that VCR first, that's the easiest. As with most chickens, I'm loathe to walk the roof yet again. UGH.

DUMB QUESTION: What analogue signals? I thought they were all phased out. I did save my report, could that have ideas?

As always, I'll report back once I get results. Patience, it may take over a week. I'm still traumatized by reinstalling a new pre-amp!

Thanks, all!
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Old 12-Jun-2017, 3:38 AM   #11
rabbit73
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Measuring RCA TVPRAMP1R Preamp Voltage





The 18 gauge wire is the same size as the center conductor of RG6 coax. Actually, the piece of wire in the photos came from a short length of RG6 coax.

The meter switch was set to the 0-50 VDC range.

This measurement is called measuring the output voltage without a load, because the preamp is not connected.

When the preamp is connected, the voltage will drop to its normal operating level, called voltage under load.
Attached Images
File Type: jpg RCAPreampVoltage1.jpg (159.6 KB, 699 views)
File Type: jpg RCAPreampVoltage2.jpg (154.7 KB, 693 views)
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Last edited by rabbit73; 13-Jun-2017 at 4:04 PM.
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Old 12-Jun-2017, 3:58 AM   #12
rabbit73
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DUMB QUESTION: What analogue signals?
Not a dumb question; it's an intelligent question.

You need a signal source to test your TV tuner. You don't have any digital signals to test the tuner.

Your tuner will receive analog and digital signals.

Most VCRs will put out an RF analog signal when playing a tape.

There are usually two RF coax connectors on a VCR. One connector is for RF IN for antenna or cable.

The other RF connector is for RF OUT that goes to the TV tuner at the antenna IN connector of the TV.

The VCR acts like a little TV transmitter, and can usually be set to send an analog TV signal on channel 3 or 4.

OK?
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Old 12-Jun-2017, 11:58 AM   #13
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What analogue signals? I thought they were all phased out
Actually, not all. Only the full power stations were required to transition to digital. Low power and translators were not required to do so and there are still analog TV stations on the air in various parts of the country.

Good luck. Let us know what you find or if you have additional questions.
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Old 15-Jun-2017, 3:58 AM   #14
rabbit73
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Pete Higgins measured the RCA preamp voltages and current when he did his excellent reviews of the preamp.
http://forum.tvfool.com/showthread.php?p=49017

http://www.highdefforum.com/local-hd...amplifier.html



It is a little more difficult to measure the voltage under load, because you need access to the center conductor when the preamp is connected. This is one way to do it:



Method #2 is easier if you have a T-Adapter:



Measuring the current:

Attached Images
File Type: jpg RCAPreampVload1.jpg (214.4 KB, 682 views)
File Type: jpg RCA TVPRAMP1R Voltage.jpg (72.3 KB, 696 views)
File Type: jpg RCAPreampVload2.jpg (196.5 KB, 642 views)
File Type: jpg RCAPreampCurrent.jpg (191.2 KB, 638 views)
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Last edited by rabbit73; 15-Jun-2017 at 8:38 PM.
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Old 16-Jun-2017, 8:11 PM   #15
BigBean
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Wink

SOLVED. But you guys are going to be very, very angry at me.

So: I was right initially, the first pre-amp had been zapped during the storm.

What went wrong afterwards? A very simple stupid mistake: I had the power inserter facing the wrong direction in the connection. A real Homer moment. Where it says right on the inserter, "To Antenna", it means that direction. Boy, oh boy. The good news is dummy does not have to go up on the roof again for a while.

Another thing: Surge protection is your friend. Frankly, I've long thought of getting one for the house. Some of those in-wall units don't make it.

Thanks all and please consider making this a stickey 'cuz there's gold herein.
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Old 17-Jun-2017, 12:34 AM   #16
rabbit73
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Thanks for the report. We're not angry, we're glad you found out what was wrong. We learned from your mistake, too.

Yup, that's what it says.



When you turn it around, it sends the amp voltage to your TV, which survived.

Attached Images
File Type: jpg RCAPreampTOANT.jpg (147.4 KB, 618 views)
File Type: jpg Power_Inserter_for_Amp.jpg (143.2 KB, 634 views)
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Last edited by rabbit73; 17-Jun-2017 at 12:50 AM.
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Old 17-Jun-2017, 3:23 AM   #17
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I had the power inserter facing the wrong direction in the connection. A real Homer moment.
Been there, done that.....
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Old 17-Jun-2017, 3:12 PM   #18
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Y'know, the freakin' thing is, I usually check the obvious first and this time I failed utterly. It does explain things though. It could be why the transformer was overheating; the power had nowhere to go!

Now, follow me for a sec. One thing I've always tried to use to teach myself electricity is to think of it as a river. Now, when testing components such as coax, I get stuck on the terminology: Capping, shorting, terminating a component all the same thing is tantamount to attaching an alligator clip to one end, biting the copper wire ( the "conductor" ) while touching the negative ( here, the threading ) so it effectively creates a circuit once the multimeter is connected at the opposite end, so one can test that component?
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Old 17-Jun-2017, 3:20 PM   #19
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It could be why the transformer was overheating; the power had nowhere to go!
The transformer was overheating because (too much) power was going where it wasn't supposed to.
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Old 18-Jun-2017, 7:22 PM   #20
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Quote:
Originally Posted by BigBean View Post
Now, follow me for a sec. One thing I've always tried to use to teach myself electricity is to think of it as a river. Now, when testing components such as coax, I get stuck on the terminology: Capping, shorting, terminating a component all the same thing is tantamount to attaching an alligator clip to one end, biting the copper wire ( the "conductor" ) while touching the negative ( here, the threading ) so it effectively creates a circuit once the multimeter is connected at the opposite end, so one can test that component?
Making a water analogy is often useful when following current flow in a circuit. Your description of a test sounds like my Step 5 when testing coax with an ohmmeter when the far end of the coax isn't near the meter. DO NOT make any resistance measurements when there is voltage on the coax. Here are all the steps:













Attached Images
File Type: jpg TestingCoax1.jpg (198.3 KB, 573 views)
File Type: jpg TestingCoax2.jpg (196.2 KB, 619 views)
File Type: jpg TestingCoax3.jpg (201.7 KB, 600 views)
File Type: jpg TestingCoax4.jpg (193.0 KB, 572 views)
File Type: jpg TestingCoax5.jpg (215.4 KB, 540 views)
File Type: jpg TestingCoaxTip1.jpg (140.3 KB, 579 views)
File Type: jpg TestingCoaxTip2.jpg (135.2 KB, 575 views)
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Last edited by rabbit73; 18-Jun-2017 at 7:29 PM.
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