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 Post subject: Using digital content on old TV sets?
PostPosted: Jul Thu 23, 2020 10:33 pm 
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Ok folks,

This set turned out really well. The picture is awesome.

I'd like to be able to use dvd's or Netflix on my old TV sets to watch old programs. I have the necessary converters to do so but on this set I'm having audio issues. HDMI=RCA=Coaxial to tv. When I'm using a standalone digital converter box programming is excellent. Audio and video are great. When I use these converters I get a great picture but the audio is a buzz factory and I hardly get any audio gain. I have another old set. Like a 69 Magnavox that's all tube on solid state type motherboard and it seems to handle this signal, but this zenith is having nothing to do with it. I realize you get noise on menu's and subtitles but I'm not getting the audio during programming. Is it a impedance issue?

I'm using an old PS3... :roll:

What do you guys use for streaming content to your sets. I'd like the best quality possible.

Any ideas?

Thx.


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 1:13 am 
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You could have a look at this post:

viewtopic.php?f=3&t=332446&hilit=Playing+DVDs+on+vintage+TVs

I designed this device specifically to solve the problems you are having. You'll have to build it, PCB and kit of parts available from Silicon Chip magazine....

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 2:13 am 
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Cheap consumer RF modulators are sometimes buzz factories....I use Blonder Tongue agile modulators because they don't buzz when set up properly and you can transmit with them (which when you have a lot of vintage TVs saves you from making spaghetti monsters, or dragging signal boxes around).


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 2:59 am 
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Oh my gosh. I was hoping for an easier option. I will only be using one set at a time.

Is their anything I can purchase that's already assembled?

Will this work?

Or will I still have audio issues?

https://www.amazon.com/gp/product/B0096 ... 0DER&psc=1

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 3:13 am 
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Some of us choose to bypass the set's audio IF and detector completely, and add an RCA jack to the top end of the volume control. However, the Zeniths that used a 6BN6 or similar audio detector don't have a separate first audio stage so whatever device you use has to have a couple volts output to get good audio level. On most other sets that's not an issue.

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 3:21 am 
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The problem is you need to process the video signal prior to the modulator so that peak whites do not punch holes in the carrier. You might find that using a modulator in an old VCR and passing your signals through it (this is called E to E) works better, the VCR's electronics often includes circuitry to do this.

Another problem you will have is signals in the VBI that weren't there when the TV was designed. You need to strip these out. As well as diagonal white dashes in your picture they mess up the sound.

A higher sound carrier than most commercial modulators provide also helps.

If there is enough interest I could get some of these boxes made up, aligned for EIA rather than CCIR standards and make them available for sale.

Doing direct audio injection is sometimes possible but rarely trivial. Live chassis series string heater sets are out for this option for safety reasons.

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 3:01 pm 
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irob2345 wrote:
The problem is you need to process the video signal prior to the modulator so that peak whites do not punch holes in the carrier.

Another problem you will have is signals in the VBI that weren't there when the TV was designed. You need to strip these out. As well as diagonal white dashes in your picture they mess up the sound.

I think that the XDIMAX's primary use is stripping out the anti-copy effects sometimes added to the video sources as well as the extra signals in the VBI (Video Blanking Interval). It MAY do what you want, but it may not. You would insert it between the HDMI convertor and the RCA modulator. Kind of pricey.

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Fri 24, 2020 9:25 pm 
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gsxrkid74 wrote:
Oh my gosh. I was hoping for an easier option. I will only be using one set at a time.

Is their anything I can purchase that's already assembled?

Will this work?

Or will I still have audio issues?

https://www.amazon.com/gp/product/B0096 ... 0DER&psc=1

Blonder Tongue modulators are pre-assembled and do the same thing as the modulator you have only the Blonder Tongue modulators do it to cable TV broadcast quality, have a few more adjustments and sometimes need lytics changed if you buy the cheap used ones on eBay. If you don't want to transmit get an AM40 or BAVMz series Blonder Tongue and turn the output down till it's comparable to your current modulator. Those still have enough power to transmit if output is maxed, your antenna is optimised and you don't need more than a 100' range, but not whole block strong like an AM60.


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 6:24 am 
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I'm all for the blonder tongue transmitter for the long run as I plan on adding more tv's over time. I see what you mean on Ebay. They range from $60 to $500. What's the difference between the
AP60-550A and the AP60-550B?

So, funny thing. I was at a thrift shop and came across this GE AV modulator factory sealed for 3 bucks. I thought what are the chances? Sure enough it works. Audio and video are vastly improved. No more buzzing.

One thing I do have and both of my vintage tv's do it are these small specks that run vertically across the screen. They seem to slowly work they way horizontally up the screen in sections. If that makes since. About a year ago when I went through my first tube set it drove me nuts. I thought it was noise in the power line. Nope. It has something to do with interference. I've tried to shut everything off in my house. Nothing seems to effect it that manner but I have noticed it seems to be better at night. I don't know. I thought maybe a transformer or power lines behind my house could be causing it.

It does this regardless if its the direct feed from the modulator or my digital converter box. Its like the tuner is picking it up regardless.

Is it possible the blonder tongue would elevate this symptom. Any ideas what causes this?

Thanks peeps.... :D
.


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 8:13 am 
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I know EXACTLY what's causing it!

You have a power supply with a badly-designed flyback converter - somewhere!

See if you can improve the integrity of the shielding on the antenna connections. Use a proper balun to connect the co-ax to the 300 ohm terminals.
If that doesn't fix it, see if you can find an old-school copper-and-iron transformer based power supply to replace the noisy one.

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 4:27 pm 
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irob2345 wrote:
I know EXACTLY what's causing it!

You have a power supply with a badly-designed flyback converter - somewhere!

See if you can improve the integrity of the shielding on the antenna connections. Use a proper balun to connect the co-ax to the 300 ohm terminals.
If that doesn't fix it, see if you can find an old-school copper-and-iron transformer based power supply to replace the noisy one.


All of my vintage sets share the exact same symptom. I even have a few solid state Crt's that do the same thing. Replacing the coax from the modulator with higher quality (shielded) cable seemed to give me an improvement. I think?

Maybe getting a higher quality balun?

Hmmmm.....

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 6:59 pm 
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irob2345 wrote:

If there is enough interest I could get some of these boxes made up, aligned for EIA rather than CCIR standards and make them available for sale.


I'd be interested.


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 9:36 pm 
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It's not a copy protection issue. Those HDMI to composite converters don't generate Macrovision.

It could be caused by excessive video output level from the HDMI converter, low audio level, a bad RF modulator, or a misaligned IF. It could be a combination of all four. First, try feeding the composite signal into a modern TV to see if the problem is there. Next, try that modulator with a known good source such as a VCR or DVD.


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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Tue 28, 2020 11:06 pm 
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ac wrote:
It's not a copy protection issue. Those HDMI to composite converters don't generate Macrovision.

It could be caused by excessive video output level from the HDMI converter, low audio level, a bad RF modulator, or a misaligned IF. It could be a combination of all four. First, try feeding the composite signal into a modern TV to see if the problem is there. Next, try that modulator with a known good source such as a VCR or DVD.


Modern tv's don't do it. It's only an issue with any CRT I have. It does it regardless if its hooked up to a dvd/converter box or whatever. Even when I'm not using the HDMI converter. I have two tube type sets and two old solid state portables. They all share the same symptom. Like I said. It fluctuates. It's usually much better at nighttime.

So strange.

:roll:

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 Post subject: Re: Using digital content on old TV sets?
PostPosted: Jul Wed 29, 2020 2:20 am 
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Quote:
Modern tv's don't do it. It's only an issue with any CRT I have.

Is the common element that fact that the old TVs have 300 twin antenna connections and the newer ones have an F connector or similar?

The fact that a cable with better shielding improves things is a clue, we are heading in the right direction.

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