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 Post subject: Predicta Debutante Pattern Generator Works DVD player doesnt
PostPosted: Aug Sun 08, 2021 1:00 am 
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Joined: Feb Thu 18, 2021 3:09 pm
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I'm working on an 11L43 chassis Predicta Debutante. Caps, resistors over 1meg, K networks replaced and tubes tested for shorts and emission. It seems to be working perfectly when I hook up my pattern generator but not coax from a DVD player. I even tried hooking up an RF modulator where I can set what channel to send the signal to and it's just static. Am I missing something here?

(I also know the vertical is squeezing towards the top and plan to fix that afterward. I have a vert lin pot I'm going to replace the fixed resistor that is there currently.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 2:41 am 
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Do you have another TV that works on NTSC TV signals? If so you could try that on your set up.
All the DVD players I've ever seen only output a video signal not a RF modulated signal.
The separate RF modulator should have worked however. Something else must of been wrong with that set up. What modulator did you use? Many simple ones just let you chose channel 3 or 4.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 2:48 am 
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Judging by the photos, the vertical problem may be foldover rather than linearity. Foldover will affect linearity but adjusting linearity won't help. Foldover can be caused by leaky capacitors in the vertical circuit (or leakage outside the capacitors). You could also try replacing the vertical tubes; a tube tester may not find this.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 3:08 am 
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Joined: Feb Thu 18, 2021 3:09 pm
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Notimetolooz wrote:
Do you have another TV that works on NTSC TV signals? If so you could try that on your set up.
All the DVD players I've ever seen only output a video signal not a RF modulated signal.
The separate RF modulator should have worked however. Something else must of been wrong with that set up. What modulator did you use? Many simple ones just let you chose channel 3 or 4.


Yes I need to troubleshoot more. I used a B&K 1211 as the pattern generator. the RF let me choose channel 3-4. My other digital RF lets me choose any channel for VHF or UHF and that didn't work either.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 3:10 am 
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Jim Mueller wrote:
Judging by the photos, the vertical problem may be foldover rather than linearity. Foldover will affect linearity but adjusting linearity won't help. Foldover can be caused by leaky capacitors in the vertical circuit (or leakage outside the capacitors). You could also try replacing the vertical tubes; a tube tester may not find this.


I need to check to make sure all the resistors in the vertical and damper section are correct. I don't like how the 11L43 doesn't have a schematic because there are a few resistors that are not the same as the 10L43


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 12:00 pm 
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How are you hooking the RF Modulator to the DVD Player? Red, White and Yellow jacks to Modulator, coax output and a matching transformer to the antenna terminals of the TV?

Maybe the modulator is bad, or the power supply to it, if it's external. The Modulator I use won't even switch on (red pilot light comes on) until it sees a signal from the DVD Player.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 1:32 pm 
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Eric H wrote:
How are you hooking the RF Modulator to the DVD Player? Red, White and Yellow jacks to Modulator, coax output and a matching transformer to the antenna terminals of the TV?

Maybe the modulator is bad, or the power supply to it, if it's external. The Modulator I use won't even switch on (red pilot light comes on) until it sees a signal from the DVD Player.


I've hooked the same hookup to another set and it's working fine. Let me try a completely different DVD player. Would it have to do anything with the alignment pots in the video amp section?


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 2:46 pm 
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Jackmach5 wrote:

Yes I need to troubleshoot more. I used a B&K 1211 as the pattern generator. the RF let me choose channel 3-4. My other digital RF lets me choose any channel for VHF or UHF and that didn't work either.

You need to be a bit clearer.
Do you mean that the 1211 let you select channel 3 or 4?
It gets a bit difficult to answer your questions when you are not using the right terms.
What do you mean by "digital RF"?
There are modulators that modulate using the Digital TV ATSC format. Those will work with a digital TV (flat screen) TV but won't put out the right RF signal for a vintage set.
You want to use a analog RF modulator, those vintage ones are usually made by Blonder-Tongue.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 2:54 pm 
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Jackmach5 wrote:
I've hooked the same hookup to another set and it's working fine. Let me try a completely different DVD player. Would it have to do anything with the alignment pots in the video amp section?

Here again, what you say is confusing.
Alignment involves adjusting RF coils in the tuner and IF strips.
There are no "alignment pots in the video amp section".
If the tuner doesn't tune to the modulator that would be a problem with alignment, but you had the TV receiving the channel when using the pattern generator so that is not the problem. That would point to a problem with the RF modulator you tried with the DVD player.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 3:31 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
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Notimetolooz wrote:
Jackmach5 wrote:

Yes I need to troubleshoot more. I used a B&K 1211 as the pattern generator. the RF let me choose channel 3-4. My other digital RF lets me choose any channel for VHF or UHF and that didn't work either.

You need to be a bit clearer.
Do you mean that the 1211 let you select channel 3 or 4?
It gets a bit difficult to answer your questions when you are not using the right terms.
What do you mean by "digital RF"?
There are modulators that modulate using the Digital TV ATSC format. Those will work with a digital TV (flat screen) TV but won't put out the right RF signal for a vintage set.
You want to use a analog RF modulator, those vintage ones are usually made by Blonder-Tongue.


I apologize, I didn't have the setup in front of me at the time. The B&K 1211 has settings that say Channel A, and Channel B. Channel A is where I get the perfect display and I have to tune into channel 7 on the tuner.

I hooked up my DVD player to a Digital Full Band Modulator through AV cables. Then coax out to the tuner and I couldn't get an image on any channel. I tried many different channels on the modulator and tuner.

I see you answered my question though, I didn't realize I need an analog RF modulator. I'll look into those. Thank you very much


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 3:52 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
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https://www.ebay.com/itm/363326908691?e ... SwSLlgU5g2

Would this be an appropriate RF modulator to get?


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 6:20 pm 
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Joined: Dec Mon 23, 2019 5:52 pm
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Those analog VHF tuners have a low band, channels 2 thru 6, and a high band, channels 7 thru 13. It's possible your low band isn't working if you're trying to get channels 3 or 4. Obviously, the high band that contains channel 7 is okay.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 8:07 pm 
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rcadanny wrote:
Those analog VHF tuners have a low band, channels 2 thru 6, and a high band, channels 7 thru 13. It's possible your low band isn't working if you're trying to get channels 3 or 4. Obviously, the high band that contains channel 7 is okay.


Ahh how would I go about troubleshooting that?


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 9:15 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
Something as simple as this would do to put the video signal from the DVD player onto analog RF.
https://www.amazon.com/GE-RF-Modulator- ... d=11042001
Similar units were made under the RCA brand name among others.
They have a switch to select channel 3 or 4.
The one on ebay is a fine unit, probably better quality but notice it has adjustments. How would you set it correctly if you didn't have a well adjusted working TV set?
Simpler is better here. VCRs do have a RF output that you could select channel 3 or 4, they used the same circuit that is in the separate modulator.
VCRs have other issues sometimes with very old TV sets.
The analog modulator are getting a bit harder to find because most people have digital TVs, that is why I asked what kind you had.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 11:11 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
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I have a Radioshack 15-2526 which works fine on my other vintage tube sets.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Sun 08, 2021 11:40 pm 
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Location: Redlands CA
Jackmach5 wrote:
https://www.ebay.com/itm/363326908691?epid=1600258765&hash=item5497f8a913:g:kC4AAOSwSLlgU5g2

Would this be an appropriate RF modulator to get?


You don't need anything that elaborate, as others have pointed out a simple Modulator will do. I dont know if you can still get them at local stores like Wal-Mart or Big Lots, but the majority of mine came from Thrift Stores.

I use this hooked to an older Blu ray player with analog outputs to run a 1958 RCA, the set wont produce a watchable picture at all using VHS as a source.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Mon 09, 2021 12:04 am 
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Joined: Feb Thu 18, 2021 3:09 pm
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Yeah VCRs never produce a correct image on any old set I have. That's why I've been troubleshooting with the DVD player. I'll keep messing around with the tuner and pattern generator. Hopefully I can come back with good news. I'm so close to this set working perfectly.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Mon 09, 2021 12:52 am 
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Location: Dallas, TX
Jackmach5 wrote:
I have a Radioshack 15-2526 which works fine on my other vintage tube sets.

OK, that should do the job.
It is possible that the Predicta's tuner can not fine tune enough. basically that means that the tuner may need to be aligned. Another possibility is that the RF amp circuit or the convertor circuit in the tuner isn't working right. Maybe the modulator doesn't put out as strong a signal as the pattern generator. Another possibility is that the AGC circuit isn't working right.

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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Mon 09, 2021 1:47 am 
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Jackmach5 wrote:
rcadanny wrote:
Those analog VHF tuners have a low band, channels 2 thru 6, and a high band, channels 7 thru 13. It's possible your low band isn't working if you're trying to get channels 3 or 4. Obviously, the high band that contains channel 7 is okay.


Ahh how would I go about troubleshooting that?

If the tuner contacts have already been cleaned, look to see if any are broken/bent. Also, observe that all wafers are turning when the tuner shaft is rotated. Don't disturb the physical position of any part if you can help it, but look at all resistors for signs of over heating. It's also possible a good checking tube may not work on both bands, try another tube if you have one.


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 Post subject: Re: Predicta Debutante Pattern Generator Works DVD player do
PostPosted: Aug Mon 09, 2021 3:15 pm 
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Joined: Feb Thu 18, 2021 3:09 pm
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I will take another look at the AGC circuit as well as seeing if the inside of tuner looks good. I have replacement tubes on the way to see if that is the problem as well.


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