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 Post subject: Predicta Holiday Jitter
PostPosted: Sep Wed 08, 2021 9:54 pm 
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Joined: Mar Mon 30, 2020 12:50 am
Posts: 13
I have been working on a Predicta Holiday, and have come a long way since starting this restoration.

I have re-capped, tested and replaced tubes, replaced all couplets, replaced the RCA connector to the IF, cleared a solder blob short in the IF, and cleaned and tested all controls.

The set has a decent picture, but I now have a horizontal jitter that occurs every few seconds (see pics).

I would very much appreciate any guidance at this point.


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Holiday 1.JPG
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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Wed 08, 2021 11:38 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3506
Location: Dallas, TX
Hard to tell at this point, more details would help.
How long does each jitter last?
A fraction of a second might be due to a HV breakdown discharging and causing a glitch. Check the grounding of the external aquadag coating of the CRT, as well as any gaps in the coverage.
It could be a voltage breakdown somewhere else like a capacitor, causing a spike of interference.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Thu 09, 2021 4:21 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5415
Location: Woodinville, WA USA
Different TV, but my Dumont RA-113 had a case of momentary horizontal blips, tics, whatever you want to call them. They were cured by replacing a mica coupling capacitor in the horizontal section:

https://antiqueradio.org/DuMontRA-113Te ... zontalBlip

Mica caps are generally reliable, but some sweep sections beat up on them.

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html

Image

Image


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Thu 09, 2021 5:02 am 
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Posts: 48
I experienced something similar with a dirty H Freq pot in that model. Not the horizontal hold...the frequency control. A long shot, but that's rather what mine looked like.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Thu 09, 2021 8:17 am 
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Joined: May Sun 07, 2017 11:35 am
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Location: Belrose, NSW, Australia
Hor OP tubes have been known to arc internally like that, every few seconds or so. It looks just like that. It's generally accompanied by a fairly subtle arcing noise.

I believe it's caused by lead contamination of the mica inside the tube.

Try a new tube?

Could also be the damper.

Just looking at it again, it looks more like a displacement of the lines. So if a new tube doesn't fix it, suspect silver mica disease. If there is a mica in the horizontal oscillator that has a DC voltage across it (look at the circuit) that's very likely to be the fault.

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Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Thu 09, 2021 7:48 pm 
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Thank you all for your leads.

I will dig a little more, and see what I can find.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Fri 10, 2021 10:23 pm 
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I have replaced the 12DQ6 Horiz Output, the 12D4 Damper, and the 6CG7 Horiz Mult tubes, and no improvement.

I had previously changed the only silver mica cap, C43, 390 pF, in the Horiz Mult circuit, so I don't think that is it:

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I don't have a frequency control pot, but there is L22, Horiz Ring Coil. I have changed the .0039 uF cap parallel to that, but I am wondering if the coil could be open.

I timed the "tics"; around 3 seconds duration, 3 to 5 seconds in between.

I have not changed any of the ceramic caps in the Horiz circuits.

I would appreciate any further thoughts.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Fri 10, 2021 11:54 pm 
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Location: Albion, CA, USA, 95410
Long shot but...

I have a Predicta Holiday that started with an issue that looked something like that, then went dark, I had lost the HV. I have a thread going about it. Turned out that the horiz frequency inductor (L22) had gone bad. To find out if yours is being flaky like mine was, short out L22. If the jitter stops, it is the problem.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sat 11, 2021 12:17 am 
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Location: Ann Arbor, MI
Look around the horiz afc (horizontal automatic frequency control) circuit. If no problem there, look around the sync sep (sync separator) circuit.

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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sat 11, 2021 1:07 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Redlands CA
Are you using VHS tape as a source?

Old TV's often have horizontal issues with VHS.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sat 11, 2021 3:56 am 
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Sorry about the mis-named H Freq pot. I meant H range!


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sat 11, 2021 7:26 pm 
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Thanks madlabs, I will short L22 and test. I have been following your thread.

Tom, I will inspect the horiz AFC and sync sep circuits again.

Eric, I am using a DVD player as a source.

Hi jfleetwood, I will check the H range pot as well.

Thank you all again for your continued help.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sat 11, 2021 7:43 pm 
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Posts: 23671
Location: Haledon, NJ, usa
a bit off topic:

Ahh... nice nostalgic images there of HAZEL aka Shirley Booth.
In the 50's I really loved her show as a wonderful and funny maid.

Oddly enough... I just recently stumbled across an odd fact about her:
She is buried right here in NJ at Mount Hebron Cemetery in Montclair.
.... yeah... due to my recent health events.... I've been checking around to find a spot for myself for eternity ... lol ... and I have been seriously considering the very beautiful Mount Hebron cemetary.
And as chance would have it.. on Google search the fact popped up that Shirley Booth is there.

also... strangely coincidentally:
Some 20 or so years ago I used to love shooting some of my more dreamy, fine-art photo-images in that cemetery.
Here's one or two:
( http://pbpix.com/nw-21.html )
( http://pbpix.com/nw-22.html )

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To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sun 12, 2021 2:10 am 
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Posts: 10752
Location: Beaver Falls, PA. USA
If you have an oscilloscope, check the output of the horizontal oscillator. Also, check the B+ lines for any disturbance. One of the capacitors in K6 might be breaking down.

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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sun 12, 2021 11:00 pm 
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Peter, I'm happy that you appreciate Shirley Booth and "Hazel". I enjoyed that show in the 50's as well, and gave a set of DVD's to my wife. She tired of me using "The Day the Earth Stood Still" as my signal source, and asked me to use "Hazel" instead.

Thanks for sharing about her resting place at Mount Hebron Cemetery, and your photos, and I hope your health events are behind you.

Hi madlabs. I shorted L22 as you suggested, and the jitter disappeared for about 3 minutes. Then the horizontal went nuts (squiggly lines in the picture).

I removed L22, and it measures 1.9K ohms, instead of the 140 or 180 ohms per Sam's or Philco. Looks like I will need to find a replacement L22 before I proceed, as I expect the coil is opening when it gets hot.

Tom, I re-inspected the horiz AFC and sync sep circuits again, since I have the board out (again), and found some out-of-tolerance resistors that I will replace. Thanks for the tip.

Hi jfleetwood, I tested the horiz range pot again, and it is within tolerance, and does not seem to be noisy. I will check it again when the set is working again. Thanks for the tip.

Thanks again to all of you for your input.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Sun 12, 2021 11:01 pm 
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Joined: Mar Mon 30, 2020 12:50 am
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Tim, thank you for the leads. I will check those things when I have the set up and running again.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Mon 13, 2021 1:12 am 
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Posts: 1624
Location: Albion, CA, USA, 95410
Talon has a part that is supposed to cross-reference to the Philco part:

https://talonelectronics.com/shop/item.aspx?itemid=9543

I ordered the same part from epay for a little less. Interesting that your set needs it and mine doesn't.

Also, while you have the board off I would do all resistors, caps, couplates and tube sockets. If the buzz pot feels scratchy deal with that too.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Mon 13, 2021 6:34 am 
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Posts: 10000
Location: Redlands CA
Different model, but on my Predicta Debutant I had a similar issue that I thought was in the horizontal, but wasn't.

It had a glitch in the picture, accompanied by what sounded like arcing in the Flyback cage.
I cleaned everything, took the Fly out and coated it with new wax, checked grounds, and basically spent hours on it.

What it turned out to be was a bad wirewound Vertical Linearity Pot (1.5k with a 180 stop), it would arc and throw the sync off enough to cause the picture to glitch, the vertical did not collapse during these glitches, it looked more like a horizontal problem and the sound was exactly like that of an arc in the HV circuit.

Replace the Pot and fixed the problem.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Mon 13, 2021 7:06 pm 
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Joined: Mar Mon 30, 2020 12:50 am
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Thanks very much for the cross-reference and link madlabs. Not sure if my set actually needs it, but I would like to have a couple on hand, just in case. I have already re-capped, and gone through the resistors and sockets. All couplates have been replaced, and I have inspected and cleaned the buzz pot.

Eric, I will have another look at the Vert Lin pot. Appreciate the lead.

Again, thank you all for your help.


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 Post subject: Re: Predicta Holiday Jitter
PostPosted: Sep Mon 20, 2021 10:04 pm 
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Joined: Mar Mon 30, 2020 12:50 am
Posts: 13
Hello all,

I did have an open L22. Shorting it, then replacing it, eliminated the jitter.

For about 3 minutes the picture is great, then becomes unstable:

Attachment:
IMG_2793.JPG
IMG_2793.JPG [ 670.02 KiB | Viewed 325 times ]


I have gone through the Sync Sep and Horiz circuits, and have replaced 8 resistors. I have also replaced the 6AW8 Noise Inverter, 9BR7 Sync Sep and Horiz AFC, 12DQ6 Horiz Out, and 12D4 Damper, with no improvement. As I mentioned earlier, all couplates have been replaced.

I also replaced the Horiz Range and Horiz Hold pot pair, with no improvement.

I'm not sure if a new cap has failed. I will use my digital scope to check the waveforms again.

As usual, I would appreciate any guidance.


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