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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Sat 25, 2017 6:15 pm 
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Location: Waxahachie Texas
Tom Schulz wrote:
Looking at the numbers on the end of the turret, it looks like the channel strips are arranged every other channel starting at 2 and then after 13 start over again with 3. Yet the channel selector knob shows the numbers in order. How does this work?

Locktite makes something called thread locker. But that is not what would have been used in this set. I also seem to remember that there was something called glyptol. But I think that that was red.


Tom,
The channel selector knob turns 2 complete revolutions to one complete turn of the turret. The first revolution gets either the odd numbers or even numbers, then the second gets the even or odd number channels. The gear ratio is basically 2:1 through the 3 gears in the system. The detent is pretty strong and the 2:1 gearing makes it easier to change the channels and there is some distance as far as rotation between channels. I guess this allows a smaller diameter channel selector knob too.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Sat 25, 2017 8:32 pm 
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Crist Rigotti wrote:
Tom,
The channel selector knob turns 2 complete revolutions to one complete turn of the turret. The first revolution gets either the odd numbers or even numbers, then the second gets the even or odd number channels. The gear ratio is basically 2:1 through the 3 gears in the system. The detent is pretty strong and the 2:1 gearing makes it easier to change the channels and there is some distance as far as rotation between channels. I guess this allows a smaller diameter channel selector knob too.

I suppose that that worked out well in practice since in any given market they tended to assign every other channel to avoid problems with adjacent channel interference. Since channels 4 and 5 have a little space between them, both could be used in the same market. So in most markets you would not normally be rotating the channel selector knob through two complete revolutions.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Sat 25, 2017 10:53 pm 
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Location: Waxahachie Texas
Let's get those strips mounted and the assembly installed.


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File comment: I mounted the cage to the main chassis and installed the "idler" gear. The idler gear was lubricated and bolted to the bracket, which was then screwed to the cage.
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File comment: I then soldered on the wires removed when taking off the tuner assembly. Then the tuner was installed on top of the cage using the witness marks left when originally installed.
I then screwed the first strip in place using the 2 4-40 screws and lock washers. I then carefully lined up the strip to the tuner and tightened the strip screws. This was repeated for all the rest of the strips.

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File comment: I then carefully rotated the turret and could hear some fingers clicking rather than a nice wiping sound. There were 3 strips that made this noise. After careful examination I could see that these 3 strips were bowed up in the middle. I then bent the mounting ears on the turret down just a little bit using an adjustable wrench.
Remounted the strips and the problem was solved. I had a nice wiping sound on all the strips. I then applied some DE-Oxit to each side of each finger on each strip, then ran it through the tuner contacts. I did this twice to be sure I had clean contacts. I then installed the cover to protect those strips.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Sat 25, 2017 10:55 pm 
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The tuning shaft was the next item to be installed. I lubed the end that was nearest to the gear, and the channel selector knob shaft as it passed through the front of the chassis.

I then aligned the turret with the channel selector by rotating the gear that attaches to the turret. I then tightened all the set screws and very lightly lubed the gears.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Sun 26, 2017 12:15 am 
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I installed the fly back and HV cage. No issues.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Mon 27, 2017 2:50 am 
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Location: Waxahachie Texas
I replaced the 2 560 Ohm yoke resistors and the 56pf 1Kv cap. I used a 56pf 3Kv COG disc cap. None of these 3 components were listed in the Sams parts lists but were listed in Riders.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Mon 27, 2017 3:57 am 
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Tomorrow I should be able to attach the yoke and focus coil wires. Then do my resistance check. Then if all is good, then the first power up.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Mon 27, 2017 6:42 pm 
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Crist Rigotti wrote:
I used a 56pf 3Kv COG disc cap.

As you have noticed, ceramic caps come in a wide variety of types. For some ceramic caps the value of the cap varies quite a lot as the applied voltage changes. I believe that the ones that do that are also the ones that have wild tolerances and wild value changes with temperature. Those are generally the high value caps where the more stable ceramics would create an excessively large disc and possibly cost more. I believe that the cap you chose should work well. But if you should have stubborn problems with horizontal linearity, you should try a mica cap instead of the ceramic cap before giving up.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Mon 27, 2017 8:40 pm 
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Tom Schulz wrote:
Crist Rigotti wrote:
I used a 56pf 3Kv COG disc cap.

As you have noticed, ceramic caps come in a wide variety of types. For some ceramic caps the value of the cap varies quite a lot as the applied voltage changes. I believe that the ones that do that are also the ones that have wild tolerances and wild value changes with temperature. Those are generally the high value caps where the more stable ceramics would create an excessively large disc and possibly cost more. I believe that the cap you chose should work well. But if you should have stubborn problems with horizontal linearity, you should try a mica cap instead of the ceramic cap before giving up.

Tom,
You are right about the cap. I used it because I had some left over from another TV project. Mouse has a 56pf 1Kv mica cap that I just might pick up and use.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 3:26 am 
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Location: Waxahachie Texas
The resistance check so no errors.

I then powered it up with the rectifier tubes out. The filaments all glowed nicely. Then rectifier tubes in and I got B+ voltages. The high B+ reads 328V vs 360V and the lower B+ reads 186V vs 130v.

I have 11.5Kv and the picture looks washed out. All I've done so far is adjust the front controls. V Lin, V Size, Bright, Contrast, H Hold, V Hold, and the Buzz control on the back.

Any idea as to where to start? BTW, the test CRT is an 8YP4 with the adapter harness.

Here's a video of what I have.

https://youtu.be/1U6SL5BV6-Y


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 1:12 pm 
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I had a similar issue. This helped me.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 4:41 pm 
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Well at least you have some sort of video and sync. I'm surprised by the amount of "hum", since you replaced all the E-caps. I would suspect that it is being picked up somewhere other than the power supply. Bad ground?
Since one of the B+ supplies is high I would suspect that some section isn't pulling its normal current, maybe the sound section.
I know you replaced all the caps, resistors and suspicious tubes already.
Besides the video detector, maybe you have leakage in a connector or a bad connection.
The resistance tests can't always catch everything.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 5:06 pm 
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shovelhead13746 wrote:
I had a similar issue. This helped me.


Yup, I replaced the video detector with a 1N34A diode.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 5:13 pm 
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Notimetolooz wrote:
Well at least you have some sort of video and sync. I'm surprised by the amount of "hum", since you replaced all the E-caps. I would suspect that it is being picked up somewhere other than the power supply. Bad ground?
Since one of the B+ supplies is high I would suspect that some section isn't pulling its normal current, maybe the sound section.
I know you replaced all the caps, resistors and suspicious tubes already.
Besides the video detector, maybe you have leakage in a connector or a bad connection.
The resistance tests can't always catch everything.


Tim,
Yeah there was a lot of hum. It did get better.
As I get further along with checking things out we'll see what gives with the power supplies. Riders lists the voltages as 382V and 187V. So it looks like the B++ is the one that's a little low. Just checking the power supply, with out the main chassis connected, the B++ was at 352V with no load. So it looks like the main chassis is loading down the voltage of 24V. While the just the B+ isin't loaded down at all.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 5:25 pm 
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I suppose the hum could have actually been the vertical signal getting into the sound.
I notice the SAMS doesn't show scope waveforms. You could compare signals with those of a working set of approximately the same vintage if it came down to it.
I would start with the sound if there is still a problem, because it is easier to trouble shoot and may lead to discovering something that is causing another problem.
The picture looks pretty good now.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 6:41 pm 
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Does the hum diminish with the volume control turned all the way down? I believe there is a "buzz control" on the back of the chassis for minimizing intercarrier buzz. Otherwise it likely could use a sound IF alignment. On the power supply voltages - you wouldn't by chance have the 5U4 and 5Y3 interchanged?


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 11:57 pm 
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Kevin Kuehn wrote:
Does the hum diminish with the volume control turned all the way down? I believe there is a "buzz control" on the back of the chassis for minimizing intercarrier buzz. Otherwise it likely could use a sound IF alignment. On the power supply voltages - you wouldn't by chance have the 5U4 and 5Y3 interchanged?


Yeah it does.

I've messed with the buzz control and it makes a big difference!

Good question but the tubes are right.

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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Wed 29, 2017 11:58 pm 
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Here is where I am using the original CRT that tested on the low side of good. All I've done is twiddle the front and back controls.

I have another CRT that tests on the high side of good. I'll use this one for awhile during set up etc.

I'm a happy camper.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Nov Thu 30, 2017 12:22 am 
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I'd say your Video IF alignment is close to ideal.


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 Post subject: Re: Zenith H2447R 19" Porthole TV
PostPosted: Dec Sat 02, 2017 6:53 am 
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Bit of crushing at bottom of raster. Check cathode bypass cap on vert. output tube.
Nice job you've done on that chassis!


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