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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sun 14, 2018 5:29 am 
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Location: Waxahachie Texas
Oops! Made a recapping error! Before I do an alignment I take small pieces of masking tape and ID the places I need to hook to during the alignment. In the Sams these consist of letters A thru F. All went well till finding test point F. Test point F is at the junction of R22, R20, and C13. When examining that spot I noticed that C13 wasn't at the junction! It was at the "bottom" of R20. I checked my notes and sure enough I soldered C13 to the wrong terminal. I soldered it to terminal 3 (counting L to R) instead of 4. I easily moved it to the right spot and labeled test pont F. I never would have caught that if I wasn't pre-labeling those test points. Excuse me while I go buy a couple of Lottery tickets!


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sun 14, 2018 6:00 am 
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Location: Waxahachie Texas
The picture is getting better by just watching TV. Star Trek to be exact.


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sun 14, 2018 6:16 am 
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Hey Crist, you are doing an amazing job on that set and the pics look great!
Often, the picture will improve the longer you run the CRT. I've seen that happen.
But I can't help but think that you'll end up with a replica rather than a restoration if you use the shotgun approach and replace everything. Example: The 15k resistor inside the coil can - it had no gold or silver band so it's a 20% tolerance resistor. Which means 23k would still have been OK..... And the inductance of a replacement carbon film resistor will affect the inductance of the coil. Still, you will have corrected for that during the alignment.
I don't know about those wafer micas, where I come from (Australia) micas NEVER fail! You don't even think about replacing a mica cap, ever! I guess they must have known about silver migration when they made them here.....
Do you use a surface-mount-reworking type hot air gun and long-nose pliers to remove the old parts? If not, it may be worth the investment for next time, they really work great. I would never have discovered this except I bought one to aid SMD prototyping/debugging in my day job!


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sun 14, 2018 6:36 am 
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Location: San Jose, CA USA
irob2345 wrote:
The 15k resistor inside the coil can - it had no gold or silver band so it's a 20% tolerance resistor. Which means 23k would still have been OK

Better check that math. :) I think I'll go with Crist's calculator on this one...

In general, I agree with you -- I like to leave more of the original components in place. But everyone has their own approach, and seeing what everyone else does makes this hobby interesting.

Interesting that you don't see any mica failures down under. Must be the Coriolis force pushing all those silver atoms back where they belong!

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sun 14, 2018 8:03 am 
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Yes you are right about the maths. Got to watch that mental arithmetic! 18k and 12k are the 20% limits for a 15k resistor. If I have to replace a carbon composition resistor that's part of a tuned circuit I'll use a surface mount part, a 1206 if I can get it.

We do see silver migration here, early 50's Mullard 6M5s are a good example.

One type of old mica cap we had was moulded in light brown bakelite labelled "Simplex SM" I used to think that stood for Silver Mica but it's actually means Stacked Mica. Never seen a bad one in over 50 years!


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Tue 16, 2018 7:56 pm 
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I'm done with the alignment and now on to some details.
I noticed this from the beginning. There some white horizontal lines that "flash" every so often. They are usually near the top of the screen. This happened before I did the retrace blanking mod. They increase in brightness with the "Brightness" knob. If the picture is just a little too dark, they almost disappear.
I've cleaned all the tube sockets and their pins.
Any ideas. Thanks.

https://youtu.be/cFoYIfubVkY

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Tue 16, 2018 11:22 pm 
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What is your video source?

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


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Tue 16, 2018 11:48 pm 
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Adjusting the size of the resistor and capacitor in the retrace blanking circuit is sometimes needed to get it to really blank well. Since you may be seeing incomplete blanking, try increasing the capacitance and/or increasing the resistance in that circuit.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 12:54 am 
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philsoldradios wrote:
What is your video source?

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


Phil,
I just tried injecting the video directly to the video amp tube. Same thing. I also tried a DVD player and got the same thing.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 12:55 am 
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Tom Albrecht wrote:
Adjusting the size of the resistor and capacitor in the retrace blanking circuit is sometimes needed to get it to really blank well. Since you may be seeing incomplete blanking, try increasing the capacitance and/or increasing the resistance in that circuit.


Good suggestion. I'll try clipping in more capacitance.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 1:05 am 
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No joy adding more capacitance. I didn't add any more resistance because I would have to unsolder the 220K. I'll do that a bit later.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 1:38 am 
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Crist, it is your source. It's just about impossible to fix your vertical blanking circuit with passive component changes so that it will work to fix this without impinging on the top of the picture. I found you need to add a monostable circuit.

Here, pasted from a magazine article I'm writing, is an explanation. It's written for our local scene but the same applies in the US. Your biggest bogeyman is Macrovision on the DVDs. It also covers sound, which you may not have come across yet.

"
But, depending on the TV and the material you are playing, you may notice issues such as diagonal white lines and interference in the sound, spoiling your enjoyment of that classic movie or TV show.

Why does this happen? Well, the short answer is that the more modern analogue TV signals are different to what they were in the 1950s and 60s.
What are these differences?

Firstly, in the late 1960s in readiness for colour, the transmitted sound carrier power was quietly reduced from 25% of peak vision power to 10%. The main effect at the time was that many older TVs became more critical to tune for good sound.

The second change was the “discovery” in the mid 1970s of the Vertical Blanking Interval (VBI) in the TV signal. The VBI is effectively the time that was included in the TV signal to allow the scanning beam in the receiver's CRT time to return from the bottom to the top of the screen (vertical retrace). Prior to the mid 70's, the VBI contained no information, just black. Then John Adams at Philips in the UK came up with the idea of transmitting text data in this otherwise wasted time. Teletext was born.

Other uses soon appeared for the VBI. Amongst these were Vertical Interval Test Signal, Time Code and, once home videotape appeared, a number of copy protection schemes, notably, Macrovision.

All these systems had three main attributes. They became embedded in the recorded video, they were virtually ubiquitous and the VBI was no longer black.

Why should this be a problem, since even vintage TVs have vertical retrace blanking circuits? The answer is, it turns out to be almost impossible to fully blank peak white signals that occur in the VBI using available internal signals in the TV and passive circuits. So, because it wasn't really necessary, early TV designs simply didn't do it. Even some early colour TV designs were embarrassed by signals in the VBI and required field modifications.

VBI signals cause another problem. When fed to most RF modulators, the peak white excursions of the data in the VBI completely cut off the vision carrier. This action “punches holes” in the FM sound carrier, causing an annoying buzz in the sound. You might remember this buzz from the days when you operated your TV through the VCR, using the “VCR” channel.
"
I've developed a box to fix this, it's detailed in a recent post on this forum.

Oh, yes, if you want to see what's going on in the vertical blanking interval, use the TV's vertical hold to roll the picture so you can see the blanking bar. Watch what goes on in there. You'll see a series of lines and dots that come and go, varying in brightness. That's Macrovision. You'll have to get rid of that s**t from your video signal.


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 4:04 am 
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irob2345,

After reading your previous post I remembered that I could hook my computer to the TV and play videos I recorded here at home with my own camera.
The results were pretty much the same. Though an HD recording does look nice on the TV screen. Very nice indeed, except the occasional white line flash in the upper 1/4 of the screen.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 4:36 am 
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That's timecode. Roll the picture through and look at the blanking bar. You'll see it.
All sorts of devices put all sorts of s**t in the VBI for all sorts of reasons.....
Moderns sets know about this and can blank it out.
In the late 60's AFAIK Philips introduced what they called a sandcastle pulse into their TV chipsets. This is one of the reasons. The idea was a good one and copied by just about everyone.

My Kriesler 79-2 (1958) suffered badly from this problem. No amount of playing with time constants would fix it.

Oh what CAN fix it is transcoding the content using VLC - this will remove anything in the VBI - and playing the file on a media player that doesn't add its own **deleted** to the VBI. Most don't.


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 4:42 am 
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The script works!
Couldn't have put it better myself!


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 5:37 am 
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irob2345 wrote:
The script works!
Couldn't have put it better myself!


????

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 6:10 am 
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I'm starting on the cabinet now. I remember reading somewhere what it takes to remove the channel plate that is usually warped. Can anybody point me to where I read that? I don't want to break that Channel number plate!
Thanks.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 6:52 am 
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I got the Channel Plate off with no problems.

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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Wed 17, 2018 7:29 am 
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Re the script working:

Web forums usually run some automated tools to process incoming posts and, in this case, to delete a slightly vulgar 4 letter word starting with s. These are usually implemented by scripts.
My reason for the comment was, the sentence read better when the word was deleted, replaced by deleted!


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 Post subject: Re: Scored an Admiral 19A11
PostPosted: Jan Sat 20, 2018 3:21 pm 
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I've cleaned and polished the cabinet. Then I refilled the lettering on the front of the cabinet like Bob did on his video. I used some satin acrylic paint from Walmart and it turned out pretty good. Then I got to thinking that he used white on his black cabinet and I also used white on my brown cabinet. Looking at it now, I'm thinking I should have used perhaps a light tan or Khaki color. I scrapped the lines on the Channel Plate and they stayed a Khaki color. What color did Admiral use on their brown cabinets?


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