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  #16  
Old 08-01-2018, 10:21 PM
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Notimetolooz Notimetolooz is offline
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Ha-ha. I told you TVs are complicated.
The horizontal yoke winding is used in conjunction with the flyback to generate the CRT high voltage.
Those TVs with the CRT separate from the chassis are a pain.
A good time to remind you that CRT are delicate and dangerous. Separating the CRT from the cabinet means great care must be used. Probably best not to remove the CRT from the cabinet. Back in the day TV repairmen usually drove a panel truck to haul the TVs. Another trick was to use special small test CRTs that could work well enough with the original yoke and CRT socket.
He could leave the CRT and just take the yoke and the chassis to his shop.
If you haven't checked out "Phil's Old Radios" website, he has a number of interesting articles about TVs.
https://www.antiqueradio.org/8XP4PictureTube.htm
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  #17  
Old 08-01-2018, 10:37 PM
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What make and model is the set?
HiFi audio is straight forward compared to even a B/W TV, a schematic is practically mandatory unless you have a lot of experience with TVs. A TV that old might have a free schematic available if it is a major brand.
SAMs Photofacts many times will have scope waveforms to look for as well as adjustment procedures.
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  #18  
Old 08-01-2018, 10:49 PM
Sealtest Sealtest is offline
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I don't plan to remove the CRT from the cabinet. I hang out at the local E-waste facility a lot and have seen many people drop CRT sets with the mentality of "I don't have to be careful with this thing since I'm throwing it away". One loud boom and a broken CRT later they know not to do this.

Anyways I am going to try scoot the chassis out of the cabinet just enough to try and get at the bottom. I will be very careful of course.

The tv is a RCA KSC92-a chassis. I have the manual now and is has waveforms in it, but without the CRT all the voltages go wonky and I could not get most of the chassis to have proper power. It does mention the procedures for HV adjustment but they all have the CRT showing raster so they may or may not apply. I just don't understand how an oscilloscope will help when turning the controls for the HV never gets it where it needs to be. The pitch changes but never goes high enough.
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  #19  
Old 08-01-2018, 11:38 PM
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If by adjustment for the HV you mean the Horiz oscillator adjustment procedure, the scope is needed to adjust the wave shape of the osc. There are two slugs in the osc coil one is primarily for the shape and the other is primarily for the frequency, BUT they interact with each other.

With RCAs (when adjusting the H osc) I tend to scope video and set the scope up to show 2 to 4 H synch pulses and count the scope scale divisions between the leading edges of the tips. Leave the scope time scale untouched and connect it to the horizontal. I then adjust the horiz oscillator coil slugs to get the peaks of the waveform the same distance (read divisions on the scope screen scale) apart as the video sync peaks were while maintaining proper wave shape illustrated in the sam's...It is not hard to do once you've done it once or twice.

There may be other controls like Drive, linearity and width that need to be tweaked for best/correct operation.

IIRC the yoke plug on that is octal. You can extend the yoke by robbing an octal socket from a junk set, taking the base off a dud octal tube and some wire and making an octal extension cord...You can do the same with the HV lead (you'll need a big screen BPC CRT set to rob the HV cable from), and the CRT socket (brighteners will give you all you need except the wire).
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  #20  
Old 08-02-2018, 01:54 AM
Sealtest Sealtest is offline
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Yes I mean the Horiz oscillator adjustment procedure. I have looked in the manual and tried to follow. The process doesn't seem too bad by any means, there is just the fact this is my first time trying this and so far there have been many snags. Tube sets have always been so cool and satisfying when you save one from the dump, but fixing them has been another story.

Good info on the adjustment. I am trying real hard to get this sorted, but has there ever been a case where the Horiz oscillator can not be gotten close enough to be adjusted with a scope? That is the worry with this set so far. I can adjust and change the pitch of the HV but it is never even close. In the manual for this set there are many troubleshooting processes but none that have the Horiz working while also having no raster. At this point it looks like it may be best to try harder to find someone local who can give some hands on guidance with this.

Yes this set has the drive, width, etc. Adjusting those did not change anything, but they probably just made it worse. Oh well it is a learning experience.

Sounds like it's time to search for more junk sets. So far the couple tube sets I have are the only ones that have shown up in years of searching the area. Before doing anything it looks like this set has a lot of slack and extra wire so I will scoot the chassis out with everything hooked up and see how many test points are accessible. Something to do tomorrow or in the next couple days.
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  #21  
Old 08-02-2018, 10:39 AM
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The extension cables are a good idea and getting some parts from brighteners is good also.
In other posts you said that you have stuff from closed TV repair shops. You might find things like extension cables and test CRTs among the items. You could find brighteners there also. Maybe replacement yokes too.
I didn't mean to imply that a scope should be used for every troubleshooting problem. You can determine frequency with your scopes to within about 5% which is plenty good enough in cases like these.
The way that the flyback circuit works it can only produce the high voltage if the frequency is within a certain range. I've seen parts destroyed because the frequency is way off. The horizontal output circuit is one that handles a lot of power and parts are under a lot of stress even when working normally.
If the horizontal oscillator is off frequency it could be due to many things, bad resistor, capacitor, coil, tube, bad connections. You seem to have some evidence that the problem changes with temperature so when you test these components individually they might not show that they are bad. You said you replaced all the capacitors, did you use the right type in each location? The CRT itself doesn't take a lot of current so having it disconnected shouldn't effect chassis voltages very much. Things like the yoke and the focus coil (if your set has one) need to be connected.
Since I don't have the schematic, if you could scan the section containing the horizontal area and post it that would help.
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  #22  
Old 08-04-2018, 10:01 AM
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Kevin Kuehn Kevin Kuehn is offline
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Quote:
Originally Posted by Sealtest View Post
I just don't understand how an oscilloscope will help when turning the controls for the HV never gets it where it needs to be. The pitch changes but never goes high enough.
The scope can visually verify that the frequency and shape of the horizontal oscillator frequency waveform is within the ballpark, and you will see how the controls change it's shape and frequency.
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