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  #61  
Old 10-26-2012, 12:03 PM
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the voltages were very close at the crt when i checked it yesterday. in a previous post i wrote what they were. i think page 3. sorry its on page 2.

Last edited by timmy; 10-26-2012 at 12:13 PM.
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  #62  
Old 10-26-2012, 12:14 PM
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try a new video out. a weak video out will result in a darker than normal pic.
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  #63  
Old 10-26-2012, 12:17 PM
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try a new video out. a weak video out will result in a darker than normal pic.
did that already to.
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  #64  
Old 10-26-2012, 12:26 PM
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Did you try more than one video out? did it make any difference at all (always does on mine, every tube has a different gain, every tube resulted in a different level of brightness, some a lot some not much but there WAS a change.

since you seem to have issues going from normal to setup did you check ALL the parts in and around the setup service switch. Are you adjusting to a just visable line? does the sams say anything about where the brightness control should be set (matters on some sets).

does the contrast control work as is should? where is it set at? Many times the contrast is set too high.
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  #65  
Old 10-26-2012, 12:38 PM
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contrast control works fine, its at half. the problem here is hv not regulating and that it does seem that the hv is being loaded down. another video out tube i dont think will help but change little. the color lines i adjust to see then back off til just gone. and no i didnt check anything around the service switch. i think the sams did say something as to where the controls should be and i did what it said.
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  #66  
Old 10-26-2012, 01:00 PM
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Why do you say its not regulating, I thought you said the shunt current changed with the brightness and was between .5 and 1.5 with a dark to bright raster and the HV held to 23-24kv all signs that HV regulation is working as it should.

Now you may indeed have a over load that exceeds the ability of the HV to supply current at excessive beam current in the CRT, but this is unrelated to HV regulation. The shunt can only regulate within a beam current operating range, go beyond that and its NOT a regulation problem, rather its a load problem, You keep saying it like those can't be separated. you could confirm this by observing the shunt current when the blooming happens, the current should drop to 0 as the KV drops to 19kv. this would indicate the regulation is working as designed and you are simply overloading.

My guess is you are simply over driving the CRT to make up for a brightness deficiency real or imagined. there could be an issue with the service switch that may be making the setup not work properly, but that can be worked around, not all set had setup switches you just do it by eye with a live signal.

I am sure you will suddenly have the solution and it will all be fine.
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  #67  
Old 10-26-2012, 01:25 PM
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[QUOTE=ctc17;3052349]HAHAHA its not a 70s Zenith, its a silvertone roundie that can hardly produce 24kv when hit by lightning.




I always thought that any color CRT installed in any make or vintage of TV (not just 1970s Zenith sets) could have its neck sheared off from excessive high voltage. Were Zenith TVs the only ones to have this problem under HV runaway conditions?

If there is no regulation of the second anode voltage on the CRT, the voltage will go sky high, of course, until one of two things happens: the flyback burns out or the neck shears off the tube. Another problem when the 2nd anode voltage runs wild is excessive X-ray emission from the front of the tube and elsewhere. This is why all CRT televisions, from about the mid-'70s until the end of the CRT TV era, were equipped by Federal law with HV shutdown systems that would either make the picture unwatchable (by throwing the horizontal oscillator far off frequency, so far that no amount of fiddling with the hold control would bring the picture back into sync) or by blanking the raster entirely.
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  #68  
Old 10-26-2012, 01:43 PM
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More myths!

i believe X-Rays go nuts over 25kv, the crt may internally arc and crack at 30-40kv. Most all of the tube sets have a hard time producing 25kv with the crt and regulator disconnected.
The 70s solid sets with tripplers could go nuts but not the tube stuff.
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  #69  
Old 10-26-2012, 02:22 PM
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Originally Posted by miniman82 View Post
Sounds like a bad brightness control (or that bias pot you mentioned) to me, the blooming is caused by excessive current draw so if the screen brightness is all over the map that's where I'd start.
did you ever check out the above? may account for the touchy pots
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  #70  
Old 10-26-2012, 03:15 PM
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the brightness pot seems to be ok but turn it all the way down and can still see just alittle movement in the picture thats on the screen. its all crazy to me in that why does it take the hv adjust pot to be maxed to get 24kv. but what is overall overdriving or overloading this crt to cause this indirect hv thing. clearly the hv pot should not be maxed to get 24kv my other sets are alittle over the half mark at 24kv. the voltages at the crt i would think are somewhat ok since they are not reading off the charts, the readings i got are on page 2. the hvwill hold at 24kv providing there are no white scenes because the hv does drop so if its regulating the thing is now to figure out what is loading down.
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  #71  
Old 10-26-2012, 03:52 PM
ctc17 ctc17 is offline
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I would unplug the crt socket and the hv reg tube and see how high the voltage goes, then I would disconnect the hv from the crt and measure it in an attempt to verify there isnt something like a tad of air causing overloading.

But thats me, I have no fear of getting shocked or it arcing all over the place.

You changed the 3A3 right? Premium cigar rash?

Its common to fluctuate from 20-24kv, thats common and shouldnt be noticed.

Also, keep in mind how demanding modern content is on an old set. During the ntsc days they had all kinds of tricks to limit contrast and brightness. Subjects never work solid black suits on a bright white background. Thats why old programming looks washed out, that was intentional.
A strong crt+modern programming demands a perfect working chassis.

Good to use your hands, run it for 30 minutes, is the flyback hot? is the focus coil hot? the lin coil? etc

Sometimes just using a set that has been stored for years fixes alot of issues. Maybe its time to just use it gently for awhile and see if it wakes up.
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  #72  
Old 10-26-2012, 04:06 PM
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Unhappy

Quote:
Originally Posted by ctc17 View Post
I would unplug the crt socket and the hv reg tube and see how high the voltage goes, then I would disconnect the hv from the crt and measure it in an attempt to verify there isnt something like a tad of air causing overloading.

But thats me, I have no fear of getting shocked or it arcing all over the place.

You changed the 3A3 right? Premium cigar rash?

Its common to fluctuate from 20-24kv, thats common and shouldnt be noticed.

Also, keep in mind how demanding modern content is on an old set. During the ntsc days they had all kinds of tricks to limit contrast and brightness. Subjects never work solid black suits on a bright white background. Thats why old programming looks washed out, that was intentional.
A strong crt+modern programming demands a perfect working chassis.

Good to use your hands, run it for 30 minutes, is the flyback hot? is the focus coil hot? the lin coil? etc

Sometimes just using a set that has been stored for years fixes alot of issues. Maybe its time to just use it gently for awhile and see if it wakes up.
back when i was troublshooting with don lindsly i pulled the crt plug off and the hv came up and he had said something was loading the hv down. the flyback never gets warm and the focus coil is bearly warm and i had even checked the ohms of the focus coil and it matched the sams give or take an ohm or 2.i also had tried several 3a3 including a solid state one. i do remember pulling the reg tube cap and the hv went up alittle over 30kv and taking the anode off the crt didnt make a difference only pulling the crt neck plug made a difference but soon as putting the crt neck plug back the hv dropped. a small amount of air would do this?????
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  #73  
Old 10-26-2012, 04:17 PM
ctc17 ctc17 is offline
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An heres an observation....

I rewaxed a flyback out of one of these color sets. I boiled out moisture for over 90 minutes in a pot of wax that was 300F.
They are basically 90% paper and paper is hygroscopic and there has to be leakage through the paper at 24kv.
That very well could be your mystery load.

Speaking of hygroscopic, arnt yall about to get nailed by 3 record storms? Souldnt you be prepping for that and not worried about tvs? Making sure the car is full of gas, you have plenty of food, water, batteries a good working battery radio etc???
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  #74  
Old 10-26-2012, 04:36 PM
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Quote:
Originally Posted by ctc17 View Post
An heres an observation....

I rewaxed a flyback out of one of these color sets. I boiled out moisture for over 90 minutes in a pot of wax that was 300F.
They are basically 90% paper and paper is hygroscopic and there has to be leakage through the paper at 24kv.
That very well could be your mystery load.

Speaking of hygroscopic, arnt yall about to get nailed by 3 record storms? Souldnt you be prepping for that and not worried about tvs? Making sure the car is full of gas, you have plenty of food, water, batteries a good working battery radio etc???
well the flyback in the set was replaced and its a thordarson fly273 and its silicone potted and no arcing . so alittle air in this crt could have this affect afterall its the original that has silvertone on the neck plug. and the storm ahhh we will see if that happens even after the million dollar satillites they still cant get the weather right.
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  #75  
Old 10-26-2012, 04:43 PM
ctc17 ctc17 is offline
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Quote:
Originally Posted by timmy View Post
and the storm ahhh we will see if that happens even after the million dollar satillites they still cant get the weather right.
I wouldnt get caught with my pants down when you have a clear heads up.

I would be home watching the masses in total panic mode raid the stores of everything on my roundie totally prepared

Ok we can rule out the flyback...hmmm

You can try putting your crt tester on it in cutoff test mode, crank the cutoff voltage all they way up and see if you get blue glow in the neck. That would indicate gas/air.
The only sure way is to substitute

Last edited by ctc17; 10-26-2012 at 04:46 PM.
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