ok here goes i have an analog meter and hv probe in bright down 24kv and not even half ma on the meter bright up around 23kv and even less then half ma. the arc was happening at the crt neck just a couple of times.

looks like r135 1.5 meg goes from grid of reg tube to hv adjust pot and horiz lin. c99 cap was changed its a .00
33 ceramic. the meter i used i know now that it has 5ma increments so the amount it moved i think its safe to say that i got .5 and 1.5 ma because it never got near the 5ma line.

ok now we are getting somewhere. try a new HV rectifier tube 1st. then check the sams see if it mentions adj the horz eff coil 1/4 turn to bring that shunt tube up to spec (.5-1.5 bright to dark). You may not be right at the lowest point but I think a minor tweek is allowed (no more than 1/4 turn).

When I setup a set the normal deal is to have a meter on the horz out tube cathode, a meter on the shunt tube, and the HV meter on the CRT anode.

adj the eff coil for lowest setting, set HV to 23-24kv, check shunt current, as long as there is some current flowing in the shunt with a full bright raster, then you should be ok (and the HV should hold steady at 23-24lv) If you have no current flowing in the shunt then you can reduce the HV to 22kv see if that does it. then try 20kv if still nothing then you can tweek the eff coil. It drives the fly a bit harder so you dont want to go overboard.

all of the above assumes there are no other issues. I would think a weak tube in the HV section would be the 1st place to check.



again your are trying for some flow of current in the shunt with a full bright raster, that shows you have some reserve HV and the regulation via the shunt should hold the HV steady.


I would also try another horz output tube/damper/hv rectifier. If the emissions are low on any of these HV performance will suffer.

i have tried several rec tubes, reg tubes , horiz tubes, and damper tubes nothing ever changed and i had checked the cathode current and with scene changes the cathode current would jump over 220ma so i had lowered it to a steady 200ma but i had raised it and lowered it with nothing ever changing for the better.

ok so you are seeing .5ma to 1.5ma depending on raster brightness? of so then shunt is working.

HV holds steady thru those changes (raster brightness)? if the shunt is working then this should be steady.


if the above is correct then maybe there is something wrong with the video output that is causing a bias issue at the CRT, the video output during normal siganals (not raster). Is this what is happening?

Not really.
If the regulator is not working then yes the picture will bounce with scene changes.
There is another problem though if the thing loads down, blooms, blurs out and the 3A3 filament dies.
Ok maybe I am talking out my ass, ignore me

the hv does not hold steady it will go from 24kv to 23kv so this is not steady. this is where the hv pot is at , max 24kv and if i lower it to 20kv it drops more with scene changes and tweaking the eff coil did nothing if anything i maybe got alittle as the hv probe needle moved up a speck when i lowered the ma to 190ma. i am about ready to air a nasty video of a silvertone in its last days,lol.

your right dan this is whats happening rec tube filiment dims blurrs, blooms, ect.:sigh:

you are worried about a 1kv change? that's it? a total of 1kv? from dark to light? are you serious?

How about C96 and C97? I have seen those go bad, they usually short.

A few kv or swing is not a problem and is normal.

When does it bloom?

no im not bothered by that but scene changes the hv drops from 24kv depending on the scene like white or others it will drop to 19kv. so its not regulating or something is dragging the hv down for whatever reason.

if those 2 caps are off the lin pot then no they were not changed.

I was talking to davewm and we agree if you are able to get the 1.5ma off the shunt, the hv is working ok.
Sounds like something is loading it down, overdriving the crt.

So if you get a commercial or something thats all white with text then the picture blows out and blooms??

no it actually dont bloom from that its only bwhen i wanted to raise the crt bias to brighten it up alittle thats when it blooms and when white scenes are present the picture goes alittle dark because theres not enough hv it seems. if i leave the bias ccw i dont bloom but different colors make it dark and i confermed this by watching the hv probe on different scenes bias down.

Maybe it had an esl dump.
Did you do the setup the way it says in sams under greyscale? Does that end up with the bias to high?
If you have a really strong crt the bias will be all the way down. You really only want to advance the bias once one of the screens is maxed out.

did the grey scale so many times now and it improves nothing. the thing with the drives,rgb i cannot get the rgb lines across the screen unless i raise the bias alittle then i put the service switch back to normal and then i have to lower the bias because its all bloomed. this is the only way to see the color line in the setup, nothing in the sams about bias at least that i remember. the strange thing is i can leave the rgb drives ccw and still have good color.

If that jumper is missing, put it back as soon as possible to restore the regulation. If your HV goes too high, the CRT neck may shear off. :eek:

its back....

HAHAHA its not a 70s Zenith, its a silvertone roundie that can hardly produce 24kv when hit by lightning.


Check the video output and voltages on the crt. I have a feeling something is being overdriven.

:tears::tears:maybe its time to just put it together and watch it the way it is rather then drive everyone including myself nuts. its been like this from day one and was told by don lindsly that something is loading it down and we were not able to figure it out yet. anyone want to buy a 63 silvertone,

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.

try a new video out. a weak video out will result in a darker than normal pic.

did that already:drool: to.

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.

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.

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.

[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? :scratch2:

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.

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.

did you ever check out the above? may account for the touchy pots

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.

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?????

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.

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:smoke:

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

oh did i tell you i got a brand new fly273 on ebay for 10.00. he had 10 flys for sale and i messaged him if he had another fly273 he said no but he said outbid everyone then pay the full amout and ill get the fly and a refund for the difference and he would put the other flys back on ebay. it worked out great got the refund and the fly273.

Everyone trips so hard on flybacks. I have never had one go bad on me, not even on the 16 I ran in a museum for 4 months the flyback held up. I have run across a few bad ones in old sets, maybe 2 in 100 sets. Not bad odds

well some people have your luck but mine is if not for bad luck i would not have any luck at all, all my flybacks would have probably gone bad if i didnt have a spare or 2 for each set including the 47 fada.

Hey Timmy do not feel bad I have the same luck sometimes I had only one bad fly and that was on a ctc 15 roundy but I sold that set years ago my bad luck is with crts I have a ctc16 that needs a new jug cause mine got broken during transport it brought tears to my eyes.. Timothy

Maybe when the stores run out of flybacks in the next few days from the panic buying you will be able to sell them for a few thousand each...?