Zenith porthole 24G26 no vertical

[kramden66]

i might replace the resistors , the arc i thought was at the tube socket , well whats happening is theres an arc at the rim of the crt where its held down to the chassis and when it arcs there it arcs at the same time at the tube socket , now if it were just the tube rim why would it cause it to happen at the rim of the crt ? must be the reverse it happens at the rim and causes it to occur at the socket ? , i will take off the part thats supposed to insulate the rim from the chassis and clean it , perhaps even the doorknob is at fault causing the issue.

mike

[kramden66]

the plastic ring protector that goes around the rim of the crt had a couple cracks in it , i put electrical tape over the cracks and multiple layers around the metal piece that holds the crt , the plastic ring is supposed to insulate but wasn't properly after all these years , so it stoped arcing.
turned vertical height and it started to fill the picture but not as much as it should, so i'll have to check tubes , resistors , etc

mike

[kramden66]

incase anyone is interested it is filling out and set is running but no horz sync or very little and vertical sync is nothing great either , so sync search.

mike

[kramden66]

the fly - it gets hot , you can move the coating on it after running for 15 to 20 minutes , so either its being overdriven or its on its way out, it does show 12kv on the anode whick i think is normal for a 16ep4

[cwmoser]

Originally Posted by kramden66

the fly - it gets hot , you can move the coating on it after running for 15 to 20 minutes , so either its being overdriven or its on its way out, it does show 12kv on the anode whick i think is normal for a 16ep4

Make sure you have both 6BQ6 Hor. Output tubes and they check OK.
There is a common 100 ohm Cathode Resistor (R83). I read that the
cathode current should be less than 100ma. Instead of putting an
amp meter in series, measure R83 to see how close to 100 ohms it is.
Then power the set and measure the voltage across R83. Then
calculate the current. I understand too much current in R83 will overdrive
the Flyback and cause it to heat up.

There is an adjustment that affects this current - Hor Drive.
Adjust for best picture and less than 100ma.


Carl

[kramden66]

i don't have an amp meter but can turn the drive as low as possible before the screen starts squeezing , i will check the 100 ohm resistor , i'm pretty sure i already did

mike

[kramden66]

i just noticed my meter has AC ma and DC ma so i could measure the ma .... is it between the resistor and pin or the resistor to the ground or across the resistor ? this 100 ohm resistor is 120 ohms and replacement ( i put the 120 ohm by accident instead of the 100 ohm ) , its a power resistor , i could put a 100 ohm there or put a higher like 200 ohms to reduce the flow ?
also do i measure the ma at the horz drive or at the resistor? i'm just a little confused i never measured ma before or is what is on my meter not what i need to measure ?.

mike

[cwmoser]

I did not want to break the circuit so I measured the resistance.
Then powered th set with a volt meter across R83 - actually out of
curiousity I think I measured ac volts, dc volts, and used my
scope to look at the signal.
Then, I = E / R

Then adjusted Hor Drive to get current under 100ma

Let the set run for say 5 minutes, power off, discharge CRT anode, and measure temp.
These old Zenith portholes weak points are that they tend to eat up Flybacks. I wonder
if part of the problem is the way the circuit is designed and the other part the design
of the orignal Flybacks.

Carl

[kramden66]

i don't have a scope or a way to measure the temperature , i did notice that the sizzle or static electric sound that comes from the fly goes away when you turn the horz drive but it might go away only when the picture is being squeezed a little , i supp ose i could turn it down and readjust the vert size and lin to compinsate but it still might squeeze things .
I= E/R this is why i'm not licensed because i'm terrible at math.... you then say adjust till i get 100ma but your saying do this with math ? if i measured it would be more accurate wouldn't it ?.

mike

[Kevin Kuehn]

I= current in milliamps


E= voltage


R= resistance


Volts(measured across cathode resistor) divided by resistance(cathode resistor value in ohms) equals the current flowing through the cathode resistor.

Example:

10 volts/100 ohms = .1A (100ma)

[kramden66]

i did some experimenting and the closest i can get to .1 is .11 , thats altering the resistor from 100 ohms to 250 ohms , 27.5 volts divided by 250 ohms , with the 100 ohms you get 13 volts and .13 , so a 300 ohm resistor will probably take it down to .1 , i ran it with the 250 ohms and the fly wasn't getting hot , so i guess i'll have to either leave the 250 or raise it to 300 ohms .

mike

[cwmoser]

Mike, how does the video look with the 250 ohm resistor?

I've been told those 16EP4's were not aluminized and you can't expect
a very bright image. Best viewing is in a darkened room. It takes a
few minutes for mine to warm up before an acceptable image appears.

If you have a set with a 10BP4 CRT, the image will not be as bright or
sharp as the 10BP4.

This video is about as good as I was able to get my Zenith Porthole
in a darken room:
http://www.youtube.com/watch?v=aBdC_LdrZy0

Carl

[kramden66]

Well picture seems ok with the 250 volt resistor , this set shows a nice picture with a brightner on it , i had one in the past with a really good 16ep4 crt and it was as bright as this one is with the brightener , you might want to check resistors in the brightener circut because my original one was dark and a friend pointed out that it could be a resistor and bingo it was brighter because a resistor wasn't right, this one you can see without a brightener things getting a glow where there shouldn't be getting that silver or negative look , this doesn't happen with the brightener.

i do get lines but incomplete vertical retrace lines with copyguard that are bright and come and go , unsure if doing the retrace remover will work , reminds me of a zenith color roundie it did the same thing ......one other thing is if i want to fill the entire screen and stretch the horz to compinsate to make things properly proportioned i can't unless theres something to alter to do it , the 10" mayflower you can do it to , you miss more of the image but don't get people who are too tall and thinner but it doesn't have the expander switch , i know they were designed to expand verticaly but they should have stretched horizontaly too like the stromberg 10" when you push the expander switch.
Carl your crt is ok ?

mike

[cwmoser]

Mike, reading your post makes me want to do as you suggested and
check the resistors in my Brightness circuit.

I have not hooked my 16EP4 to a CRT tester.
I did not have my Sencore CR70 when I restored the TV.
Next time I unbutton this TV, I'll give it a go.

Thanks

Carl

[kramden66]

ok if you put a 300 ohm resistor there you get 30 volts across the resistor and it shows .1 ma , i have to rotate the drive a little so the picture will fill out on the sides but it remains 30 volts , even at 31 volts it remains close to .1

mike