My CTC-16XL Project. - Page 19 - Videokarma.org TV - Video

Electronic M · #**271** 07-03-2019, 10:52 PM

Possible. I just had a 21AXP22 I wrote off for dead when I bought the set it was in come back to life...CRT heater was open, but reflowing the solder on the base pins (after I verified the tube was still under vacuum) brought it back.

Sockets can fail too. The focus contact is usually first to go beacuse the ozone the HV generates corrodes the metal faster, but no harm checking them all though.

Yamamaya42 · #**272** 07-04-2019, 01:04 AM

I'm not sure what the problem is yet, but I know what it is not, I went ahead and changed the CRT socket anyway, this fixed the issue of the color changes I saw when I moved the wires around, but not the fluctuating in the blue level or the coming and going or the retrace, so just to test things , i swapped lines for the red and blue guns with each other, and the problem changed to red, telling me the CRT and pins are OK, and there is a problem with the B-Y amp or blue screen control, bad caps perhaps?
blue drive , i doubt, it has been cleaned ( deoxit ) 2 times.

Yamamaya42 · #**273** 07-04-2019, 12:42 PM

I don't get it, I'm still seeing some original resistors on the color PCB, if who ever worked on it before, was replacing so many, why stop?
R181,184,189 are old, and perhaps some others in the area, I can also see that the orange drop caps near the tubes are also old, this COULD be the cause of the changes in output level I am seeing when I turn the set on and it heats up.
I will see after I go over and replace them.

Yamamaya42 · #**274** 07-05-2019, 11:28 PM

Well, due to the holiday, i wont get my caps till Monday

But i did get my solid state focus rect, and it did NOT burn up, like the HV rect did.

so when doing the horz output cathode current check, it is now stable at 202ma

I MAY try again with another SS HV rect, IDK.

Bill R · #**275** 07-07-2019, 02:00 PM

You do know that retrace lines were always a problem with older sets and new formats like VHS, Laser disc, and DVD right? More a problem with the format than the tv. You may need to repair the IF and tuner to make them go away completely. As far as the set goes, retrace is often caused by to high CRT bias. Do a proper grey scale setup and it will help. I don't remember if the 16 had a separate crt bias control, but if it does turn it all the way down then try the grey scale adjustments of the screen controls. If one does not produce a line, then and only then turn up the crt bias just enough to get that line and reset the others.
As far as the solid state rectifiers goes, I never had much luck with them. They seemed to fail just as much as the tubes. Anytime I found one in a set, I took it out and replaced it with the tube. Remember the design engineers designed the circuit for tubes and their current draw. 202ma cathode current is still a little high. I would shoot for under 200 if possible.

Yamamaya42 · #**276** 07-07-2019, 10:05 PM

Quote:

Originally Posted by Bill R

You do know that retrace lines were always a problem with older sets and new formats like VHS, Laser disc, and DVD right? More a problem with the format than the tv. You may need to repair the IF and tuner to make them go away completely. As far as the set goes, retrace is often caused by to high CRT bias. Do a proper grey scale setup and it will help. I don't remember if the 16 had a separate crt bias control, but if it does turn it all the way down then try the grey scale adjustments of the screen controls. If one does not produce a line, then and only then turn up the crt bias just enough to get that line and reset the others.
As far as the solid state rectifiers goes, I never had much luck with them. They seemed to fail just as much as the tubes. Anytime I found one in a set, I took it out and replaced it with the tube. Remember the design engineers designed the circuit for tubes and their current draw. 202ma cathode current is still a little high. I would shoot for under 200 if possible.

As i mentioned, I don't have the equipment to do an IF alignment, nor have I ever done it before, so it is very unlikely that I will ever be able to undo the damage that was done to the IF section by the nut who had it before me.

The R/G/B - Y amps are sill unstable and change in output, so as soon as a grey scale setup is done, it's way off again 5-10 min later, as it warms up, still waiting for parts for that area.

I'm not too worried about the 202ma cathode current, but at this point there is little i can do about it, L40 horizontal efficiency coil has been core locked and i cant adjust it. a new one has been ordered, but the way it's running now is below the 210ma it says is the limit in the SAMs, and when I have it on, it's not on that long anyway.

Yamamaya42 · #**277** 07-08-2019, 08:53 PM

R/G/B -Y amps fixed and stable. am no longer seeing retrace lines.

https://imgur.com/veMo2go

The caps were def a problem.
So now I wait for new coil, and a chance to fix the cataract.

old_tv_nut · #**278** 07-08-2019, 09:07 PM

Quote:

Originally Posted by Yamamaya42

R/G/B -Y amps fixed and stable. am no longer seeing retrace lines.

https://imgur.com/veMo2go

The caps were def a problem.
So now I wait for new coil, and a chance to fix the cataract.

Makes sense, since these amps also apply DC restoration and horizontal blanking to the grids.

Yamamaya42 · #**279** 07-09-2019, 09:28 AM

For when I DO get the cataract fixed, I have seen no reference or diagrams as exactly WHERE on the neck the convergence yoke is placed, ( how far forward / back ) I can make a guess based on the markings, but, I have not seen it written anywhere that I can find, nor have I seen something for placement of purity rings or blue lateral.

Placement of them is probably not super critical, but then again, I can imagine that the placement of them a few degrees forward / back would have a visual effect. And find it a little hard to believe that there is no instructions / diagram someplace saying “this goes aprox here,” and so on.

Also, I have found the static convergence magnets quite hard to manipulate / adjust, no doubt have gotten tight over the years, any known way to make them slide easier for when final convergence is done?
Thanx.

Electronic M · #**280** 07-09-2019, 11:25 AM

There is a ring at the end of the electron gun the thickness of the convergence yoke that is closer to the glass then the rest of the gun....put the convergence yoke there. Place purity behind the convergence. Place blue lateral over the hump on the top of the blue G1 or G2 element.

Some convergence adjusters (there were many styles) you can add white lithium grease to in order to loosen.... don't want it too loose or adjustments will vibrate out of place when moving the set.

I have a Zenith service manual with a diagram but it will be a while before I can get to it.

Yamamaya42 · #**281** 07-09-2019, 11:37 AM

Quote:

Originally Posted by Electronic M

There is a ring at the end of the electron gun the thickness of the convergence yoke that is closer to the glass then the rest of the gun....put the convergence yoke there. Place purity behind the convergence. Place blue lateral over the hump on the top of the blue G1 or G2 element.

Some convergence adjusters (there were many styles) you can add white lithium grease to in order to loosen.... don't want it too loose or adjustments will vibrate out of place when moving the set.

I have a Zenith service manual with a diagram but it will be a while before I can get to it.

thanks

more or less, as seen here, then.
https://www.antiqueradio.org/art/RCA...ssingParts.jpg

Yamamaya42 · #**282** 07-10-2019, 06:55 PM

new coil came today, went in OK.

was able to adjust it down a bit
https://imgur.com/ou5q70O
https://imgur.com/2NZzNn4
still see some retrace lines once in a while, prob not much i can do about it with the video feed in, unless there is a way to mod the blanking amp.

oh well .

Yamamaya42 · #**283** 07-10-2019, 10:54 PM

i'm only seeing a 10v PtP wave on the plate on V21, no idea if this is normal or not

R203/204 are new, ( just replaced ) , C135 ( big orange drop) is not new, just ordered it , gonna try a new one to see what happens, this may not help at all, who knows.

old_tv_nut · #**284** 07-11-2019, 10:08 AM

You shoud have the same peak-to-peak waveform on both sides of C135, just different DC. If that's what you have, C135 is OK. This is the same AC waveform on all the color difference amplifier cathodes. Look at the waveform shown on the R-Y ampifier cathode. It is 15 v pp including both the blanking pulse and the signal, so I'd guess 10v pp for the pulse alone is OK.

Yamamaya42 · #**285** 07-11-2019, 10:39 AM

So, I'm still kind of wondering, should I even try to keep working on the IF section given the following...

When I got the set, there had been extensive work on the color PCB for a no color problem.
98% of all non power resistors were replaced, 5% of the caps replaced, and the bandpass coils.
Not to mention,it seemed the entire color PCB had been removed.

Upon going over the work done, I found several quality issues, including 4 resistors of wrong value, 1 cap with a lead open ( hanging), poor solder work and an issue with the color osc coil.

The most disturbing thing noticed is, the shield cover on the IF section was missing, but the bottom was on.
I could not see that any work was done in the IF, but chances are high that coils may have been messed with. (no way to know)

In the years of storage , the IF stopped working completely.
While testing , it was discovered that I could get color through via video injection at 1st video amp.

When checking resistors in IF section, found 2 that were open and about 2 out of tolerance, and the rest were just within tolerance.
After replacing the bad ones, I was able to use the tuner to lock in and get a good clear picture and sound, but w/o color.

And as mentioned earlier in the forum, I then focused on getting color working via video injection.

So, I am wondering this, 85% of the resistors in the IF section are still original that checked “ just within tolerance” but given the fact that chances are good that the coils may have been messed with, is it even worth the effort to replace the rest, given the state now that when I do try to use it I get a good stable b/w video and sound, would there be anything to gain in trying?
Or could it make it worse?
I have no idea.