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  #16  
Old 07-14-2012, 09:55 PM
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most of the crt,s i replaced nos or rebuilt would snap pop for a couple minutes then be fine. i don,t know the cause but never had a problem with them. i put a nos rca in my ctc68 a few months back and it had a loud snap at first power on nothing after that plays like new. i think your ok on the sanyo tv. steve
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  #17  
Old 07-14-2012, 10:29 PM
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It could very well be the effects of a new CRT; but, I'd still want to know what the HV and focus voltages are before going any further. Something caused that old CRT to crack and you want to make sure the same thing does not happen to your tube.
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  #18  
Old 07-14-2012, 11:07 PM
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Well, I just went ahead and hooked up the HV to it.

And IT WORKS! It made another loud pop, but about half as loud as the ones in my video. Followed by the normal snapping sounds as you'd expect.

Picture came up and it is working just fine!

Other than you can tell the old tube, despite having 100% emissions, was a bit worn. The screen greyscale is a bit bright, and the focus is a bit off, but much, much sharper at the edges than the old CRT. Even still the old CRT still looked amazing.

So all it needs now is the convergence and it looks like either purity or it needs degaussed in the lower right of the screen.




But as I was getting all excited, the TV decided to shut itself back off and won't come on again. And I know what it is now: That power relay. I've had this TV for 6 years in storage now, and I now remember I did resolder the connections at the power relay to no avail about 4 years ago. I went in and wiggled the power relay and the TV decided to come on! So I resoldered it 2 weekends ago completely forgetting I already did that 4 years ago, and all of a sudden it started working. This was the same night I broke the original CRT. So on with the hunt for a new power relay at this point. Coil appears to be intermittent.


As for the CRT neck cracking on the old tube... I don't know if it had to do with that internal short I got (it was an extremely bright purple when the tube was on) and maybe I accidentally hit the neck wrong with my screwdriver handle trying to see if it made any difference on my tester after realizing I just screwed the tube up. I was not happy that night, and I might have accidentally hit it too hard after giving up knowing there was nothing I could do for that tube... it was toast at that point.



Anyhow, what I just witnessed was a first. I can understand some loud pops from a brand new CRT, but these were extremely loud with those color flashes. It just scared me. But now I know. Lesson learned on multiple things just from this. I will also check the high voltage in this set once my HV probe comes.


I will keep you posted once I get it functional yet again.


Thanks!

Last edited by tv beta guy; 07-14-2012 at 11:16 PM.
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  #19  
Old 07-15-2012, 03:44 PM
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This is becoming quite an adventure here....

The problem now is not the power relay. Everything tests fine and put it back in.

Now the digital control board isn't working. Press power, and no voltage (12VDC) is on the coil of the relay.

There is a power regulator there that may be the culprit. Didn't have time to troubleshoot any further.

But recall how I said the TV randomly turned itself on when I plugged it in while I had the neck board off? It did that more than once, and only happens when you first plug the TV in. When it does that, the sound comes on, then slowly fades out, and I have no control. I had to turn the TV off, then back on. One time it did that it randomly started advancing channels on its own. It could have been that voltage regulator failing and putting out the wrong voltage causing erratic behavior.

The microprocessor is a long socketed IC. I think I should look up the datasheets on that and see where the input voltage is fed, and see if that is wrong.

And to make things even more complicated, not only do I not have the model #, I cannot even locate a chassis number. Just part numbers all over everything that doesn't help. I know I need to get a Sams Photofact so I can check other voltages at this point.

It could be multiple things, and I am not going to be able to get back into this set till next weekend.
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  #20  
Old 07-15-2012, 06:07 PM
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well, I think your old tube arced through the neck, to the yoke, like zeniths with that bad safety cap. That most likely cracked the tube, and gave you the short reading.

I bet your relay kicking on and off is the HV hold down circuit. If the voltage goes up, the set shuts off. but its only a guess. It was a thing on those sets around that date. Look for a long IC in the middle of the H and V circuitry, and look for a pin with either "hold down" or "0V" printed on it. If you can get the set to run, with the board set for you to measure the 0V pin, if it goes up, ground it temp, to see if the set comes on.

Take the number off that IC and get a pin-out, not as good as a schematic, but you can see the 0V pin.
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  #21  
Old 07-15-2012, 06:28 PM
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It did not crack where the yoke was at... I just kept calling the whole piece where the guns are at the neck. It cracked starting from the pins and evacuation nipple. And it was probably because after I gave up on the CRT since it was toast, I might have tapped it a little too hard by accident trying to clear the short.

The purple arcing inside was from whatever damage was cause by that discharge from the CRT neck board. I don't know why that happened, because this is the first time I've seen something like this happen. That did the CRT in right there.

But my problem now is indeed localized to that logic board that controls the digital tuner, power on/off, etc. As I said it was acting up when you first plug the TV in prior to all this (randomly turning itself on with no audio or control). And now it just finally quit working.

When you first plug the TV in, the LED channel display used to briefly light up 00 for like a fraction of a second when it was working correctly. Now it doesn't even do that. I'm suspecting that voltage regulator, or surrounding capacitors, etc. might be bad. There isn't too much to that board. I am going to try to find the data sheet on that micro controller IC and the voltage regulator, and see if at least the voltage inputs on it are correct for standby power. If not that is probably it.
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  #22  
Old 07-24-2012, 10:31 PM
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Status Update

Well after spending last night and today troubleshooting the logic board, I finally found the problem.

Without a schematic, just tracing everything out. Turns out the relay does not get its power from the output side of the voltage regulator (which is 12VDC). It just grabs it from the incoming side which is 16VDC. Uses a dropping resistor in series with the coil to allow it to operate at 12V.

Followed that all the way down to the shorting diode right before the relay coil. Still read 16V. Get to the relay, and with the TV off, fluctuating between .7 and 1.3V at random. Shouldn't be doing that as there is nothing else between the diode and relay. Shorting diode tested good. From the other side of the relay goes to the collector on the switching transistor. Turning the TV on, Base to Emitter was .7V which is right. Collector to Emitter was 0V, which is right. But still that small fluctuating voltage on the coil.

Long story short, I jumped it from the diode to relay and the TV turned on when I pressed power. Apparently there was an intermittent/bad trace on the board. I just soldered a wire in place and now everything is working fine again.




But now, the same CRT problem remains....

The TV still snapped, but not loud like in my video (which I took down because that link was unlisted and just for this site, and somebody was rather rude to me about my TV, telling me to junk it and get a Sony.)

So I let the TV run for a good while. No problems, razor sharp picture. Adjusted the purity and got that looking great. After about 15-20 minutes the tube started to snap again, about once every couple of minutes. Nothing as loud as the original video, but enough to cause the picture to jump and make you turn your head.

Went to do greyscale. Put the TV in setup mode, which is a jumper on the board. I did that with the power off. When I turned the TV on, it snapped again, and I noticed in setup line mode, the neck of the tube where the heaters are at was glowing a slight blue (looked like it was reflecting on the glass though from something further up.)

It got a little bit brighter as I watched it and it snapped again with a blue flash. Then the blue glow went away.


It started glowing blue again after a little while, and I just decided to shut the TV off. I didn't even get to do greyscale. When I shut the TV off, it snapped again, but this time a big blue flash in the neck of the tube.

Now when I was operating the TV normally without the setup line, no blue glow in the tube at all. It ran just fine for about 15 minutes, with the occasional snap here and there. Even shut down fine with no snapping.
While testing it with the test jumper earlier with the power relay problem, I just touched the lead to the relay coil and the TV came on, then I disconnected the lead, turning the TV off after I verified it worked. The TV just gave another snap a couple seconds later with no weird activity in the CRT neck.

Also to note, when I ran the TV without the second anode lead hooked up, nothing bad happened there either. This is only occurring when the HV is applied to the tube.






Just to run down a few things:
1. I cracked the tube on the old CRT. I accidentally tapped it too hard near the pins and that is what cracked it. It was already after the original CRT was beyond repair so really it was nothing to lose at that point. It wasn't up near the yoke or anything.
2. I shut down the TV in the video by pulling the plug as soon as I heard it snap. It wasn't the excessive HV shutdown protection.
3. The original CRT did not have a HV problem at all. The problem was something shorted in the neck of the tube as it affected my Sencore CRT tester. This new CRT everything tests perfect on the tester, and the TV does operate perfectly minus the occasional loud snap. I've only had this CRT on for 15 minutes total. I wasn't going to worry about that
4. What concerns me now is that blue glow and bright flash upon shutdown in the neck of the CRT when in setup line mode. Doesn't do any of that when running the TV normally.



All CRT grounds in place and hooked up. I'm just wondering what is going on here. Everything works as it should when it was on. Picture looked perfect, perfect focus, everything.
Nothing is physically burnt or blown. The CRT neckboard is fine. Picture was the right size and everything.


These are just all things I've never seen before. I got my HV probe, just haven't tested the TV with it yet. I don't suspect that being a problem though. Focus is right in the center of the pot as well.

I am just hoping this NOS CRT is just being funky and will eventually quit doing that. I just can't explain why it was glowing blue in setup line mode like that with a another snap/blue flash in the neck when I shut it down, other than the fact that vertical deflection is shut down (hence the electron beam being concentrated and extra bright), and there is no luminance/chrominance signal present.
This TV has sentimental value to it, and that's why I really want to get it going again.

I did turn it back on after all this in normal mode, and it did not snap one time at all. Picture came up beautifully, no blue glowing. I am so hoping this CRT is just being weird. I just didn't get to do greyscale (which isn't too far off from the old tube, just a little bit reddish at low light). Drives are dead on. I'm wondering if I should just let it run for several hours, get broken in first.
Last new CRT set I bought was in 1996. It did snap a lot (just not like this TV is doing) for about a couple weeks until it broke in. Then it hardly ever did it after that.

It's late and I'll play with this some more tomorrow.

Because after I perfect the greyscale, convergence and purity, this TV should be ready for semi-daily use like I plan to use it for (retro video gaming and being hooked up to the CATV system and Sanyo Betacord VCR).

Last edited by tv beta guy; 07-25-2012 at 06:42 AM.
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  #23  
Old 07-25-2012, 08:13 AM
ischmidt ischmidt is offline
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FWIW, my parents bought a late 60s Zenith rectangular console in '81 or so that had just had a brand new CRT installed and it snapped intermittently with a brief loss of picture (don't know if there was accompanying neck activity) for at least the first 6 months. The tech they bought it from said it was normal behavior, and the set played fine for a decade after that.
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  #24  
Old 07-25-2012, 08:19 AM
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Quote:
Originally Posted by ischmidt View Post
FWIW, my parents bought a late 60s Zenith rectangular console in '81 or so that had just had a brand new CRT installed and it snapped intermittently with a brief loss of picture (don't know if there was accompanying neck activity) for at least the first 6 months. The tech they bought it from said it was normal behavior, and the set played fine for a decade after that.

That is EXACTLY what this is doing! Well that makes me feel better

The neck activity only occurred in setup line mode... not at all running regularly.


I honestly believe this is the case, and I'm just going to let it run. It has only been ran for 15 minutes total after repairing the relay problem last night. This tube is probably 30+ years old and being powered on for the first time
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  #25  
Old 07-25-2012, 09:49 AM
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Good for you for wanting to keep her going

I hope you can figure out exactly whats up!
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  #26  
Old 07-25-2012, 05:43 PM
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Would be interesting to know the high voltage.
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  #27  
Old 07-25-2012, 06:06 PM
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Quote:
Originally Posted by Reece View Post
Would be interesting to know the high voltage.
Just checked it. 29-30KV, just as it is specified on the label, so that is OK.

It is also completely steady too.

Last edited by tv beta guy; 07-25-2012 at 06:19 PM.
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  #28  
Old 07-25-2012, 06:11 PM
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I caught it when it snapped. There was a bright flash seen through the neck of the tube.

But again, this only occurs when I have HV applied.

But when it does it, it is identical to the symptoms Ischmidt mentioned. And it does it at random.

Otherwise, it is working perfectly.
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  #29  
Old 07-25-2012, 09:09 PM
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Check the CRT socket around the Focus pin area, make sure it's not Carbon Tracked or damaged in any way.
If all is OK I'd probably just let it run and see if it clears up.
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  #30  
Old 07-25-2012, 09:39 PM
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Quote:
Originally Posted by Eric H View Post
Check the CRT socket around the Focus pin area, make sure it's not Carbon Tracked or damaged in any way.
If all is OK I'd probably just let it run and see if it clears up.
CRT socket is indeed clean.

Good news is the TV has been on for 4 hours now. The loud snapping actually quit completely about 2 hours ago. Frequency of it happening slowed down to about once every 10 minutes all the way down to nothing at this point.

I am going to let it run all night now since everything else is in check. Hopefully that will break it in so it quits doing that crap.
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