#16
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HV Regulator tubes use lead-impregnated glass to minimize X-ray emission. They darken with use.
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#17
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I think people have posted before that the version B & C of those tubes are darkened
with a coating to help contain some of the x-rays they can produce. With 14KV and the reg tube removed, that means its caused somewhere else. Be sure the HV rectifier is good. Then check for the Possibility of problems in the horiz output drive, or in the flyback. With good width is may be in the flyback. A good place to start is the voltages around the H output tube. Also be sure to check that the flyback is not getting too hot while on, check bias voltage on H output, and cathode current.... I think a number of people here have been on that street before..... .
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Yes you can call me "Squirrel boy" Last edited by Username1; 10-09-2015 at 05:46 PM. |
#18
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oh yea forgot the HV rectifier.
with poor HV (with CRT unplugged) the SOP is to replace the Horz out,Damper,shunt and HV rectifier with KNOWN good tubes. You cant go by tube testers. if those four make no difference the check the Horz out tube pin voltages. This assume of course you have checked the B+ to know the power supply is ok. |
#19
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there is one item worth mentioning, beginning I think on the CTC-15 there was an additional HV hold down circuit added. It works by take the rectified neg voltage from the blanker tube and feeding it back to the grid of the horz out thru a voltage divider. The Idea was if the HV shot up too high this hold down (the blanker got its voltage from the fly) voltage would bias the grid of the horz out more neg, cutting off the tube.
You can tell this when the grid of the horz out is TOO neg. esp if you have a scope and the wave form of the drive signal is normal (compared the neg reading at the grid). what happens is the voltage divider (390k again IIRC) resistor on the chroma board loses its ground thru a very thin trace that runs right along the side of the board right by the HO tube. the trace cracks, the voltage divider no longer divides, and voila you get TOO much hold down. a simple test is to use the resistance charts for the blanker tube. if the grid resistance is too high its prob the crack in the board. |
#20
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Okay. I got things to check then. I'll report back on my findings as I go along. I am out of town for the weekend so I will report back when I start to poke at this set again.
I'm really really hoping the flyback it self isn't bad. |
Audiokarma |
#21
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The part I'm not understanding is; The picture is very bright, and I can turn the brightness up all the way and the screen doesn't bloom or go out of focus. In fact the focus is quite good.
When I play with the controls on the front, or change the channel, vertical conks out for a second or two before it pops back in. It struggles to hold vertical control as well. And while bright, the picture does remain quite yellow. I wonder if my HV probe is just junk? Perhaps the problems are in the vertical section? Horizontal width is still good. And I can get a very sound horizontal lock. I've swapped the tubes around a couple times with good ones, and still no improvements. |
#22
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Would a stone cold dead 1v2 focus rectifier cause the issues the set is suffering from?
I tried to test it today, nothing glows inside, and it is fully dead according to the tester. I can't get anything out of it. |
#23
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It actually had a 2AV2 in the socket. I still can get nothing from it on the tester with the correct filament voltage. It at least glows but does nothing.
I can get the needle to show something with the 3A3 and the other high voltage rectifiers, but this one shows nothing. Not even a little twitch. I also don't think the socket has been modified at all to make a 2AV2 work. |
#24
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1) bad focus rectifier gives bad focus !
2) your pix bright, full width, does not bloom. The hoz osc, out, damper, rectifier, focus rectifier, HV reg are all good. Your meter is NG, try it on another set. 3) arcing at the HV rect socket usually the cup. Other 2 wires are the filament & wrap around the FBT core. ALL the wires are at full HV potential. & can arc anywheres. 4) Try a "by the book" grey scale set-up. then turn you attn to the 6GU7 area of the set. Watch for dried up wires, they were common even 45 yrs ago. 5) put up a few screen shots that show people & colorful scenes. A pattern is fine but a real scene shows more. 6) the old pixs looked AWESOME so unless the jug has aged fast & it happens, you will have a great set. 7) so you have 3 problems. Vert, arc & poor color. You should get a first generation Sams for this set. 73 Zeno |
#25
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Quote:
Then I will set it on fire, and throw it off a bridge. |
Audiokarma |
#26
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Don't set it on fire and throw it off a bridge. I can PROMISE you it won't fix the problem.
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#27
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When you set it on fire and make it go off a bridge, do it in a cool way ! Put wheels on
it, pull it with a rope, make it crash into another set, set an explosion at impact, then have the console go up a ramp, hidden by the smaller tv, explode at the top of the ramp, spin in the air once or twice hit the ground & slide then go off the end of a bridge, crash on the shore next to the water, and then explode again ! That would be Hollywood Cool ! ! Yah....... Oh, don't forget to film it from several directions, splice it into a really good reel, and put it on youtube ! ! Yah...... And post a link to it too..... ! ! .
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Yes you can call me "Squirrel boy" Last edited by Username1; 10-13-2015 at 05:47 PM. |
#28
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Or just give it to me. I'll go buy you a BPC set if you want to throw something off a bridge and whatnot.
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#29
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Explode it and crash it off a bridge ! Don't tell TUD1 till it's over.....SShhhhhh......
.
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Yes you can call me "Squirrel boy" |
#30
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Quote:
A bad focus rect. tube will cause bad focus. One thing you could do while you wait is go to Radio Snack (if one still exists near you) and get 4 of the 1.5KV diodes they sell, and string those in series as a SS focus rect......IIRC roundy focus voltage is ~4100V so 6KV worth of diodes should be able to take it....Maybe add a 5th or 6th for good measure.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
Audiokarma |
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