#16
|
|||
|
|||
Last IF tube. At least eliminate it as a possibility. It can test 'Good' on a tester and still cause ringing. Subbing is the only way to tell. Seen this issue over and over back in the day. Always the last IF. Across multiple brands of color sets.
|
#17
|
||||
|
||||
But I thought the last IF was eliminated by the fact the ghost did not change with changes to the fine tuning?
|
#18
|
||||
|
||||
I tried two tested, 3rd stage IF tubes. No luck.
|
#19
|
|||
|
|||
Quote:
Since VA561 has now subbed it a couple of times, that pretty well eliminates it. |
#20
|
||||
|
||||
Have you considered having the RF/IF stages exorcised?
__________________
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 |
#21
|
||||
|
||||
yeah, I think thats the next step! The same person(s) who devised the most evil device ever made (the convergence board), has possesed the rest of the tv!
|
#22
|
||||
|
||||
hi miniman82 the detector cristal that you is the mentioned is cr302 pix detector on the if schematic board, or any other and if... any suggestions. the other detector in the if board is the sound one. are both the same?
|
#23
|
||||
|
||||
I don't recall which is which, I haven't owned a CTC-9 for some years now. But I can tell you that the type of crystal does matter, if you don't want problems I suggest that you find a good testing original replacement or equivalent. Modern (silicon) diodes will have the wrong capacitance which throws off the last IF stage tuning, and they forward bias at different voltages. If memory serves the crystal one forward biased at around .223 volts, where nearly all modern silicon diodes will be at or above .5 vdc. I scavenge replacements from other sets or swap meets.
__________________
Evolution... |
#24
|
||||
|
||||
It's the video ghost tube...... 3GH8A......
.
__________________
Yes you can call me "Squirrel boy" |
#25
|
|||
|
|||
With all of the posts, I still say it's caused by a bad delay line. Most likely it has a turn of wire inside the delay line that is shorted causing the ringing. You can do a real simple check. The delay line as you probably know is a long hollow cardboard tube soldered on the back side of the chassis, kind of towards the upper middle. It has 3 leads on it. One of them goes to ground. The other 2 is the video signal in and out. Back out the chassis far enough to keep it connected, and throw a clip lead across the input and output leads (wires) on the delay line. No need to disconnect them. The leads will be on opposite ends. Don't worry about disconnecting anything. Leave the ground wire alone. I can almost bet that the ghosting (ringing) problem will be gone, but you will notice the color will be displaced from the Y (black and white) signal. Attached is a picture of the underside of a CTC9. The long yellow tube (stick) is the delay line.
|
Audiokarma |
#26
|
||||
|
||||
thanks miniman82
|
#27
|
||||
|
||||
Make sure you don't a broken ground on the IF cable from the tuner, and check grounds on the IF board.
__________________
[IMG] |
#28
|
||||
|
||||
Not saying it can't be a delay line, I just find it hard to believe. I've had a lot of sets, never had an issue with that part. Incorrect termination can also cause issues, and the resistors are easy to check.
__________________
Evolution... |
#29
|
|||
|
|||
I don't recall many delay actual delay line problems period. The few I have encountered have been open lines that caused only chroma to be displayed. the ones that were shorted caused poor color fit. Not ghosting. Of course this is based on servicing them in the 70''s and now delay lines could be a problem. If it is in the delay line circuit I would suspect an impedience mismatch at one end. Check the terminating circuits. I have also seen this problem caused by poor IF response. I know the dreaded alignment. Could be a bad cap in the IF. Especially if they are hidden in the IF can. Bad soldering of the board to all the ground stakes can also cause it. I would reflow them and not depend on seeing a crack. Just do it. Same with all the boards. Alignment is really not that bad if you have access to the equipment. Even if you make no adjustments an alignment hookup could tell you a great deal about how well the IF is preforming. Also don't overlook any peaking coils in the video circuits.
good Luck. |
#30
|
||||
|
||||
I'm slated to pop on by tomorrow anyway, it's probably something simple.
__________________
Evolution... |
Audiokarma |
Thread Tools | |
Display Modes | |
|
|