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#46
12-08-2009, 08:54 PM
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on what I belive was the low pass filter (a resistor cap to ground cap to grid of osc) from the sync separater/phase inverter I found a cap that was a .01 and per the schematic it was suppose to be a .002 (verified that on two other sets with the same chassis). It did not look original. I replaced it, still have the interlace instability (it jumps in and out). I put a scope on it and checked the input to the vert osc one check has it with the osc tube in and the other with it out (brt turned down). in both cases the wave seemed to move around on the scope, not so on the other set that is good. with the tube pulled you can see the sync pulse, on the good set it looks like the sams on the bad set the low part of the wave it thick, if I speed up the scan I can clearly see a hi freq wave in it. both sets have this, but on the bad set it in prob 4 times as big. I will post some pic later to try and make it clear what I am saying. the other scope readings of the sync sep and agc keying tubes were in conclusive, did not look anything like the sams, but neither did the working set. I will have to go back and take better notes, one ready I got was about a 3 order magnitude higher on the non working set than the working set.
checked it: that was on the sync phase inverter grid, the non working set was much higher amplitude than the working set. 
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#48
12-10-2009, 01:44 PM
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I will snap one later. I may be making a moutain out of mole hill. I tried some OTA pics using a DTV converter (had been using a dvd), and it did not look too bad. I will take a pic of the good set vs the bad set for comparison.
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#50
12-11-2009, 08:51 AM
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something new (well not new just did not notice before i think) the scan lines at times seem to appear more as dots not lines. it Seems to be related to high contrast video. Considering the speed at which the scan line is being formed, what ever it happening must be at a very high freq. I am wondering if some how the video is getting clipped off? could it be an AGC thing?
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#53
12-11-2009, 11:48 AM
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Cold I be in the IF stages or tuner? Also I have has issues with an RCA spotting waves of dots on the screen and it turned out to be an issue with the horiz afc tube. Even though it tested good I replaced it and problem solved.
__________________
Honey, turn on the tv.. I'm cold!
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#54
12-11-2009, 12:31 PM
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I was advised to check the video at the diode detector, will give that a go.
I got this marker/genrator tool, big box with lights on what looks like a IF wave in the front. I have no idea how to use it, no manual etc... but looks like the thing you need to check/adj alignment. the AFC for the horz on this one is a couple diodes, they were replaced a while ago, I figured the only function was to sync up the horz. I may try some tube swapping in the IF next from a known working set. What bugs me is I was not able to get the effect on the dot/bar generator. I think I may be looking for one of those B&K video analyzers, maybe helpful in chasing these dogs down.
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#55
12-11-2009, 02:06 PM
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Quote:
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#56
12-12-2009, 02:17 AM
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Different sync signals are given between video feed and a generator. I have run into different sync pulses fed from a generator like by BK color/dot/bar generator than that of video feed from a VCR. Possibly some kind of overload?? Try turning down the AGC possibly.
__________________
Honey, turn on the tv.. I'm cold!
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#58
12-12-2009, 08:02 PM
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giving the TV a break, pulled the TT (platter would not spin). the idler wheel had a big flat spot AND a nice divot (where the motor spindle must have been resting for years). The tone arm Ilder was still somewhat pliable, and I was able to work its slight divot out, but the platter ilder divot and flat were a whole nother matter. the rubber was rock hard. I chucked it up in the lathe and took off enough to get down to the bottom of the divot (the flat wa not as deep so it was gone by then). prob took just a bit less than 1/8 total off the diameter. I then found a suitable rubber band (from a broccoli plant) and placed it around the idler wheel. Its prob only at most 1/32" thick but nice tack to it. Tried it out, works great. I also found a MPX on epay so that will be here in a couple days. It's a nicer one (3 tuber) prob need a filter and a single coupling cap (it has a 1uf in there that goes bad). I will put it in and then take another look at the TV.
I am tempted to install a magnavox color TV (tubes of course) that I may be able get locally. the cabinet is shot so it would not be a sin to use it, except for the fact that this would then be a franken set.
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#60
12-13-2009, 05:04 PM
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while messing about with it some more I noticed a horz linearity issue, the left side is wider than the right side, happens in the 1st couple inches. Odd thing is its larger while on another maggie with the same chassis I have a horz lineairity issue but its smaller, while on a 3rd its perfect. Oy...
Since there is no adjustment for horz lineairity, I will start by swapping the tubes from the good set to the bad (I dont think this will do anything, since I think I have done this already) the horz osc, HOT and damper. Next I will check the resistors and caps, again, pretty sure I have already done this. Oh and the one that works has the worst looking flyback of all. reallly really bad, but works fine. Crawl still there, not all the time but its there.
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