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#46
05-24-2023, 08:10 AM
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They used to sell a kit that had a special cleaner and lube, plus a foam pad that went on the cover with the lube. After a while, the pad deteriorated and cruded up the tuner more. 
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#47
05-24-2023, 10:11 AM
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Yeah, the tuner was very dirty, it was a bitch to get out because of the silly front screw in system they use that you have some odd key to unscrew.
Even after cleaning the contacts for chan 3, had problems getting a clear pic due to what I believe to be tired/ worn tuner tubes, only after hooking in a 15db rf amp was I able to tune in a clear video w/o snow. Cause as mentioned, it seems that almost every tube is OEM and most likely worn/ tired. I did try a couple of 6GH8As in the V19 socket ( h-blanker / bandpass) that were of unknown state, the first one made no change in the picture at all, the other must have been VERY bad, cause something smoked as soon as it was turned on, but STILL WORKED when the previous tube was put back, will no doubt find what it was when I check resistors, most likely many will be out of tolerance and need to be replaced. Tubes ordered so far, based on what was observed, both tuner tubes, video output tube ( the video was being overpowered by color ) and the R-Y B-Y G-Y compactron, what color there was , is very off balance like one of the Y-amps was weak, though this could be bad resistors, but a 50+ year tube can also do it. As mentioned, C1 is going to be a big pain to replace, C2 C3, are not so bad, but it looks like C1 was put in first, soldered in a very tight area, and then everything else wired in neatly and tightly in layers under it, there is no way to reach the bottom of C1 w/o ripping it all up. What I may end up doing is attacking C1 with a dremel cutting wheel, won't be pretty but should work, cut around the base remove can and guts, work down to attach 3 new caps using solderable base of old C1 while leaving wiring to it under it undisturbed. ( idea anyway ). But for now, gonna start with checking resistors on the chroma / luminance board.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#48
05-24-2023, 01:08 PM
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Another annoying thing with this TV, is that “Instant On” was enabled, most likely for a very long time, which must have cooked the heck out of these poor old tubes.
Also, not seeing full vertical deflection, and linearity is a tad off, also a sign of bad caps and resistors in the sweep PCB.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#49
05-24-2023, 02:10 PM
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I found out why that one 6GH8A made something smoke like it did, I really don't think the getter is supposed to upside down in there like that... it broke off!
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#50
05-24-2023, 10:44 PM
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#51
05-24-2023, 11:28 PM
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i did find what smoked.
http://suzaku.live-evil.org/smoke11.jpg R164 went up in value R165 went down.  both replaced.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#52
05-25-2023, 08:42 AM
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One thing about the PCBs used in this maggie TV, they are much more dense / thick than the ones used in RCA, GE and others I have worked on in the past, example, previously I have been able to take my work light (halogen hand lamp) and point it at the top of the board, and see light through the PCB, along with the shadow of the offending component from the bottom side, but not with this Magnavox :O no light at all gets though the board!
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#53
05-25-2023, 10:16 AM
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#54
05-25-2023, 10:23 AM
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__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#55
05-25-2023, 01:07 PM
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#56
05-25-2023, 01:23 PM
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There was also heat marks on the PCB under these 2 parts already, I suspect they were already on the way out, and putting in the bad tube did not help it! :P
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#57
05-25-2023, 01:40 PM
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#58
05-25-2023, 01:47 PM
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The one thing I do not lile about the T931 (and the T933 as the same design) is that it doesn’t use DC reinsertion, but instead uses partial DC coupling of the DC bias from the video detector. This causes inconsistent black levels, especially for super bright scenes, which cause black crush. I am tempted to add a diode clamper to make brightness more consistent between scenes.
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#59
05-25-2023, 01:50 PM
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Well, all the others in the area seem to check OK, it was most likely being fed by the big 4w resistor on the triode plate P1.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#60
05-25-2023, 03:52 PM
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Yeah, the tuner was very dirty, it was a bitch to get out because of the silly front screw in system they use that you have some odd key to unscrew. >>>>
The screws with 2 holes come out with long needle noses. They also used 2 sizes of inside out nuts. I saw everyone fighting them so called Maggy FS to get part ##'s & ordered 2 sets. I told the techs if they lost them they will build stands for 60 days  BTW many sets had a 'lytic on the conv PCB, causes bad V lin. IIRC this had it ? Zeno
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Linear Mode
