#61
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very common issue with our older sets.you could tweak the coils but i really wouldnt mess with them too much.can you lessen them with fine tuning?when cable came into vogue in the late 70s,i had to tweak many of these to clear the picture up.many hours twisting and turning.
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#62
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I dont think I could tune it out, not sure but I think I tried that. the fine tuning is very touchy, not sure if its a stripped gear or something else, I never cared for the fine tuning knob inside the channel select knob used on maggies. I will go back in and double check to make sure I have all the tube shields in place. other than this one issue it has one of the best pics of my roundies. It also does NOT have the line pairing issue I am fighting on the sylvania. the deflection boards are idenical as far as the circuit, but for a 80uf (sylvaniia) vs a 50uf( maggie) cathode bypass cap AND a .002 disc cap that bypasses the vert hold control (on the maggie, not on the sylvania). other than that they are the same. The sync pulse output has a different resistor value (39k maggie, 220k sylvania) to ground. Perhaps attenuating the sync pulse more in the maggie. the both have VDR's on the plate return circuit of the multivibrator, I have a replacement on the way for the sylvania on the outside chance that somehow that is causing my pairing issues. I hope to get the sylvania in the same room as the maggie and do some side by side comparisons. I may do the .002 bypass on the vert hold just to see if it makes any difference. I just checked the ctc-16 also has a .0022 cap bypassing the vert hold pot...
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#63
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tried the fine tuning, you have to de tune so far out to lose the ghost that all color is gone and fine detail it gone as well.
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#64
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here are some more screen shots, its not too noticiable
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#65
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I'd call it good, personally.
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Evolution... |
Audiokarma |
#66
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I tried a new 3rd IF no change. it does not have a shield over the 3 IF, and the tube socket did not seem to have a ground contract, so I assume that is correct. Put one on it anyway, no change. I did not try 1st or 2nd IF tubes yet. Will give that a try, if that does not do it I will just call it ok for now. Oh also tried the video amp (6GH8) with a couple others inclding a 6EA8, it has a shield which was in place, again no change.
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#67
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A ghost that is that clearly defined, it seems to me, must be delay line related. Rather than the line itself, I would check the resistors and any fixed coils associated with the delay line, especially on the output end.
Edit - also check grounds in the video section |
#68
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roger that, will check out around the output of the delay line.
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#69
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there is a 1800 ohm 5% right after the delay line (back thru a coil then the plate circuit B+ of the 2nd video amp. there is also a 2200ohm resistor across a peaking coil after the coupling cap from the delay line that goes to the grid of the video out, will check that one as well (prob did not check before since it was in P with the coil so will have to take out of circuit to check, same with the 1800 ohm (will have to take out of circuit, will prob just replace both).
Question, do those need to be carbon comp resistors? or will metal film be ok? (the post delay line and the one across the peaking coil). |
#70
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Quote:
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Audiokarma |
#71
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Quote:
oc |
#72
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I will flag the alignment tool and give that a try if the before mentioned delay line parts make no change.
I have a 1076 that I could also use by injecting at the video out and work back, just have not bothered to get it out. |
#73
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Quote:
Two simple checks that you might do prior to twisting coils: Back in the pre-Cable era, before grounded feed lines, the tuner balun coils often failed. You might verify the continuity of them. An open antenna-side coil will often work quite well, but it may produce a ghost. Also, I presume that this set has an FM radio. Many console FM radios offered the option of an internal antenna for local reception, plus a jumper to connect to the VHF TV antenna for fringe reception. I've seen set owners forget to disable the internal FM antenna when using an external antenna and this can also create a single negative picture ghost. Jas. |
#74
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ant not connected, using a 300/75 matching transformer to connect from cable from converter box to set. I will check the balun next time I pull it out for the other stuff.
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#75
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well the 1800 5% resistor of the back of the delay line had indeed drifted, was 2200, I had high hopes, replace it, still there, maybe a bit better but hard to say, prob me just wanting to thing it did something. there is a peaking coil after the delay line, but its got built in resistor so I cant test the resistor (one of those sqaure types with the resistor on the top, covered up.
The only thing I can think to do next is to get a good hard patter, like vert bars from the pattern generator, and see if I can see the ghost on the scope, then signal trace to see if I can find where it comes in. while I had it out I decided to check the horz current, was only 175ma and that was at full line voltage. There was a top for 120vac and 128vac on an exposed term strip, for fun I tried 128vac, could not get the full raster, so put it back. 175ma is plenty good anyway. Maybe my HOT is getting weak. and a new problem the vert has intermittant shakes (pic will be fine then just dims slightly and gets shaky) tapped around could not find any tubes. I was even thinking maybe the HV (boost voltage used for the vert). reseated the vert tube nothing. I am thinking of HV only because of the funny dimming that takes place when its shaking. will put the hv meter on it and see. the spells last a few seconds then stop for a short time then a few seconds... did not clear up after warming up for 30min. this is new... |
Audiokarma |
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