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#16
11-26-2005, 11:24 PM
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I changed that tube socket, all the electrolytics, etc. The tv more or less works good now.
I moved the filament wiring like I said I was going to do earlier, putting the 6K6 on the 24v trans, and it turned out only to get around 3.5 volts and the sound was to low, so I put that resistor back in and put the 6K6 back on the 6v trans. None of the local electronics shops had the 6kv caps, so the HV filter cap is still one of the old ones, and for the vert. sweep coupling I am using ceramic caps in parallel. I have to readjust the vert. hold whenever I change the channel. The 7jp4 is weak, the picture is clear, but on the dim side, and if I turn the brightness up I get the vert. retrace lines. Last edited by Adam; 11-27-2005 at 04:04 AM. 
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#17
11-26-2005, 11:42 PM
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Nice job getting the set working. The big scary Red HV filter was a replacement. The original was a paper wax cap.
The 6kv caps are near impossible to find. Mouser electronics I believe has them. You could always put a couple of .002mfd and a .001 in parallel for the .005 cap. THat seemed to work fine for my other TS-14 chassis.
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Jordan
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#19
11-28-2005, 05:38 AM
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I just checked it out, they do have these 6kv caps, up to .0047mfd. It is good to know that these are still available. The 7JP4 is so weak that I have to watch it in the dark, so I certainly won't be using it much, mainly just to preserve the crt as long as I can, so I won't have to change these right away. Although, I am happy to have a set this old that works at all, it is the oldest working set I have, and the only electrostatic one.
Last edited by Adam; 11-28-2005 at 07:42 AM.
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#20
12-04-2005, 05:51 AM
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For about 2 days last week I became very worried, as my computer kept telling me this place didn't exist anymore. Now I am very relieved to find out it was only due to this server change. Anyway, during that time I was looking for other old TV forums, as I can't stop reading these. On one of these, I found an interesting modification to be made to one of these early Motorolas to remove retrace lines. It works like this: take C139 (which goes from pin 5 of the vert. out tube to ground, and connect a 220K resistor inbetween the cap. and ground. Then take the wire going from the first grid of the 7JP4 to ground and instead connect it between that cap. and the 220K resistor. It was claimed that this would not only take out the retrace lines on normal tv channels, but also take out those ones you get when watching one of those awful DVDs with the junk in the first few lines of the picture. I tried it and it works. I thought people here might benefit from this as well. Does anybody here understand exactly how this works? Is it something limited to this set, or to electrostatic sets? Could a similar modification be made to later model electromagnetic tube sets or mabye even tube color sets? I would really like to be able to watch these DVDs without the retrace lines on an old tube color set.
Last edited by Adam; 09-13-2009 at 10:38 AM.
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#22
12-07-2005, 11:48 PM
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Some pictures. I don't have the proper equipment to take a picture of the TV working. But you can see alot of the modifications I have been talking about in the chassis pics.
Last edited by Adam; 09-13-2009 at 10:38 AM.
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#23
12-08-2005, 06:18 AM
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One thing I've noticed about virtually all of the little 7" electrostatic sets I've seen is that NONE of 'em has a very good picture-nowhere near in comparison to some of the pictures produced by the first roundies I've seen here. It also seems as if the 7" sets are working right at the very edge of what they're capable of doing-1 more volt on this resistor or that cap, & the whole shebang will self-destruct. Maybe they weren't like that, 60 yrs ago when they were new, but I've got radios from the twenties & thirties that don't seem to be bothered by being run. Is this just me ?-Sandy G.
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Benevolent Despot
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#24
12-08-2005, 11:24 AM
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I have a 1949 Motorola 9VT1 with a TS-18 chassis and the 8BP4 picture tube. It works quite well and doesn't seem to be bothered by being on for hours at a time. I have noticed, though, that radios are far more reliable than tube TVs and I suspect it is because the TV has more parts operating at higher voltages and component values are more critical. I might just try that mod to remove the retrace lines. they are really bad on the channels around here. When I show a DVD through an RF modulator, I get no retrace lines.
Quote:
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Just look at those channels whiz on by. - Fred Sanford
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#25
12-08-2005, 07:52 PM
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The only real problem on mine is that the 7JP4 is so weak. I think even more than when I first got it to work. That modification against the retrace lines really helped the picture on mine. (Some DVDs cause this problem while others don't.) The vertical is not exceptionally stable, I have to readjust it when I change the channel, and the picture sometimes 'shakes' a bit. But somewhere (I think here) I read someone saying that this problem was caused by having two ceramic caps in parallel as a replacement for those 6kv caps like I have.
I have had mixed experiences with the radios from the same time. I have a '48 Stromberg-Carlson console radio, I bought it at an estate sale with all the tubes missing. I put tubes in it and it is the best working AM radio I have. I never even changed a single capacitor. Sometimes at night I can pick up AM all the way from Albequerque NM, with only the antenna in the set. It also has that old FM band 42-50Mhz? I think. But I also have a '49 Capehart console radio that was my great-grandmother's. A few years ago it burned out an output trans. After I replaced it, I never could get it to work again. Replaced every tube and capacitor in that thing, and all I could get was really low volume FM, only at the top of the dial, and no AM at all. Last edited by Adam; 12-08-2005 at 08:45 PM.
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#26
12-09-2005, 09:03 AM
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I originally used ceramic caps in mine and had vertical problems. Even now that I have all tubular caps in there, I still have to adjust the vertical hold after it has been on for a few minutes. I think it is just a characteristic of this type of set. Hawkeye can rebuild 7JP4s for $250 IIRC. It might be worth thinking about if you plan to keep and use the set regularly.
(QUOTE) The vertical is not exceptionally stable, I have to readjust it when I change the channel, and the picture sometimes 'shakes' a bit. But somewhere (I think here) I read someone saying that this problem was caused by having two ceramic caps in parallel as a replacement for those 6kv caps like I have.
__________________
Just look at those channels whiz on by. - Fred Sanford
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#27
12-11-2005, 10:06 AM
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I think you might be right about the vertical on these sets. I found some 35kv .005mfd tubular film caps and an electronics surplus store yesterday and tried them and it wasn't much of an improvement. The vertical is not as 'shaky', but I still have to adjust the hold most of the time I change the channel.
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#28
12-11-2005, 10:36 AM
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Quote:
look for weak sync.
__________________
i collect and restore vintage radio's,tv's,and ham gear. email for more info
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#29
01-15-2006, 11:37 PM
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I changed out the ceramic caps in the horiz. and changed that big red oil .01 HV filter with one of those .005 ones I have, and it helped the veritcal be more stable. Why, I don't know. The CRT is still too weak to use this on a regular basis though.
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