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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Oct Thu 26, 2017 6:18 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Powered up the set with all tubes installed and the CRT. All the filaments light, but no raster after several minutes. Did the screwdriver test on the 1B3GT and there is barely any spark. It only arcs maybe a millimeter, so I know I have a problem with low voltage here. Not sure how to proceed, but would really appreciate some suggestions. I did check the 5U4G for voltage without the CRT at pin 8 and got 310 volts which is high.

Thanks!


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Sun 12, 2017 3:06 am 
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Posts: 2800
Location: Hayward, California USA
I hope you are still checking for messages here. I do not see a note that you checked or replaced off-value resistors, so there could be some bad ones. One other thing to do is to move the ion trap around the CRT neck to find the "sweet spot" where the raster would appear and be its brightest. Let us know if you have any questions about that procedure.

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Quote: (Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did.


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Sun 12, 2017 4:05 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Hi ChrisW6ATV,

I have been checking for messages but have seen no responses to my questions. I am guessing that there are no simple answers. I have replaced a few of the large 2 and 3 watt resistors. I tried a few new 6SN7GT for valve # 18 the horizontal oscillator. Now I am seeing a arcing from the plate caps of the 6GB6G and the 1B3GT, when touching them with a screwdriver. I can draw at least a 1/2" arc from the 1B3.

I have tried moving the ion trap around but still no raster. Perhaps I have put it in wrong. There is an arrow printed on it which I thought should point to the front of the set.

I checked the flyback with my ohmmeter and the readings I get are all good except 1 to 3 reads a bit low 319 ohms instead of 341. Center tap is spot on at 172 ohms. These are the primary windings. The secondaries are all spot on except for the high voltage winding which reads .2 ohms instead of 0. I only see a few turns of this heavy thick wire here and the insulation looks good but it's possible there may be a small crack in it somewhere. The 1 meg resistor under the 1B3 socket is spot on. Plastic insulators on the high voltage cage look somewhat melted and the anode wire looks discolored where it passes through.

I checked the yoke for resistance and think there may be a problem here. I get 13.5 ohms for section a which is spot on, and 6.5 ohms for section b. Parts list shows 65 ohms! Could this be a misprint? The windings inside the yoke are covered with a milky film of some sort as is much of the inside of the cabinet. I think perhaps someone used too much of an aerosol type cleaner on the cabinet and it got inside.

I will be getting the CRT tube tested later this week.

I hope to be able to post some pictures later in the week.

Thanks everyone!


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Sun 12, 2017 5:39 pm 
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Joined: Dec Thu 06, 2007 11:54 pm
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Location: Hayward, California USA
To me, the half-inch arc from the 1B3 means you have a good amount of high voltage. That likely means that the horizontal circuits are working reasonably well overall, too.

You should check the voltages (not resistances) on the pins of the CRT socket when the set is on and compare them to the schematic diagram or charts. Check if one or more of the voltages changes as you turn the brightness control from end to end and make notes of what you get, also.

The arrow on the ion trap should point to the front as you thought, and you should try it in all positions of the CRT neck front to back and all around with the brightness turned all the way up. You could also turn it backward and try again if you have no success in its normal direction, but put it back if you still do not get any light on the screen.

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Quote: (Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did.


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 13, 2017 3:15 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Thank you ChrisW6ATV!

After considerable fiddling with the ion trap I got a nice bright raster easily seen in a well light room! I guess the next step would be to hook it up to a dvd player. I am not interested in using cable, only watching movies, so I would need a digital to analog converter? Is there anything inexpensive and easy to hook up that is readily available?


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 13, 2017 6:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5152
Location: Woodinville, WA USA
If your DVD player has an output terminal labeled "RF Out," then all you need to hook up is an inexpensive antenna matching transformer:

https://www.ebay.com/sch/i.html?_from=R ... 5&_sacat=0

If you search for "antenna matching transformer," you'll find many for sale, from various suppliers.

Attach a coaxial cable from the DVD player's RF Out terminal. Attach the matching transformer to the end of the cable. Screw the transformer's two spade terminals to the antenna terminals in the back of your old TV.

If your DVD player only has A/V outputs (two audio jacks and one video jack), then you can get an inexpensive RF modulator to attach between those outputs and your TV:

https://www.ebay.com/sch/i.html?_odkw=1 ... acat=32852

Use three wires to connect your DVD player output to the RF modulator A/V inputs. The RF modulator will have an output terminal labeled "RF Out" or "TV Out." Connect that to your TV using a coaxial cable and antenna matching transformer as described earlier.

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Tue 14, 2017 4:12 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Thank you Phil! I have ordered the antenna matching transformer and the RF modulator. Should have them by end of week.


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Wed 15, 2017 4:25 pm 
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Joined: Dec Thu 06, 2007 11:54 pm
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Location: Hayward, California USA
stuben wrote:
Thank you ChrisW6ATV!

After considerable fiddling with the ion trap I got a nice bright raster easily seen in a well light room!

You are welcome. I am happy to hear of your success. Your next one will be much easier, I am sure. (-:

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Quote: (Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did.


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Wed 15, 2017 4:40 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Already got my eye on another set! National TV-7W : http://www.earlytelevision.org/national_tv-7w.html


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Wed 15, 2017 6:49 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5152
Location: Woodinville, WA USA
Those Nationals are nice TVs. This article describes how I restored mine:

https://antiqueradio.org/NationalTV-7W.htm

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 20, 2017 12:30 am 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Attachment:
9945a1210f2a28af1511133426.jpg
9945a1210f2a28af1511133426.jpg [ 32.31 KiB | Viewed 315 times ]


I hooked the set up to the DVD player and everything seems to be working fine!
The audio is still a bit noisy, but not too bad.
Thanks for all your help!!!!!!!!


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 20, 2017 1:51 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Sorry about the small image! I have so much trouble posting pictures and can't figure out how some of you manage to post such large detailed images. If someone here could point me in the right direction I would greatly appreciate it,

Thanks!


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 20, 2017 5:49 pm 
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Joined: Mar Sun 01, 2009 10:27 pm
Posts: 4246
Location: Ann Arbor, MI
stuben wrote:
Sorry about the small image! I have so much trouble posting pictures and can't figure out how some of you manage to post such large detailed images. If someone here could point me in the right direction I would greatly appreciate it,

Thanks!

Check the thread at the top of the Clubhouse forum about posting pictures.

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Tom


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 Post subject: Re: RCA Victor 8-T-241 TV
PostPosted: Nov Mon 20, 2017 7:02 pm 
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Joined: Oct Thu 23, 2014 5:15 pm
Posts: 46
Thanks Tom! Will do!


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