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 Post subject: RCA CTC-16 - width adjustment?
PostPosted: Jul Fri 13, 2012 5:03 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 377
Location: moreno valley
I've dusted off my two-speaker floor model ctc16 and put it in one of my mom's house's unused bedrooms, after doing a recap on it about oh 10 years ago, and hooked up a digital OTA tuner to it. Other than having to clean a couple of tube's pins off it still works great. I just wanted a cool old roundie over there that I can watch when I am visiting and get bored : )

BUT I could have *sworn* that when I originally had this set at my house, it had an adjustment for the width, specifically a 3-position switch. Correct or no? I don't know if it's just my brain getting older or what but I can't find any "width" control on the set or on the schematics. If I'm just plain wrong, is there any way to do a direct width adjustment on this set, or am I limited to the rest of the settings like centering, vert height, linearity etc.? Is it possible I was playing with an adjustment other than these and maybe it is labeled as something else and I'm just not associating it with adjusting width? Geez that memory of a 3-pos switch and flipping between the widths sure is strong, I thought maybe it was from another of my few color roundies but I checked and don't see it on them either. Thanks for any info... Frenchy


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Fri 13, 2012 5:49 pm 
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Joined: Aug Mon 16, 2010 6:58 pm
Posts: 171
Location: Madison, WI
Hi Frenchy,

I'm not familiar specifically with the CTC-16, but I know that earlier RCA roundies had different taps on one of the yoke connections for adjusting the width, one being a "dummy" no connection tap. I believe they are the blue wires on the top side of the yoke.

Good luck and enjoy that roundie!

-Clark


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Fri 13, 2012 6:09 pm 
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Joined: May Mon 11, 2009 12:19 am
Posts: 426
Location: LA
The 3 position switch is for crt bias. There is no width, there is a horz and vert centering pot.

Is it too wide or not enough. A common problem is a cracked trace on the edge of the board that causes to much drive and a lack of width on the 16.


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Fri 13, 2012 7:46 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 377
Location: moreno valley
I'll take another look at it this weekend and take my old Heathkit bar/dot generator with me. Picture is filling the whole width of the tube but I'm wondering if it should be overscanning a little more or I'm just being too picky. Faces look skinny to both my mom and myself, but I'll verify it with the generator. Seemed this way 10 years ago too but it was not really that noticeable so I never messed with that issue any further. Would that cracked trace problem cause a more severe lack of width than this? Anyway I'll recheck vert size and linearity too and report back.

I have a ctc10 and 11 that have those adjustable plugs on the yoke.
Thanks... later!


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Fri 13, 2012 8:28 pm 
Member

Joined: May Mon 11, 2009 12:19 am
Posts: 426
Location: LA
It depends on your line voltage and condition of the horizontal tube etc. If you had a strong tube and line voltage say up at 122-125 you would get what you are describing.

There is a 390k resistor off the grid of the 6GU7 blanker tube, the trace goes from that resistor to ground. Check to make sure one side of the 390k is grounded. Its all right on the edge of the board near the horizontal output tube. The trace is on the very edge and runs from that resistor to the stake at the back of the board.


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Sat 14, 2012 9:18 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1444
Location: Manitowoc, WI USA
And... If you are using a DTV converter box, make sure the aspect ratio switch is correctly set! The setting frequently referred to as "anamorphic" can cause distorted images similar to what you are describing.

_________________
We improve things by making them worse...


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Wed 18, 2012 1:23 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 377
Location: moreno valley
With the crosshatch generator today I dialed in all the vertical stuff (size/linearity/centering) better than I had originally, looks like I had the linearity wrong and it was stretching the top half more than the bottom, looks much better now. Digital tuner is set for 'full' so that it doesn't squish the picture in horizontally.

I'm going back there tomorrow and will recheck the horiz linearity before I slap the back cover back on, I think there is a 'horiz effic' screw back there if I need to tweak it. Oh shoot and I forgot to look at the yoke and see if there are those moveable plug settings. Or is it a sure thing that ctc-16s didn't have this available for width adjustment either?


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Wed 18, 2012 2:43 am 
Member

Joined: May Mon 11, 2009 12:19 am
Posts: 426
Location: LA
The linearity coil is used to minimize the horizontal output cathode current. If you tweak it to make the picture wider the set will eat horizontal output tubes and may destroy the flyback.


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Wed 18, 2012 5:21 am 
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Joined: Aug Thu 07, 2008 1:36 pm
Posts: 2264
Location: Orlando
did you check that blanker tube bias resistor that Shango mentioned? That will make the entire HV weak including sweep, it show up as too neg a reading on the horz output tube control grid (the bias is coming from the blanker tube, its there to prevent runaway HV incase the shunt tube is not working properly). If that resistor he mentioned goes up in value or the circuit on the pcb cracks due to heat from the HOT, the voltage divider network is upset and the bias from the blanker is too negative, resulting in a horz out tube that is partly cut off. Don't assume that just because you get a negative reading on the grid of the HOT that everything is ok. You need to confirm that the drive is correct AND the bias adj from that blanker tube is correct.


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 Post subject: Re: RCA CTC-16 - width adjustment?
PostPosted: Jul Thu 19, 2012 6:52 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 377
Location: moreno valley
OK I didn't mess with the horiz lin pot since I didn't really see anything wacky in the crosshatch pattern as far as horiz lin. For now it looks good, width doesn't look overblown at all when I go thru the range of the horiz hold knob. But I'll check the voltage as per that adjustment to be safe.


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