My Brand New CTC-7!

[Phil Nelson]

Do you mean you have no hint of color no matter where you turn the fine tuning knob?

The adjustment procedure for the oscillator is described in pages 36-37 of the RCA factory manual, but if you don't see any color at all -- maybe rolling "rainbow" color bars, for instance -- that procedure may not get you anywhere. (In that event, I would start by doing resistance and voltage checks on the 3.58-MHz oscillator tube to get some clue whether the oscillator is capable of running at all.)

To do the adjustments described in that procedure, you need non-metallic tools -- a screwdriver for L704 and a "diddle stick" with an Allen-like head for the other adjusters mentioned. You may find such tools listed as "TV alignment tools" on eBay.

Phil Nelson

[SwizzyMan]

I will get rolling rainbows on the color bar pattern but only when I turn the fine tuning all the way clockwise.

[SwizzyMan]

Woah all of that looks complicated... Can I do this without a vtvm?

[SwizzyMan]

cant even get a rolling rainbow anymore. I am so confused.

[miniman82]

Diddle sticks, they are a plastic allen sort of thing. You can't use a metal tool, because it screws with the tuning of the core when you attempt adjustments. You can buy a whole set of them real cheap on eBay, just look for TV servicing tools.

[SwizzyMan]

OK. Where is the reactance grid and how do I ground it?

[MRX37]

Originally Posted by miniman82

Diddle sticks, they are a plastic allen sort of thing. You can't use a metal tool, because it screws with the tuning of the core when you attempt adjustments.

I learned this the hard way trying to tune convergence on an RCA delta gun set and by the time I figured out that you needed a non metal tool, I had disintegrated one of the tuning slugs.

[SwizzyMan]

Diddle sticks as in these? http://www.ebay.com/itm/Radio-TV-Ali...item1c55dfe0af

[miniman82]

Something like this should suffice:

http://pages.ebay.com/link/?nav=item...obalID=EBAY-US


Ought to get one for myself, my diddle sticks are pretty wore out...

[SwizzyMan]

I will try and pick that one up. If I don't win is there anything else listed that will work?

[WISCOJIM]

Originally Posted by miniman82

Follow what the manual says, usually it goes something like this:

Ground the reactance tube grid with a color image on screen, and adjust the local oscillator coil till a rainbow pattern just floats by. Remove the ground from the grid, and color should snap right in.

http://antiqueradios.com/forums/view...47598#p2347598

.

[Phil Nelson]

Originally Posted by SwizzyMan

OK. Where is the reactance grid and how do I ground it?

Look at the description of Step 4 and the photo on page 36 of the RCA factory manual (I provided a link to that manual above). Step 4 tells you to ground the reactance tube input at the junction of C726/R743. If you look at the schematic on page 50 of the manual, find that junction and then follow the connection to pin 9 of V707-A, the 6U8A reactance control tube. Grounding the point shown in the manual effectively grounds the input grid of the reactance tube.

Step 4 also tells you to ground terminal D of transformer T701, also shown in the photo on page 36.

You can ground these points with two clip leads -- wires with an alligator clip on each end.

After grounding those two points, you can try (gently!) adjusting the reactance coil L704, also shown in the photo. If you don't have a plastic screwdriver, you can make a tiny adjustment using a metal screwdriver and then pull it out and hold it at least a foot away from the coil. See any difference? You want to slow the rolling of the color bars. This is a cowboy way to do it -- the bars may go nuts when the screwdriver is in the coil and your body capacitance affects the circuit. But when you pull it out and step back, you should be able to tell if your adjustment made any difference.

If adjusting in one direction makes the rolling faster, try adjusting in the opposite direction. The ideal is for the bars to be static -- floating without any roll -- but a very slow roll is better than a fast one.

If you get the bars to stop rolling, remove the temporary ground connections and see what the picture looks like.

If the cowboy adjustment doesn't work, I would do careful checks of resistances and voltages on V707, which acts as both the oscillator and the reactance tube.

Phil Nelson

[SwizzyMan]

Ok just won the auction for those alignment tools. I will take a stab at it when they arrive!

[old_coot88]

Phil,
Not to be a fuddyduddy but I would heartily recommend against sticking anything into an adjustment slug other than the prescribed tool. The slugs are sooo fragile and easy to bust.

[Phil Nelson]

Good point. They made special tools for a reason (sometimes more than one).

Phil Nelson