My Brand New CTC-7!

[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

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[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?

[SwizzyMan]

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

[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.

[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.

[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?

[dtvmcdonald]

It could be that the owner is over his head in this one. Or it could be a problem
insolvable by logic, even by a real hot-shot on the spot with good test equipment.

I have good test equipment and experience ... I had the same problem (intermittent
horizontal sync) in my CT100 --- its only real difficulty after a recap. I tried for weeks
to figure it out with a two channel scope on various pairs of places and never
succeeded, but did prove it was the oscillator itself.
It was only cured by a total, all at once, re-resistor of the horizontal oscillator.
No removed resistor tested bad either at room temp or heated with a heat gun
(at low voltage). All solder joints had previous been resoldered. So it was a
resistor changing, instantaneously, from one value to another, at voltage.

I suggest, if he can use a scope, first measure the waveforms in various places
in the sync circuit, when its working. Then first attach the scope to the plate of
the 2nd video amp and measure the waveform when the set is in sync.
Leave it attached there. Attach a zero to minus 10 or so volt bias box to pins
F and G of the PW400 board (AGC amp) and adjust so that you get the correct
signal on the scope. Leave it there and start measuring waveforms in places in the
sync circuit and the horizontal oscillator with it in or out of sync. Be patient!

That's just about all you can do to pinpoint problems unless somebody else has a
better suggestion. That's how I proved my problem was the horizontal oscillator.
Ideally this would be done with the horizontal output tube removed, as described
on p. 14 of the service notes (with schematic, at ETF) ... BUT! ... that requires
a 100W 1500 ohm resistor.

[SwizzyMan]

Here is a video of what is currently happening.https://www.youtube.com/watch?v=937D...ature=youtu.be Note after about 3 minutes or so the horizontal becomes a lot more stable.

[dtvmcdonald]

Originally Posted by SwizzyMan

Here is a video of what is currently happening. Note after about 3 minutes or so the horizontal becomes a lot more stable.

No attachment or pointer to one.

Edit 15 seconds later: it appeared!

[SwizzyMan]

Sorry about that

[SwizzyMan]

OK after about a 5 minute warm up period the horizontal hold becomes acceptable but not that great it will stay locked but will bend and swerve on some certain pictures. I just need color now the horizontal is good enough for me now. I just want color.