Restoring a 1963 Admiral ctc-12 clone

[Tubejunke]

Originally Posted by old_coot88

You're speakin' of the Simpson 260, right? That's the only meter i ever used for general servicing for 30+ years (except for the rare occasion when a VTVM was needed for probing some high impedance circuit).

You might be able to run red lights and stop signs for a while, too. I would never use a digital (don't even own one) for anything but pure DC, clean sinewave AC, or ohms.

I like the way you think!

I would like to learn more about exactly what a VTVM can do that no others can do, or do as well. I have a Simpson VTVM and a huge bench model Hickok.

[old_coot88]

Originally Posted by kramden66

old coot any idea whats causing the ghost in my set ?
mike

No idea. But for a start, i'd check all the peaking coils 'downstream' from the video detector thru the video output. They're little single-winding coils that normally measure just a few ohms or less. You don't have to disconnect them to measure, since the ohms are so low.

TJ:
A VTVM's main advantage is its very high input impedance. It doesn't impose near as high of a load on a high impedance circuit as the VOM does, thus minimizing loading error. An example of such a circuit is the AVC (automatic volume control) buss in an AM radio.

[kramden66]

I did check the peaking coils and rechecked , they all measure low ohms , nothing above 10 ohms.

[timmy]

did you check any of the caps or resistors within the yoke? may be worth a try.

[old_coot88]

What would the yoke have to do with a ghost or 'ice' in the video?

[timmy]

because i had a simillar problem with a motorola 23 inch color and it turned out to be a resistor. just throwing that out there being no one seems to be able to narrow down this problem he has with that set. there could be a convergence issue there are caps and resistors there as well.

[kramden66]

Timmy I think old coot could answer this - the convergence is lining up the red blue and green , this issue seems to be video or IF related and looks like its in the black and white portion of the image , am I right or should I look at convergence ? my next step since I've checked everything else would be to check the video areas and those resistor looking capacitors , I don't know what else to check , they are all low values like 10pf 20pf 6pf etc

mike

[old_coot88]

Originally Posted by kramden66

...the convergence is lining up the red blue and green , this issue seems to be video or IF related and looks like its in the black and white portion of the image , am I right or should I look at convergence ?

From the pics you posted of the "NBC" symbol display, the "ice" problem appears to be in the luma (video) or video IF chain. Definitely not convergence or yoke related.
Assuming the problem's already determined to be not tube related, troubleshooting just about demands a signal generator (like the B&K 1076 Analyst). Working backward from the vid out stage, inject signal stage by stage until the problem's isolated.