Hi Guys:
I am working on an RCA 17T160A and I have recapped and re-resistored it and its working pretty good but has a strange, to me, problem. The picture looks to be the right size and all but it looks like it is missing every other scan line, is this possible? Anyone have any thoughts on this?
Thanks

Gregb

Sounds like line doubling. Basically the odd lines field and even lines field are scanned over each other due to slight miss timing in the vertical stage at the start of one of the fields. Many things can cause it. In the early color section there was quite the thread on it by someone trying to track the problem down in a roundy color set.

Thanks Tom, could be! I did not change every resistor so will do some more checking.

Gregb

agreed a lot of things can cause it, but before assuming there is a problem, try adjusting the vert hold just a bit, often you correct the interlace that way.

if that does not help you can look into the vert integrator. One of my toughest dogs was a set that had bad line pairing that I could not clear up. I ended up scoping around and found a strong horz pulse getting into the vert due to a leaky yoke. I new yoke cleared it right up. these kinds of problems are best sorted out with the help of a scope IMHO.

Got my set working with a good picture now. I checked every single resistor in the set and had to replace all of the 5% ones as they were all out of tolerance and a fair number of the 10% ones. I went back and checked the few I did not change as they tested ok and some of them were way off one was 100% high. I guess once they got heated up and under load again after all these years they failed.
Looks great now!

Gregb

New problem has come up now that I have the TV on for more than a minute at a time. There is arcing in the neck of the picture tube. The tube tests good with no shorts or other problems but there is a random blue arc the seems to go away after its been on for a 5 minutes or so. Seems to sound bad more than anything else and it does make the picture jump until it settles down, Any thoughts on this?
Thanks

Gregb

New problem has come up now that I have the TV on for more than a minute at a time. There is arcing in the neck of the picture tube. The tube tests good with no shorts or other problems but there is a random blue arc the seems to go away after its been on for a 5 minutes or so. Seems to sound bad more than anything else and it does make the picture jump until it settles down, Any thoughts on this?
Thanks

Gregb

inside the tube?

Yup, Inside the tube. Nice big bright blue spark.

Gregb

Yup, Inside the tube. Nice big bright blue spark.

Gregb

Could be a gassy tube. I have a roundy tube that tests great, but the cut off test on my B&K tester which says to turn a knob to get 2 division change on meter will not work as described (it is either nothing or way more than a 2 division jump, I can't adjust it to rest anywhere near 2 divisions). They describe that as the symptom of a gassy tube. I've heard it aptly called 'neon tube action' basically no current is conducted until threshold voltage is reached, then it conducts as much current as you can give it.
My roundy CRT installed in a set will have purple neck glow, and as soon as the HV comes up there will be a big blue arc between the electron gun and the HV inside the tube.

Your CRT has probably leaked to the border line of what my tube has become.

I would agree but it stops doing it after a couple minutes and there is no blue or purple glow which would indicate gas. I also find that most gassy tubes test real good, almost too good and this one tests at about 400 on my B&K 460 crt tester. Not great but not terrible either and the picture looks just fine with more than enough brightness and real sharp focus.
Strangest thing I have seen.

Gregb

Well I stumbled onto the reason for the arcing in the tube. One of my newly installed capacitors failed. I don't know what its purpose is but it was a.002uf 1600v cap across one winding of the HOT and it failed. I was sitting there watching it and it did it usual couple of arc's and then seemed to be fine and about 15 minutes in it did another arc and this time the horizontal and high voltage went out. After a little checking I found my new cap had shorted. So I found another one and installed it and now no more arcing at all and an even better looking picture. The first cap I put in must have had a problem right from new.

Gregb