Motorola roundie

[timmy]

I’m looking for a cause that would be responsible for color bars on screen when turned on it looks like loss of color sync when I let it warm up for a few minutes I turn it off then back on and the color is fine. Maybe possible dirty tube pins or sockets all tubes are good but then again I have had bad tubes that test good.

[Yamamaya42]

That's nothing unusual for these older sets to do as the warm up, normally when they do it, I'd briefly turn horizontal hold pot in and out of sync a few times, and it will always get it to lock as it warms up, but since the ts-907 has none, not sure what to suggest.

[timmy]

Well it has horizontal in the rear but that’s not realistic to have to go in the back to do that.

[Yamamaya42]

That's why I mentioned not sure what to do about it with yours, as there is no easy access horizontal hold pot, in most cases for color lock, the burst amp is using a pulse taken from a winding from a isolated part on the very lower part of the FBT, and when first turned on and there is no color lock when cold, very often adjusting horizontal hold till it loses sync and back gives the color circuits the kick in the pants it needs to lock in, and it tends to stay locked for then after.

I learned that trick from watching shango066's videos :O

[timmy]

Originally Posted by Yamamaya42

That's why I mentioned not sure what to do about it with yours, as there is no easy access horizontal hold pot, in most cases for color lock, the burst amp is using a pulse taken from a winding from a isolated part on the very lower part of the FBT, and when first turned on and there is no color lock when cold, very often adjusting horizontal hold till it loses sync and back gives the color circuits the kick in the pants it needs to lock in, and it tends to stay locked for then after.

I learned that trick from watching shango066's videos :O

Ok well then I’ll give that a try to know if it works then I’ll turn it on the next morning then that will tell.

[reeferman]

retracted

[timmy]

So I took the horizontal out of sync and then back and has color bars then it popped in then I changed the channel to see if the color goes out of sync and it did but I moved the channel selector and again it came back in so it’s a bit inconsistent.

[Yamamaya42]

This has to do with parts being on the verge of out of tolerance CAPS RES, so on, 20%, 10% and the change as the set warms, since most adjustments are done warm, it's not unusual to see this weirdness on older sets when cold, the only real way to avoid it is to go overboard when you restore, if it says 20% test and replace at 10% or higher, if it says 10%, shoot for 5%, I myself have been using 2%, and only very rarely see the cold no sync problem.

[timmy]

Well all the caps were changed as well as resistors but I don’t recall being in the area responsible for color sync because upon finding why I had no video after fixing that I had perfect picture and color it seems after sitting for a week or so this happens more and I run it today and then turn it on tomorrow it’s fine so who knows.

[Yamamaya42]

You may want to consider running through the color AFC alignment procedure another time, keeping in mind that any parts that are close to tolerance in / out , resistors and critical caps, (NPO, and the like) will leave the set susceptible to drift as it warms up, heck, even changing tubes sometimes can do it like I saw on my latest Magnavox tv.

[timmy]

I may look into the tubes in that circuit because there was talk about tubes from the 60s that will test good but in reality are not good for whatever reason other then they are old.

[Yamamaya42]

It's less likely an issue of good/bad tubes, and more likely an issue how a tuned circuit is reacting cold vs warm ( phase locked loop)- burst amp and color oscillator control, options are to try to adjust it to minimize the drift hot and cold so you don't lose lock OR replace with optimal parts so the drift is eliminated.

[old_coot88]

Did roundie-era Motorolas use the 6LE8 all-in-one high level demod setup, or did that come in later? Moto wasn't a house brand, so we didn't get a lot of them in.

[Yamamaya42]

Originally Posted by old_coot88

Did roundie-era Motorolas use the 6LE8 all-in-one high level demod setup, or did that come in later? Moto wasn't a house brand, so we didn't get a lot of them in.

the one he as uses a 6bl8

[timmy]

I also have a very faint white line on the screen at the 12 and 6 position only on dark scenes can it be seen it don’t affect the picture quality but I was a bit curious as to what would create this line.