Motorola roundie
 

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.

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.

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

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.

retracted

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.

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.

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.

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.

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.

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.

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

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.

It has been many decades, and failing memory, but here goes.
In the shop we used to generically use this method. Set must be warm.
Ground the grid of the 3.58 reactance tube. If you get multi-color stripes (a must either way) on a TV picture or low input color bars, adjust reactance coil for single color per vertical bar or the color picture syncs.
If that doesn't work try the same with the 3.58 tube and its output xfmr to the demods.
It's been a long time.
Good luck.

What’s the easiest way to tell if the 3.58 crystal is bad ? Or going bad. Turn on got color bars let it warm up shut it off turn back on color is fine.

Depending on the chassis, a bad crystal may give no color or a greenish picture. If you have color bars, the crystal is fine.

This one is easy. Locate the burst amp on the tube chart. Remove it. Adjust the oscillator coil (the one closest to the chroma oscillator without the shield) to zero beat the color. Reinstall the burst amp tube. Regardless of shifty drifties this will keep you out of trouble for a while.

again if you go through the color AFC alignment procedure listed in the SAMs, it may solve the problem, but if it does not, you have parts in the color circuitry that have drifted too far out of tolerance, and temperature is having a direct impact on this.

So I’m going to get the set on it’s side and take the metal cover off the bottom to gain access to under the chassis so I have 1st&2nd chroma bandpass burst amp and chroma sync phase det which one maybe responsible for color bars not syncing as I’m going to look for bad resistors since getting done with this set the color was fine so it’s probably a resistor that drifted alittle to far out.

Since you are dealing with a temperature related issue on an older set, it may be advantageous to go with higher testing parameters when checking the resistors, especially when newer higher tol ones are much cheaper and very available, example, if the part is a 20%, reject and replace if it's out at 15% with a new 2% part, and if it's a 10%, reject and replace if it's like 7% or worse, or thereabouts.
Reason being, the more the old parts age, the more they will slowly drift out of tolerance and tend to be affected by temperature, the more newer parts placed, the less you will have to deal with later.

This may help or hurt. Been 50 yrs & if wrong please correct.

Burst amp pulls the color sync off the horz blanking pedistal. It on the " back porch " and 8 cycles. Hoz osc pulses gives it the narrow grab, the
burst tube amps it & passes it to the 3.58 for sync.
No burst gives barber pole color or no color. The burst adj can "center" the
tint range.
Dead 3.58 gives a classic pink & green on many sets (RCA), no color,
wrong colors, barber pole. Xtals do go bad but not often. If the
XTAL has a third GND wire use that type.

enuf
Zeno

Well it’s got to the point that warming it up is not working so its more then likely it’s a resistor or maybe even a tube I will have to check them I also thought that maybe it’s the alignment but i got a really good b&w picture and when the color locks the picture is perfect or maybe a weak signal coming from the trap to the video detector. Don’t really know yet.

Been about 55 yrs for me, but I remember it vividly: House call, Zenith console, no color. Subbed tubes, tried color killer, nada. Shopped the set and it was the burst tube, a 6EW6. I had missed it. No excuse, just dumb. Boss wasn't amused. Funny how one remembers one's *bleep*-ups with such clarity.

Was is the pole color referring to color bars up and down or left to right. I have left to right.

Kinda hard to describe but usually color bars rolling up. Can be many
bars or just a few rolling by slow. L-R says purity but if B&W is good
thats not it.
Find & check the hoz out sample lines. They go to burst, hoz blanking,
AGC & conv. Can cause some odd problems.

Zeno:smoke:

What it should look like w/o color sync lock

https://imgur.com/m0IePGv
https://imgur.com/Tvyc044

From when i was fixing color on my CTC-16XL

https://imgur.com/9HcgQcz
with the ref crystal disconnected.

Yup that’s what I’m getting

So far I’m not finding any out of tolerance resistors I double checked tubes also so this loss of color lock definitely seems like a bad resistor what part of this circuit takes the biggest beating. I didn’t get into the afc as the color was fine it just started to lose sync and gradually got worse like a resistor so I don’t believe the afc would have anything to do with this it was not touched. I have a new crystal but it’s being said that having color bars the xtal is good so I didn’t try it.

Can a 3.58 xtal be paralleled temporarily with the old to see if the old one is bad ?

https://img.freepik.com/premium-vect...544.jpg?w=2000


The chances of this being related to the crystal are pretty much none whatsoever.

It works or or does not, you can not put 2 in place that won't work.

You are looking for something that changes state from cold vs warm/ hot.

Then obviously that would be a possible tube or probably a resistor for sure I just wish I can find it because all the resistors are checking perfect or less then the rating. It’s frustrating

less? that may also be a sign.

I would use this...

https://www.allaboutcircuits.com/too...de-calculator/

and test on the 5% scale and be suspect of anything that does not fall within that 5% range.

Are you checkig the resistors while they are still connected in the circuit? This will generally result in a lower reading because of parallel current paths.

Some I checked in circuit but the ones that showed less I mean 100k showing 97k so it’s not much.

I fought an issue with high HOT current, I had checked all of the resistors and they measured good. Finally I started shotgun replacing resistors in the horizonal circuit, each pulled resistor measured good until ultimately had a resistor break apart as soon as I clipped the first lead. The resistor either failed after I measured it or the fact that it easily broke maybe it only was failing under load and somehow measured good.

You could go back and re-measure resistors paying extra attention to visually suspect resistors. Also as others noted pay attention to parallel resistors; with the way some of the B+ is feed to multiple circuits there could be a lot of resistors in parallel. Worst case you can pull a lead to measure, of course then you are 50% towards just replacing the resistor.

Indeed some faults are frustrating to find.

Just now, I'm fighting (I will, when I have proper time) with a issue with vertical of my Telefunken delta-gun TV. Very irritating, since this occurs only sometimes, and is heat related: this not occurs when TV is cold, and most times not occurs when is hot. Most time only occurs with thermal transition (when warming) :sigh: so I donb't have much time window to play with
Then, I need some clear time to try to find the culprit, but certainly has a culprit. I need to study well the schematic, for not shotgunning every related part, but the bhegges idea sounds very good now...

Is curious that this defect ocurred 6 months ago, vanished, and returned now, go figure...

Back in the day TV techs used to find thermally dependent faults with freeze spray. Get some canned air or that old radio shack tuner cleaner that is basically oil that comes out of the can frozen and with the set on and the chassis jigged so you can access everything in the circuit with it running hit every component in the offending circuit a few at a time once warm and see which component when chilled puts it back to the cold operation state, once you find a region of the circuit that effects it narrow your chilling until you isolate the exact part that's causing it.

We used to keep a movers blanket to throw over a set to hasten warm-up (not unattended of course), then go in with the targeted Freez Spray. You could probably use a hair dryer for a quick warm-up too. Don't any of the supply houses still carry the spray?