Motorola roundie

[nasadowsk]

We don’t have any waveforms to look at?

[timmy]

Is it at all possible to have the lock that I have now with missing colors for the oscillator to be off frequency. A18 measures 5.7 ohms should be 2.6 ohms question is could this make the difference between the right colors or wrong colors.

[Yamamaya42]

Originally Posted by timmy

Is it at all possible to have the lock that I have now with missing colors for the oscillator to be off frequency. A18 measures 5.7 ohms should be 2.6 ohms question is could this make the difference between the right colors or wrong colors.

https://www.youtube.com/watch?v=0-4Jb0rC8Io

YES!!!

[timmy]

Originally Posted by Yamamaya42

https://www.youtube.com/watch?v=0-4Jb0rC8Io

YES!!!

I was referring to the frequency created by A18. There is still the 15pf mica in a A18 which could be out of tolerance only way to rule out is to change it

[Yamamaya42]

If the SAMs is correct, and A18 should be 2.6 and you got 5.7 ohms that, that is a big problem if that is really what you got, and very likely why the old crystal won't work, again THAT is the problem if the reading is correct.

there is a flaw in the winding of the coil, or a bad solder connection

[timmy]

Originally Posted by Yamamaya42

If the SAMs is correct, and A18 should be 2.6 and you got 5.7 ohms that, that is a big problem if that is really what you got, and very likely why the old crystal won't work, again THAT is the problem if the reading is correct.

there is a flaw in the winding of the coil, or a bad solder connection

Well I will have to disconnect the wires going to the coil and if the ohms are still not right I will have to pull the coil and clip one leg of the 15pf because it’s parallel with the coil. If the cap is a problem it should show quickly.

[old_tv_nut]

Originally Posted by timmy

Well I will have to disconnect the wires going to the coil and if the ohms are still not right I will have to pull the coil and clip one leg of the 15pf because it’s parallel with the coil. If the cap is a problem it should show quickly.

Leave the 15 pF alone! It cannot cause the resistance reading of the coil to read high, only lower because it is in parallel.

[Yamamaya42]

Originally Posted by old_tv_nut

Leave the 15 pF alone! It cannot cause the resistance reading of the coil to read high, only lower because it is in parallel.

exactly, the capacitor is irrelevant at this point, and would not cause the high resistance reading hooked in parallel.

you need to VERY closely inspect the coil wires, and were and how they are soldered, and what could be causing it to be high.

And once you hopefully find the fault and fix it, try it once again with the original crystal, not the new one.

[timmy]

Ok coil out checked it 5.8 ohms and for giggles I clipped one end of the 15pf cap still 5.8 ohms so I could try reflowing the solder joints on the coil and see otherwise the coil is not burned or discolored actually looks good

[Yamamaya42]

according to the SAMS that i 2x too high, and can't work.

[timmy]

Originally Posted by Yamamaya42

according to the SAMS that i 2x too high, and can't work.

Maybe I can rewind it with wire same size to 2.6 ohms. I could use a caliper to measure the wire diameter I have a focus coil which looks like the wire maybe a match I have another coil but the wire is to thin.

[Username1]

Good Afternoon,

I think rewinding that coil is not a good idea.... I think at this point you should think
about 2 possibilities. 1. The incoming burst signal is distorted because of a bad part,
or there is the other possibility, 2. A19 is not tuned to the burst signal..... I thought
about this a lot, and found stuff written about this group of circuits to refresh my
memory on every inch of these circuits. None of the circuit descriptions go into
"restoration" and replacing parts because they are believed to be out of
tolerance. So when you consider the large number of parts replaced in
this tv, I bet there are lots of circuits somewhat out of tune.

As of right now I have not seen a post where anyone has said A19 has been adjusted
for anything..... I wonder if that coil should be adjusted to see if it's out of tune and
causing the burst signal to be off by a little bit.

Back to A18, Timmy can you take that out and send us a good close up picture of it?
While I'm a fan of replacing parts that are out of spec, this one is only out of spec
as far as it's DC resistance goes..... You really need an Inductance Tester Gadget
of some kind to tell if it's Mili-Henry's or Micro-Henry's are out of whack, or not.
And wouldn't ya know it, Sam's don't give it's value.....

I would say, that if you really want to rewind that coil, make a new one, but
keep that one as is - for when the replacement don't work....

Timmy, I think over the course of this thread you said you have a color bar generator?
If that is true, it may be time to get it out, set it up, run it through the tuner, and
try adjusting the tv Color & Tint to show them as they should look, I think third
from the right is suppose to be magenta - Kinda like Purple.... I think you
should try and set this up and see if you can figure out if there is actually
a color - or several colors that are not being reproduced properly. And
with a color bar on the screen try and adjust A19, and see what
happens..... I would think turning it would kinda make the
color saturation go up & down as it's passing the burst...
So you would be peaking the coil for burst signal....

Possibility 3. This is all wrong..... Problem is in
some other part.....

..

[timmy]

Originally Posted by Username1

Good Afternoon,

I think rewinding that coil is not a good idea.... I think at this point you should think
about 2 possibilities. 1. The incoming burst signal is distorted because of a bad part,
or there is the other possibility, 2. A19 is not tuned to the burst signal..... I thought
about this a lot, and found stuff written about this group of circuits to refresh my
memory on every inch of these circuits. None of the circuit descriptions go into
"restoration" and replacing parts because they are believed to be out of
tolerance. So when you consider the large number of parts replaced in
this tv, I bet there are lots of circuits somewhat out of tune.

As of right now I have not seen a post where anyone has said A19 has been adjusted
for anything..... I wonder if that coil should be adjusted to see if it's out of tune and
causing the burst signal to be off by a little bit.

Back to A18, Timmy can you take that out and send us a good close up picture of it?
While I'm a fan of replacing parts that are out of spec, this one is only out of spec
as far as it's DC resistance goes..... You really need an Inductance Tester Gadget
of some kind to tell if it's Mili-Henry's or Micro-Henry's are out of whack, or not.
And wouldn't ya know it, Sam's don't give it's value.....

I would say, that if you really want to rewind that coil, make a new one, but
keep that one as is - for when the replacement don't work....

Timmy, I think over the course of this thread you said you have a color bar generator?
If that is true, it may be time to get it out, set it up, run it through the tuner, and
try adjusting the tv Color & Tint to show them as they should look, I think third
from the right is suppose to be magenta - Kinda like Purple.... I think you
should try and set this up and see if you can figure out if there is actually
a color - or several colors that are not being reproduced properly. And
with a color bar on the screen try and adjust A19, and see what
happens..... I would think turning it would kinda make the
color saturation go up & down as it's passing the burst...
So you would be peaking the coil for burst signal....

Possibility 3. This is all wrong..... Problem is in
some other part.....

..

And yes I have a bar dot gen and I tried adjusting A19 and yes it increases saturation however it did no good. Bar gen I cannot get any other colors on the screen other then the pic on the post. The tint adjust is very minimal at this point and the intensity it’s range is not right. So if the oscillator coil is supposed to be 2.6 ohms and this one measures almost 6 so in an oscillator circuit I would think this should be right. I really don’t want to rewind another coil it probably won’t be right but I maybe able to get a NOS miller and would hope it works if it’s the problem.

[old_tv_nut]

The resistance of the coil is not the most critical thing, it is the inductance. There are several possible reasons your coil reads higher resistance, none of them indicating a failure. Two I can think of:

1)SAMS has a mistake
2) The coil construction was changed sometime during the production run to use thinner wire or more wire with a smaller slug

Since the oscillator can be tuned to the correct frequency, both the coil A18 and the 15 pF cap must be OK. Stop fiddling with this section.

EDIT: repeat the AFC alignment if you have turned A18 since you did it.

[old_tv_nut]

Stop fiddling with A19. Go back to the AFC alignment procedure where you adjust A19 for greatest voltage (meter "deflection"). Do not ever change this again.

Please post some pix with the color bars showing the result with the tint control max CCW, centered, and max CW.