Motorola roundie

[Yamamaya42]

Mosquito races?

never heard it called that before!

https://media.tenor.com/_gjYF8Z41hcA...oltergeist.gif

[timmy]

Well this time I decided not to tweak any slugs because the color sync was fine just gradually got worse then lost it completely so at this point it’s got to be a cap or resistor so I’m still on the hunt. There is a 220pf mica at the 6gh8 oscillator maybe it has the mica disease if I can measure that cap maybe something is up with that.

[Yamamaya42]

The chances of there being SMD in the set is very very low.

[timmy]

Well it’s always a possibility since I’m still not finding any bad resistors and I already changed the caps.

[timmy]

Something in this circuit is not oscillating I would suspect a mica before a ceramic cap.

[Yamamaya42]

Again,it's highly recommended that you have all NOS tubes in the color section, and NEW resistors would not hurt, but are needed if what you say is true, but it would still be better to replace the ones i mentioned with a matched pair at 2% tol, and THEN do the color AFC alignment E X A C T L Y as listed in the SAMS step by step, this very well may go a long way to solving the problems you are having.

[timmy]

Those 2 470 resistors each have a 330pf mica on them what’s to say there are good or not.

[timmy]

I just checked the 2 330pf micas one is 340 and the other is 350 pf I don’t know if this is considered to be to far out.

[Yamamaya42]

Originally Posted by timmy

I just checked the 2 330pf micas one is 340 and the other is 350 pf I don’t know if this is considered to be to far out.

These form a phase locked loop circuit, which control the color oscillator, the more matched you can get the parts, the more stable it will be, thus the point of having the resistors being a matched pair and very close tol on both caps and resistors.

[timmy]

Originally Posted by Yamamaya42

These form a phase locked loop circuit, which control the color oscillator, the more matched you can get the parts, the more stable it will be, thus the point of having the resistors being a matched pair and very close tol on both caps and resistors.

Does these micas sound like they are out to far to be any good being micas are for a stable exact circuit.

[Yamamaya42]

Originally Posted by timmy

Does these micas sound like they are out to far to be any good being micas are for a stable exact circuit.

unknown, it very well could be, but without being able to see the signal out of the detector, as shown on pins 1 and 2 on the SAMS at v22, there is no way to know, if things a wrong, the beat pattern will be messed up, uneven, missing, and so on, this will throw the color osc out of sync.

[old_tv_nut]

Originally Posted by timmy

I just checked the 2 330pf micas one is 340 and the other is 350 pf I don’t know if this is considered to be to far out.

Per SAMS, these are 5% parts. This tolerance is specified mainly for the match rather than the absolute value. So 340 and 350 is more than close enough to work as intended.

[Yamamaya42]

If it was MY set, I would replace the caps with these,
https://www.mouser.com/ProductDetail...Ntfni7EA%3D%3D

the 2 resistors with
https://www.mouser.com/ProductDetail...8mCiDAyg%3D%3D

and the 82pf c119 with
https://www.mouser.com/ProductDetail...95w9uDP1pRg%3D

[old_tv_nut]

These caps are encapsulated and only have 12 volts on them according to the SAMS and are therefore very unlikely to suffer from silver mica disease.

If you have not done the AFC alignment procedure yet, it is really important to do that before trying to trouble-shoot further. The first part of the procedure makes sure the phase detector is getting maximum amplitude signals, and the second part then makes sure the oscillator is at nominal frequency when the detector output is zero. If this second condition is not met, the oscillator will try to run off frequency and the detector will try to develop enough control voltage to center it again - but if it eventually drifts too far off, control will be lost. In this case, the color killer circuit may decide there is no burst and shut off the color unless it is cranked to one end to force color on.

[timmy]

I don’t know what to believe at this point what to change or what not to change.