This I believe is a definite NO - Mostly because the voltage of the signal is
too small as Yamama said, but mostly because the sync pulse is not
"syncing" anything.... In your screen shot it looks a lot like a Whometco
home theater image after they turned on the late night pay service.
In this pay service they use to suppress the sync pulse and the
picture locked on any semi-dark part of any image.....
What you got was a pretty scrambled image if
you were not a paid subscriber....

You had a better lock with the tuner subber on V2. That might have
done a little for your AGC, and well worth checking.... If you had
nothing else to do......

DAMM another freaking page!!!!!


.

This thread needs s sticky, or its own forum. Its pushed a few other interestingnposts down a bit…

. Hv adjust works ok 10pm resistor is 11 ohms

Unless someone knows this Motorola chassis and how certain things work being they are different then most other chassis there is a reason why L42 is overheating and until I can find out why then this project will probably hang in the balance with lots of guessing and assuming I can only hope I nail it soon.

I think once I get the snow on the screen then I can say I got it. The 470pf cap I think has something to this whole puzzle because something has to conduct with this cap it cannot just be there to look good so the question is what happens at this junction with the cap and the tube I do believe both are related in some way here. Ac or dc on whatever end of the cap something supposed to happen here that I don’t think is happening.

First and foremost, the loss of L42 is not going to mean a catastrophic end of this set, YES, there is no replacements to be found on the market, but this is nothing new to people who restore vintage electronics, and as I recall there is at least one person (if not more) out there who has the equipment to wind their own replacement coils, who I no doubt would be more than happy to help you out in replacing this coil.

Also, as been stated several times, you have yourself severely hamstrung, there is only so much you can do with the limited tools you have on hand, digital multimeters, soldering irons, a schematic, a handful of parts can get you only so far, complex issues like you are having need an oscilloscope and the general know how to use it, otherwise you will keep hitting walls, over and over and over.

You have been given tips by Squirrel boy and myself to try and protect L42, it's your choice to use them or not, it would be in your best interest to do so and turn your attention to the tuning / IF problem first.
Even if putting in this protection degrades the ability to focus a bit.

Things I have been wondering.
What prompted the replacement of the FBT in the first place when the original seemed OK?
This is an extreme measure, and only done when you are VERY sure it's bad.

What caps were replaced in the set?
In this era there are only 2 known that will be problematic.
Electrolytic capacitors and any obvious paper capacitors.
ALL ELSE should be left alone unless you can show that they have failed.
These include all ceramic disc capacitors and sealed film types (drop caps).
To arbitrarily replace the above w/o reason (proof of fault or fail) is asking for a major headache.

The way choose to go on from here is yours, but your best choice is to protect l42 as mentioned.

I do plan on putting in the resistor for L42 and the reason I originally changed the flyback was the low hv and the caps I changed were in and around the horizontal oscillator and the sync circuits the rest I left in the set then with the new flyback it kept red plating the hot that don’t happen anymore since putting the old one back in. The power supply caps I checked for mistakes like a 190v on a 275v tap but all is good by checking tube sockets where power goes to make sure the right voltage is there.

You can think of the AGC as sort of a comparator circuit.
The reference is the pulses from the FBT via C59 there is boost potential on the far side of C59, thus it is a 2kv part, the pulses are 450v ptp.

It gets compared to matching pulses from the video amp that is being fed in via the tuner/IF, if this is too low, it will raise the gain of the IF and tuner stages, if too high, it will lower it.
The matching pulses from the video amp can be enhanced / adjusted with pulses from the FBT via C60 & R14, but if there is no incoming video, or if the video at the video output stage is too low, then AGC will be stuck thinking that levels are too low, and lock the gain at the highest level, and R14 will have no effect no matter how you set it.

Again, there is 700+ dc boost potential on the far sides of C59/C60, but should only be passing AC pulses to V6, if they are passing DC, then they are leaking and bad.

Those 2 caps you mention are the 470pf and 2.2pf I guess it wouldn’t be a bad idea to change them both I do have them or I should lift one leg on each cap and check for ac or dc. At this point I don’t know the next step to take with the video.

whats the voltage rating on this new 2.2pf cap you have? is it a NPO?

The 2.2pf is 1kv and it is supposed to be a npo it’s old new stock.

This one, most likely.
https://talonelectronics.com/shop/item.aspx?itemid=9535

you could replace them, but it would most likely not change anything function wise. :(

It is supposed to be npo but does not show it on the cap all it shows is n750 2.2 +25 1 kv

if it has a black mark on the top then its NPO.

No black mark just RMO