a real challange?

[Yamamaya42]

Contrast control mod for FADA (rca 630ts clone)...

https://imgur.com/0pAv0eh

this circuit was literally copied from the CTC-16/XL.
The same appears in many other RCA color sets with only slight variations.
The FADA has a 330 ohm resistor to gnd on the video output now, I see no reason why putting this in won't work as it does in the color sets, (just have to find s 330 ohm pot ), giving it a REAL contrast cont, and not what it has now, an adjustment for RF/IF gain that has an affect on both picture and sound.

[Kevin Kuehn]

So after changing all those bypass caps is your B+ back where it should be in the tuner and video IF circuits?

I can't remember if you showed us your tuner? I'm wondering if it's the standard coil type, and if so have you tried adjusting the local oscillator adjustment for the individual channel you're set to? If it has those adjustments they can be off enough that the fine tuning won't get you best picture and sound.

That contrast mod should work. Likely you can even use a 500 ohm pot. However you'll still need to set the rf/if gain for best operation as there is no AGC in this set. But you'll at least have separate gain control over video.

[Yamamaya42]

Originally Posted by Kevin Kuehn

So after changing all those bypass caps is your B+ back where it should be in the tuner and video IF circuits?

I can't remember if you showed us your tuner? I'm wondering if it's the standard coil type, and if so have you tried adjusting the local oscillator adjustment for the individual channel you're set to? If it has those adjustments they can be off enough that the fine tuning won't get you best picture and sound.

That contrast mod should work. Likely you can even use a 500 ohm pot. However you'll still need to set the rf/if gain for best operation as there is no AGC in this set. But you'll at least have separate gain control over video.

It seems to be the standard tuner as it appears in the sams, I have not tried to adjust anything else other than the 1st IF at this point.

The voltages are up a bit more to where they should be, it seems that the voltages shown on the riders (& rca 630ts service manual docs ) are misleading, after looking at it for some time, it hit me, how can the voltage on the plate of the 1st IF tube be @ 135v, if the source bias is 135v, going through 3 150 ohm resistors and 1 1k one? It can't be...
It must be wrong.
Sams shows it to be 95v
And sams shows the (135v) to be 117v.. :/

mine are now very close to that, so I guess the voltage was mostly OK to start with.
But still, when I tried to go “by the book” to adjust the 1st if, it did not work right.

1) remove osc tube, did that...
2) DC probe at junction of R40-R41, adjust “contrast” to -3 volts, leave it there.
This did not work, it cut off all input from tuner/if , no input defection at all, had to take it up to -1.2 to get it to do anything, and when I did try at that point, it ended up worse than when I started.

It was this point I replaced the WHITE waxy caps, and re-adjusted 1st IF visually, to get to where I am now.

[Kevin Kuehn]

Originally Posted by Yamamaya42

1) remove osc tube, did that...
2) DC probe at junction of R40-R41, adjust “contrast” to -3 volts, leave it there.
This did not work, it cut off all input from tuner/if , no input defection at all, had to take it up to -1.2 to get it to do anything, and when I did try at that point, it ended up worse than when I started.

Sure seems to indicate a lack of gain in the tuner, which coincides with snow in picture. I wonder what would happen if you inject your alignment signal to a tube shield hovering over the local oscillator tube, so it's not grounded. That should capacity couple the signal so it's fed to the first IF stage. If that doesn't work I'd try through a capacitor to the first IF grid. [edit] forgot to mention you need to snip I think pin 1 on a 6J6 to capacity couple through a shield over a 6j6, which I think is the plate. Basically disables the oscillator and couples to the 2nd rf tube.

[Yamamaya42]

Originally Posted by Kevin Kuehn

Sure seems to indicate a lack of gain in the tuner, which coincides with snow in picture. I wonder what would happen if you inject your alignment signal to a tube shield hovering over the local oscillator tube, so it's not grounded. That should capacity couple the signal so it's fed to the first IF stage. If that doesn't work I'd try through a capacitor to the first IF grid. [edit] forgot to mention you need to snip I think pin 1 on a 6J6 to capacity couple through a shield over a 6j6, which I think is the plate. Basically disables the oscillator and couples to the 2nd rf tube.

I'm rather worried about the 2 150 ohm resistors in the tuner's rf amp section, they are the same kind that were in the IF section, (all bad), and if they are as bad as this one, it's no wonder there is poor gain.

https://i.imgur.com/gBixele.jpg

there is a point E, that they suggest feeding in a signal into when alignment it REALLY bad, it's on the far end of the mixer coil stack in the tuner, and feeds into 1st IF.

I have found very few resistors bad above 1k ( just a few), but so far EVERY ONE, of the 150 ohms has been bad by 60%-190%, and there are 3 in the tuner
but I really dread pulling it out to replace them.

[Kevin Kuehn]

Originally Posted by Yamamaya42

I'm rather worried about the 2 150 ohm resistors in the tuner's rf amp section, they are the same kind that were in the IF section, (all bad), and if they are as bad as this one, it's no wonder there is poor gain.

See below.

there is a point E, that they suggest feeding in a signal into when alignment it REALLY bad, it's on the far end of the mixer coil stack in the tuner, and feeds into 1st IF.

This sounds reasonable to try.

I have found very few resistors bad above 1k ( just a few), but so far EVERY ONE, of the 150 ohms has been bad by 60%-190%, and there are 3 in the tuner
but I really dread pulling it out to replace them.

You can measure B+ plate resistors in the tuner between tube socket plate pins to some other B+ point accessible outside the tuner. If there's more than one in series simply add up their values. Then you will know instead of wondering. Study the schematic and you may be able to sniff out others using the same method.