a real challange?

[JohnCT]

Originally Posted by Yamamaya42

So, from what I understand, the cheapo mega328 tester should be able to test the coils in my tv, 93uh – 250uh, cause as mentioned, I only found 1 of the 2 new 93s needed, so I will have to re-use whichever one that's in there that tests best, and from what I read, the new ones need to be put in exactly the same way as the old ones... just how critical is that?
If coil #xx1 was ##mm on the left side with the leads, and ##mm on the right, sitting ##mm above the metal chassis, does the replacement have to be exact, or is there some wiggle room?

I was screwing around with my 328, and it's pretty accurate with capacitors, ESR, and even inductors over 10uh are close enough. What it's not accurate at is resistance under one ohm. A 0.47 read 0.33. On my Fluke, it read 0.46.

Any component in the IF should be replaced as close to its original physical location as is possible. Even moving a part aside to resolder a tube socket has some (possibly insignificant) effect on alignment. In any case, you don't want to leave long leads.

John

[Yamamaya42]

Originally Posted by JohnCT

I was screwing around with my 328, and it's pretty accurate with capacitors, ESR, and even inductors over 10uh are close enough. What it's not accurate at is resistance under one ohm. A 0.47 read 0.33. On my Fluke, it read 0.46.

Any component in the IF should be replaced as close to its original physical location as is possible. Even moving a part aside to resolder a tube socket has some (possibly insignificant) effect on alignment. In any case, you don't want to leave long leads.

John

the coils in question ARE in the video amp section, so that's why I'm wondering.
https://imgur.com/vXqVDJB
I ca see how in the IF area it really does, but does it in the video amp as well?

[dtvmcdonald]

An IF (or RF) is a high-Q circuit, the coils in video amps are in
low-Q situations. They are less critical, but try to get them right, especially
distance from the chassis.

[Yamamaya42]

That's odd, there are 2 types of 1500 PF caps in there, even though it's not mentioned on the docs.

the white ones sealed with wax that look like paper ones, and brown ones ( open ended, both are tube shaped )

there are these https://imgur.com/FDVtxmP

and these
https://imgur.com/ObBmxmO

[Yamamaya42]

am I reading those little brown tube caps right? brown green red green, 1500 pf 5%?

EDIT

I guess i will have to change my approach

i have these, https://imgur.com/vY5TIS7
Which I'm still not sure what type they are, but they match the part list, 1500pf 350v 20%, the wax ends are very suspect, they may be leaking wax. Been replacing with film type 650v 10%

then saw this in there.
https://imgur.com/Gdv9iop
5% from what I can tell, so it would be unwise to put 10% in there...
gonna look for some highly stable 3% kinds.

[bandersen]

Those are ceramic caps and rarely go bad. Don't worry about the tolerance. They are simply bypass caps.

[Yamamaya42]

all the waxy white 1500 caps replaced.

tried again
https://www.youtube.com/watch?v=Id3OWPlHtVo
behaving a bit better now

still snow in pic, I got it this way bu visual adjust of 1st IF coil this time rather than trying to follow setup instructions.
not sure if the other coils are right or not, or if there may be problems in the tuner as well , out of spec resistors , there are a few of the same 150 ohm ones that were VERY bad in the IF strip, some almost 2x too high, but getting that thing out of there to get to them is a pain it the ass, and I dread attempting to try.
I wont have all the new peaking coils for about a week, as 3 of them are coming from Canada.

If i do try the IF alignment as per the procedure again, I will most likely try with a digital RF generator with amplitude control, but that may take a while to get one :/

[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.

[Yamamaya42]

https://imgur.com/y84aCsd
OK..
I can't get a stable reading of any resistance between pin 1-2 , it's jumping all over the place, prob from going through all the coils, nor can i get a stable reading of resistance to the point "red wire" but there is 68v on both plates, ( sams says 50v)

between pins 5-6 was 438 ohms, ( additive of the 2 150 ohm resistors ), voltage at those pins changed dramatically with picture (contrast ) control.

[Kevin Kuehn]

Originally Posted by Yamamaya42

https://imgur.com/y84aCsd
OK..
I can't get a stable reading of any resistance between pin 1-2 , it's jumping all over the place, prob from going through all the coils, nor can i get a stable reading of resistance to the point "red wire" but there is 68v on both plates, ( sams says 50v)

between pins 5-6 was 438 ohms, ( additive of the 2 150 ohm resistors ), voltage at those pins changed dramatically with picture (contrast ) control.

From either pin 1 or 2 of the rf amp to the red B+wire you should read around 3,500 ohms if R1, 2, 4, 11 were close to as marked. R1, R2 are paralleled by the tuner switch and those are in series with R4, R11. It's possible your meter is charging some cap, but I'm not seeing it at first glance. Or maybe the meters voltage is setting up an oscillation, who knows. All those tuning coils should read relatively low DC resistance compared to the higher total resistance. Anyhow it appears you now have a decent B+ getting to those plates, so I'm getting a little lost with the ups and downs.