My CTC-16XL Project.

[Yamamaya42]

Got the new parts today as expected, and it never ceases to amaze me how much resistors have advanced since the 60s, I mean they ARE 1w but they are ¼ the size of what they are replacing, and will most likely last much longer!

WOW, just wow!

[dtvmcdonald]

"¼ the size of what they are replacing, and will most likely last much longer!"

Also, a certain bridge to Brooklyn is 1/4 the size it used to be, but carries as much traffic.

If they are that much smaller, they will run that much hotter. Its the laws of physics.

Because they are hotter they may well not last any longer than the old ones.

But worse ... being hotter, they are more likely to damage other parts close to them.
You need to space the new ones out so that they are centered exactly where the old
one was. Even then the spot directly above them gets hotter.

In general, if an old resistor is rated more than 1/2 watt, I make sure the new one
is roughly the same size, even if much higher rated. If the old one was 1/2 watt,
I just check and make sure the new one is running at less than 1/3 its rating, and is long enough to take the peak voltage across it. Of course lots of old 1/2 watt carbon resistors were run at far less than 1/2 watt.

[Yamamaya42]

https://www.mouser.com/datasheet/2/4...03-1762580.pdf

It's unlikely that heat will be an issue with these at all, I chose “power resistors” vs standard ones, and the rated voltage @ 350 is far beyond the original carbon composites, and even if they do run a bit warmer, they are going to be mounted raised a bit & not flush like the old ones were.

[Yamamaya42]

Another thing to keep in mind, the newer ones are much better in dissipating heat than the old carbon composite resistors, and thus are substantially smaller.
I can't find by what factor exactly they have improved, but it seems by being made of better materials, IE glass/ ceramic cores vs doped carbon, and thinner insulation ETC, what physical size resistors that were approximately 1W now are 3w, so on and so forth, this is how they have progressed things.

[Yamamaya42]

i put in one new resistor , the one that was worst off, just to see what difference it would make.
https://i.imgur.com/joQpdzx.jpg


and you can see on the thermal scan how much cooler it runs vs the old carbon ones.

also it DID change the center.
https://i.imgur.com/S6HMTfL.jpg

[Yamamaya42]

Parts on the convergence PCB changed, the new resistors do run cooler than the old, things made an over all improvement but STILL having a hard time with RG vert top.
Having to adjust R27 to the extreme to get it close, leaving R217 out completely gets it even closer.

All this has made a 15% improvement, parts on the convergence PCB & 6GF7A.
Will mot likely add replacing that C4 with a exact 50uf cap when I ever have the chassis out next and see what does, but done working with it till next time, there is ALWAYS a next time! :O

[Yamamaya42]

https://www.youtube.com/watch?v=cURROx6hcv0

all room heaters on at once!

[old_tv_nut]

At this point, I think I would try sliding the convergence coils forward and backward a little to see if they are not exactly over the internal pole pieces. It should not be necessary to run R27 to one end. Are any other controls way off center?

[Yamamaya42]

R27 is the only one acting that way, and has been ever since the set was gotten working again.

Thus I have been suspecting the 56uf on place of the 50uf at C4 for some time now, I'm not even sure of the status of R106 which is under the PCB, this may be sending a wave slightly too big/small to that circuit on the convergence PCB making it ALMOST in range.


Obviously the 2 resistors from the cathode of the vert output to ground are OK R127/R126 ( also tied to pin 8 of HOT ) as there is no problems with sweep.

[Yamamaya42]

https://www.youtube.com/watch?v=XfnvND-Kb5Q

video test after latest convergence

RF input

[kvflyer]

Originally Posted by Yamamaya42

https://www.youtube.com/watch?v=XfnvND-Kb5Q

video test after latest convergence

RF input

Looks great!

[Yamamaya42]

Yes, still working rather well via tuner, given that I got it after a mad tweaker got done with it and lost the cover to the IF section, removed the color PCB and did unspeakable things to it like replacing the color takeoff and bandpass coils when it was not really needed. :/

It's working real well with LD video and unlocked DVDs, but as usual for sets of this era, trying to use a cable box via the tuner ends up in buzz-O-matic city, so rather than trying to readjust the audio section to any given channel I'm trying to watch via cable, I just hit the bypass switch and go direct A/V input.

but it's good to hook up the rf modulator once in a while to see that the tuner / IF is still happy and healthy!

[Yamamaya42]

On a completely unrelated note, ( to my 16XL) anyway, I now know with relative certainty what was wrong with the Roundie of my childhood , the RCA, CTC-10A "The Sullivan" from our grandparents that my dad gave up on trying to fix and just got rid of.
Although I was very young at the time, I was always watching him trying to work on it and remember exactly the symptoms it had, it would work fine when first turned on, good picture, good color, nice and stable, but as it warmed up it got unstable, jittery.

He spent weeks/ months playing with it before he gave up, replacing tubes, resistors, capacitor NOT electrolytic filers though.

But the one thing this IBM engineer overlooked, and was most likely the fault, the selenium horizontal phase detector.

What a waste...
I wish I had a pu truck and a flux capacitor right about now.