My CTC-16XL Project. - Page 25 - Videokarma.org TV - Video

Yamamaya42 · #**361** 09-03-2019, 11:04 AM

In regard to protecting the FBT, given that there is near zero chance of finding one for a CTC-16X series, going from the starting point that it seemed in excellent condition to start with, ( no wax loss seen, or arcing traces ), it seems I was lucky getting this.
From all the many threads I have read, the most important seems to be HOT (6JE6A) cathode current, & keeping it as low as one can w/o losing function ( below 200ma).
To aid in this, converting the focus to solid state helps, as it removes the draw from it's heater winding.

What also is said to help is more ventilation for the HV cage, to allow any generated heat from the FBT/ HV RECT to escape more easily , this is done by adding holes in key places and forced air via fans, perhaps on the back.

At this point, I can't think of anything more to do to try and protect the FBT, as shown in the thermal scan before, w/o the back on that has the fans on it, the HV on mine is very cold after an hour running.

https://imgur.com/3hZnlmW

What can't be seen there, and this kind of surprised me, is I drilled 4 large holes in the front of the HV cage, and there is no heat at all seen coming from them, I did not expect things in there to be so cool as not to be able to see the holes on infa red.

Yamamaya42 · #**362** 09-20-2019, 10:40 AM

How does one know if a FBT has ever been replaced in any given RCA? There really is no way to know, is there, w/o knowing the history of the set. You can make a guess by looking, but never know for sure.
I have 2 examples here, Rocket's CTC-16XL and Freakaftr8's CTC-16.
I will look at mine closer this weekend.
I suspect that Freakaftr8's is original and Rocket's a replacement.
Reasons...
Freakaftr8's , Darkened metal at base, same as chassis, doughnut color darkened, wires held with black tape ( common with oem )

Rocket's , metal at base much lighter than chassis, doughnut color cleaner looking, no black tape seen.

https://imgur.com/d4cpPzR
https://imgur.com/W4JoHPn

freakaftr8 · #**363** 09-20-2019, 11:11 AM

I would say Rockets is for sure a replacement. That tape is usually a giveaway. Also the red silicone as well.

Yamamaya42 · #**364** 09-20-2019, 10:03 PM

https://imgur.com/LHDJKjQ
https://imgur.com/euosC1y
https://imgur.com/OMDJAt8
https://imgur.com/3a27NoW

Mine is def an original OEM.

however there is very little wax loss for a flyback that is this old, so I guess that is a good sign.

you can see the holes I drilled in the cover in one of the pics.

Yamamaya42 · #**365** 09-21-2019, 12:59 AM

Freakaftr8 you cursed my CTC-16XL!

tonight for some odd reason, the IF decided to fail again after working mostly for many months , now i get no video or sound T_T

i decided I was not going to bother hauling back up to the 2nd floor again and take it all apart to find out why at this point, but just switch back to video injection mode, and hope to fix it when ever I attempt to do an IF alignment on it. It gets better color this way anyway , the trade-off is retrace lines sometimes.
https://imgur.com/8wFk2gc <-- ignore the cheap cellphone cam shutter noise
pretty damn good for having bypassed the tuner / IF

freakaftr8 · #**366** 09-21-2019, 01:21 AM

Oh boy. This is the fun part of running vintage gear. its always something. reminds me of a certain Fold Thunderbird SC that I used to own.

Yamamaya42 · #**367** 09-22-2019, 09:41 PM

my TV via video injection
https://youtu.be/7V3etX2NsS4

freakaftr8 · #**368** 09-22-2019, 10:31 PM

Looking good! Did you figure out what happened to the IF stage? Mines dead too thanks to a bad 6KA8.

Yamamaya42 · #**369** 09-22-2019, 11:02 PM

My guess is that I lost another resistor in it someplace,

I had just a raster at first when I took it out of storage before I replaced R48 & R50.
then it was a huge fight just to get it to pass any color, It was still out of alignment bit mostly working.
but 90% of the original resistors are still in the IF section. I guess I should have changed them when i had the chance.
most of them were just in tol, and I posed the question should I just go and replace them now ( the old carbon core with new metal film ) and It was said, " if it aint broken "
Well now it is. T_T
but I don't want to go through the trouble of hauling it back upstairs and taking it all apart right now ( that damned metal cover on the bottom )
I'll prob wait till I get my hands on a good sweep function generator and try to do it all at once.

Electronic M · #**370** 09-23-2019, 12:08 AM

Quote:

Originally Posted by Yamamaya42

my TV via video injection
https://youtu.be/7V3etX2NsS4

Aside from the brightness looking a bit high and the retrace lines it looks perfectly fine.

When you have a few of these beasts in regular service you learn to bring the tools/workbench to the set and not the other way around... I have a particleboard shelf from a component stereo cabinet I use as a base to solder on so I don't burn the carpet. Having a dud brightener and some octal sockets and bases to make 3' extender cables so you can set the chassis ontop of the cabinet and use the set as its own workbench/test jig makes life easier too...Though the Zenith service saver bottom hatch makes life even easier...Just set the set on its side pull the bottom cover and back and every component is accessible and the set can be powered up for tests any time you want.

Yamamaya42 · #**371** 09-23-2019, 08:22 AM

It's not as bright as it may seem in the video due to the lousy camera I used, ( trying to adjust to a dark room, and the TV being the only light source )
brightness is at about 70%, grayscale setup was done with CRT bias set to lowest & it can still produce a very bright picture, ( good sign, I guess. )

The retrace, I have never been able to fully figure out.

It was less noticeable when going via tuner, but never fully gone, and I was never able to find out why, but suspect due to weak horz blanking.
SAMS has the blanking pulse for the CTC-16(XL) @ 15v ptp, and the CTC-15 @ 25v ptp (all 6gu7)
and the CTC-20 @ 17v ptp.

The VERY BEST I ever got out of mine, ( far side of the .22 cap going to the cathodes of the y-amps ) is 9-10 , never near 15v, and I have been all over the circuit, trying to work out why it's not higher.
I don't think changing the value of the grid resistor (390k) will do any help, but what I am thinking of is changing the plate resistor (47k 2w) with a precision 3w 100k pot, to see if adjusting it may get a bit more signal out of it, but that is just an idea at this point.

Electronic M · #**372** 09-23-2019, 08:49 AM

When the circuit ain't good enough with the factory configuration and fresh parts there is either a weird problem (like current leakage in weird place like a tube socket) or it is time for decade box/potentiometer engineering...

Yamamaya42 · #**373** 09-23-2019, 10:46 AM

I did replace the grid resistor, (390k) plate resistor (47k) & coupling cap (.22) , I did see that it is very closely tied to the CRT bias switch, but I did not change any of those resistors there, cause I did not think it would have that much of effect, I do see that the cathode of the blanking amp is tied to the cathode of the bandpass, 820pf / 390 ohm paralell to gnd, these were replaced by the person who had it before me , the resistor checked OK (5% carbon film) the cap was correct, (checked by # on top)
I guess I should have replaced them too . :/

Yamamaya42 · #**374** 09-23-2019, 07:00 PM

so i guess something like... https://imgur.com/cfcsbCt could help me track down the IF failure W/O having to remove the chassis.
I'm also thinking of getting a nibbler tool to make bigger air holes in the HV case, as im always paranoid about the FBT.

Yamamaya42 · #**375** 09-26-2019, 02:32 PM

Who would have thought it would be so hard to find plug-in test adapter sockets for tubes these days.

I want to probe the voltages on the IF tubes w/o too much of a hassle, but having trouble getting the ones needed, I think I found a 7 pin, and if I have to, i'll tack wires on to a cheap 9 pin socket saver if i have to, ( no way I'm paying $50 ish for a 9 pin test socket ob ebay )