My CTC-16XL Project. - Page 9 - Videokarma.org TV - Video

Yamamaya42 · #**121** 04-27-2019, 12:51 AM

I tried to do color AFC setup and could not...
went WAY out into the weird zone when i tried...
something is really strange with the burst amp
Sams says to ground this pin , and so on...
before i go grounding anything, I want t make sure I have the right pin and that things look OK, that is where things went wrong.
Sams says 40v
I measured over 160v

something aint right!
https://imgur.com/YNdvFez
i was clipped to the leg of r10 ( it checked ok )
v22 is new, r163 seems OK, but i did not check it out of circuit.
i have not had much time to poke around it yet, but i'm not sure why the cathode voltage is so high

and i'm not about to short it to gnd until i see it in normal range... so I can't do the color AFC setup yet.

old_tv_nut · #**122** 04-27-2019, 10:21 AM

? Did you make a typo? Where is R10?

Yamamaya42 · #**123** 04-27-2019, 10:32 AM

Quote:

Originally Posted by old_tv_nut

? Did you make a typo? Where is R10?

R10 is the 1 meg color killer pot.

Yamamaya42 · #**124** 04-27-2019, 02:11 PM

OK, this just got a whole lot weirder... I seems whoever worked on this before me, ( the jerk who removed the cover off the IF board and lost it & REMOVED the color PCB... ) noticed the problem with the burst amp, and tried to fix it... because when I checked r163 and r144, they have already been replaced with metal film 2%, so I'm still in the dark as to why the cathode v is so high....

Rocket. if you ever get a chance, with your chassis in service position, and a good stable color pic, can you measure all the voltages on R10 ( color killer pot ) Sams says they should be 30 ish in voltage

Rocket · #**125** 04-27-2019, 10:02 PM

Quote:

Originally Posted by Yamamaya42

OK, this just got a whole lot weirder... I seems whoever worked on this before me, ( the jerk who removed the cover off the IF board and lost it & REMOVED the color PCB... ) noticed the problem with the burst amp, and tried to fix it... because when I checked r163 and r144, they have already been replaced with metal film 2%, so I'm still in the dark as to why the cathode v is so high....

Rocket. if you ever get a chance, with your chassis in service position, and a good stable color pic, can you measure all the voltages on R10 ( color killer pot ) Sams says they should be 30 ish in voltage

Yeah sure thing, I actually plan on throwing the chassis in for a test run tomorrow to check and see how its performing after replacing a few caps. : D

Rocket · #**126** 04-28-2019, 09:17 AM

Quote:

Originally Posted by Yamamaya42

OK, this just got a whole lot weirder... I seems whoever worked on this before me, ( the jerk who removed the cover off the IF board and lost it & REMOVED the color PCB... ) noticed the problem with the burst amp, and tried to fix it... because when I checked r163 and r144, they have already been replaced with metal film 2%, so I'm still in the dark as to why the cathode v is so high....

Rocket. if you ever get a chance, with your chassis in service position, and a good stable color pic, can you measure all the voltages on R10 ( color killer pot ) Sams says they should be 30 ish in voltage

Got them measurements while running with good color picture.
measured color killer pot, 3 terminals. 1st term closest to power supply side of chassis is 53.1, mid term 1.184, 3rd term 33.70

Yamamaya42 · #**127** 04-28-2019, 10:36 AM

If I have learned anything over the years, its never underestimate the stupidity of those who came before you.
Poking around the color pcb I have seen that most all resistors have been changed, with what looks like 1 watt carbon film, it calls for ½, and this is no problem really. I'm using ½ metal film, you can see the 2 new one I just put in in the pic, they ALSO replaced some caps, cause some disc one look new, and the person who did it, does not know how to shape leads correctly cause I see a lot of cracked meniscus, a big NO NO in my line of work, but THEN I SEE what is shown in the pic, problem with c96, and no doubt causing my voltage problem... WTF? Very careless...
https://imgur.com/YTsHAxc

Rocket, your readings are right where they should be, thanks!

Rocket · #**128** 04-28-2019, 07:57 PM

Awesome! and no prob

Yamamaya42 · #**129** 04-29-2019, 07:29 PM

Well, putting that cap in did not help, cathode voltage is still high, 135v where sams says 40v.
I'm not sure how this burst amp circuit works.
Do I ignore the fact that I see the high V on there a try to run the color AFC anyway ? Good chance it wont work.
I DO See the waveform on grid 1 as shown on sams, it looks like the lower one for color, and never changers, no matter what is on screen. 150V should be 50v horz rate Way too high I'm being flooded with horz freq?

any idea what may be doing this? I do see lines to the FBT, for what I assume is horz pulses.

Electronic M · #**130** 04-29-2019, 08:01 PM

I suspect either V22 has a short or it has a DC bias voltage issue.

Yamamaya42 · #**131** 04-29-2019, 08:32 PM

Quote:

Originally Posted by Electronic M

I suspect either V22 has a short or it has a DC bias voltage issue.

i got it "new"

i guess i can try another

Bill R · #**132** 04-29-2019, 08:53 PM

What is the voltage on pin 2 of v22? Have you changed the cathode bypass capacitor, and the screen capacitor c98 and c99? Have you checked the 255 volt source? Don't rule out a bad tube, even if it is new. Check the resistors 163 and 144 out of circuit. What about c94?

Yamamaya42 · #**133** 04-29-2019, 09:17 PM

Quote:

Originally Posted by Bill R

What is the voltage on pin 2 of v22? Have you changed the cathode bypass capacitor, and the screen capacitor c98 and c99? Have you checked the 255 volt source? Don't rule out a bad tube, even if it is new. Check the resistors 163 and 144 out of circuit. What about c94?

All resistors have been replaced before i got it wit carbon film, and just to be safe i replaced 163 and 144 again,

who ever had this before me did a lot of weird stuff to it.
I do not think c98 and c99 have been replaced, they still look old.
all bias voltage is OK, checked them when i replaced the electrolytics
I have ordered a new tube anyway.

Yamamaya42 · #**134** 04-29-2019, 09:25 PM

another potential problem
I don't know if its related to the burst amp and color killer circuit problem or the is even more problems,,,

looked at c22 ( hooked to output of 1st video amp ) feeds chroma bandpass , and good signal on the 1st video amp side, nada on the other. could be that CK is just not working right with the burst amp borked and clamping down, or its a sign of another problem :/

Yamamaya42 · #**135** 04-30-2019, 10:04 AM

Here is where things are now...
The set it pretty much in the shape as when I first got it. ( after undoing the color PCB being out ).
No color, sometimes barber-pole effect seen, unknown if it's IF related, (evidence of work done in IF PCB )
ALL resistors replaced on color PCB , except for higher power ones, some disc caps new, not sure of any else.
Apparent burst amp / color kill problem , which I am assuming is shutting off chroma bandpass, ( if I understand the circuit ) .
No video signal seen out of c22, feeding l24 ( bandpass coil ) . Saw suggestion in other thread to short point E, to force on, not tried yet.

Cathode voltage of burst amp too high, (V22) not sure why yet, all resistors new, tube “new” (another ordered) voltage starts at 20v when first turned on, and jumps to about 130v when horz kicks in.
plate/g2 voltage OK, was unable to measure g1 voltage with DVM, due to strong waveform on it ( gonna have to get my analog meter cleaned and working ) .

New, ( relatively ) v22 6JC6 coming fri, & a set of HV disc caps come mid-week, will replace c95,98,99,100 and re-test this weekend.
I hope this does something... but it may not, there may be problems elsewhere, as mentioned, I still don't fully understand this circuit yet, it seems to be a balanced feedback setup, but that is a guess.