CTC-16 Green Picture

[Jon1967us]

Originally Posted by DavGoodlin

Make sure the HV is adjusted so that exactly 1 volt drops across the 1K resistor in 6BK4's grid circuit when pix is dark. As brightness increases, the voltage should decrease to about 0.5-0.7 volts. Tab books' RCA color TV service manual volume 1 by Carl Babcoke explains this operation thoroughly.

HV value alone is not a good way to adjust shunt regulators, as it ignores current through the 6BK4 which is a better indicator of correct range of regulation as brightness changes. Visual check by dropping brightness to black screen while watching the cathode glow brighter in the 6BK4/6EL4 tube. That may indicate excess current.

I have found on my CTC20 Rupert that .01 mf (1 kV?) disc cap with the spark gap was leaky and allowed HV to vary so much that focus would not track with brightness. All it takes is one good and random HV snap then that cap is toast, even with a spark gap. Good luck

I have that book, so I'll take a look. The only 1k I see is the one off the cathode, which has 405v going into it. Of the screen, are two 1.5M.

The shunt circuit uses that same 405v supply as was opened in the color amps. Again, wondering if the lack of load affected it's regulation, as the focus problem crept up just as the green screen reared it's ugly head. Probably damaged the shunt circuit somewhere.

[Electronic M]

Here's a tip. If you are not well and truly done servicing it don't install the tuner/control subchassis, the 2 screws on either side of the power cord interlock are the mounts for it. If you bolt the tuner subchassis to the main chassis then all you gotta do to get it in or out is HV lead, deflection and convergence leads, and CRT socket (and lifting the chassis).

[Jon1967us]

Originally Posted by Electronic M

Here's a tip. If you are not well and truly done servicing it don't install the tuner/control subchassis, the 2 screws on either side of the power cord interlock are the mounts for it. If you bolt the tuner subchassis to the main chassis then all you gotta do to get it in or out is HV lead, deflection and convergence leads, and CRT socket (and lifting the chassis).

I remember someone mentioning that. Saw the 2 screws but didn't see how the tuner mounted on them, but now after closer examination, I see.

Note, Adjustment of focus coil produces no variation in voltage at focus pin at CRT.

[Yamamaya42]

for reference, this is what my CTC-16 looked like when i was working on getting color working and I removed the Osc crystal

https://imgur.com/9HcgQcz

[DavGoodlin]

Originally Posted by Jon1967us

I remember someone mentioning that. Saw the 2 screws but didn't see how the tuner mounted on them, but now after closer examination, I see.

Note, Adjustment of focus coil produces no variation in voltage at focus pin at CRT.

I show off the TMA feature often - 2 chassis with tuner standing on end now in my shop. I learned about it from my first employer who refused to work on any SS consoles in the late 70s. . IIRC There was a similar provision made for XL-100 and even later "jiggable" RCA chassis.

Im pretty sure Zenith has a pair of screws like that on the 66 and later models,
But yeah - like Zenith needed it. RCA had to do something if they weren't planning on putting in a $ervice $aver access panel on bottom of the cabinet

[dieseljeep]

Originally Posted by DavGoodlin

I show off the TMA feature often - 2 chassis with tuner standing on end now in my shop. I learned about it from my first employer who refused to work on any SS consoles in the late 70s. . IIRC There was a similar provision made for XL-100 and even later "jiggable" RCA chassis.

Im pretty sure Zenith has a pair of screws like that on the 66 and later models,
But yeah - like Zenith needed it. RCA had to do something if they weren't planning on putting in a $ervice $aver access panel on bottom of the cabinet

Zenith had a TMA that unplugged so it was easy to transport the chassis.
RCA, the TMA was hard wired and they made it easier to transport the chassis for service. Even the earlier B/W sets that had a separately tuner assembly had holes in the in the chassis for hanging the tuner.
The PITA was lining up the indicator wheel that was driven with the tooth belt.

[Jon1967us]

Originally Posted by Yamamaya42

for reference, this is what my CTC-16 looked like when i was working on getting color working and I removed the Osc crystal

https://imgur.com/9HcgQcz

That's good to know. You can actually see a little blue in there with the majority of green. Did the Killer work at all?

[Jon1967us]

Originally Posted by dieseljeep

Zenith had a TMA that unplugged so it was easy to transport the chassis.
RCA, the TMA was hard wired and they made it easier to transport the chassis for service. Even the earlier B/W sets that had a separately tuner assembly had holes in the in the chassis for hanging the tuner.
The PITA was lining up the indicator wheel that was driven with the tooth belt.

Honestly, even given that fact that the tuner can be mounted on the chassis, it may save you about 1 minute of labor, however it seems the real benefit is to the tuner itself, avoiding stressing all of the wires going to it.

[Jon1967us]

Originally Posted by Yamamaya42

for reference, this is what my CTC-16 looked like when i was working on getting color working and I removed the Osc crystal

https://imgur.com/9HcgQcz

Let me ask you something, did your speaker terminals break when you tried removing the lugs for the first time??

Mine did, on both of my 16s

[Yamamaya42]

Originally Posted by Jon1967us

That's good to know. You can actually see a little blue in there with the majority of green. Did the Killer work at all?

yes it did,, the main problem I had was a open osc coil, that and MANY mistakes made by the person who had it before me, bad solder work, wrong resistors, and other stuff, I was mainly working on getting color to work, and getting the IF to pass color THROUGH to the color section, that was messed up too.

that pic was taken with direct video input, I had not really done a grayscale at the time, or worked on getting the buggy b-y amp fixed at the time as well ( cooked orange drops )

and YES, the speaker lugs DID break off, which I was able to fix.

Most of the problems have been worked out, only minor annoyances remain, which I will address... someday :p