CTC5 Pickup!

[Davala]

So frustrating, I replaced R-172 and R-173 as they had both gone open and I still have no color. I have a good black and white image but zero color.

When I adjust the color killer I get a momentary change of hue, but still stays monochrome. Hue control does nothing. The AGC threshhold control in the rear does nothing either.

I had changed out C144, c145 and C151. I guess pull the chassis and investigate the color killer..... Hmmmmmm......

Geeze how did I miss M8? The color killer AGC diode.... Its just a switching diode and I've still got a pack of them in a drawer.

I'll replace that and check some of those resistors in that circuit.

--
Matt Davala

[Davala]

Nope that didn't do it. I did find an open 10 meg resistor connected to the color killer control. I replaced another 10 meg and two 1 meg resitors that were slightly off value. The diode was replaced although it tested fine.

Time to pull the chassis again. What a pain.

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Matt Davala

[Davala]

Tube resistance checks tomorrow! Lets hope I can find an issue I can work with.

[Yamamaya42]

This is the point where an oscilloscope would be extremely advantageous to finding such a problem.

Looking for the correct signal starting at the color takeoff coil (L36) and seeing if W23 is correct or not, (taken with color rainbow input), then onward to W24 at the color control, (bandpass 1 out), and next W25, (bandpass 2 out).

This should give some idea as where you are losing color.

[Electronic M]

The CTC-5 has all the yoke plugs at the back of the chassis so if you can find sturdy box or cooler approximately the height of the rear chassis shelf you can test the chassis outside the cabinet by setting it on a box behind the cabinet with the back of the chassis facing the cabinet.... You'll also want a clip lead between the metal parts on the CRT and the chassis....with sufficient cunning you may be able to set the chassis on its side and have access to everything while its connected and running.

[Davala]

Originally Posted by Yamamaya42

This is the point where an oscilloscope would be extremely advantageous to finding such a problem.

Looking for the correct signal starting at the color takeoff coil (L36) and seeing if W23 is correct or not, (taken with color rainbow input), then onward to W24 at the color control, (bandpass 1 out), and next W25, (bandpass 2 out).

This should give some idea as where you are losing color.

L39 primary was open. I removed the transformer ungracefully(I'll have to hot glue it back in place.. oops) and saw the issue. It is carrying plate voltage for the second bandpass amp. With such fine hair RCA used as wire it vaporized at some point in time. I should have asked my wife for a magnifying glass but I searched and saw the tiniest smidge of wire coming out of the transformer. I really had no hope of saving this transformer so I just went all out with solder and a 1 piece of copper wire. Melted the heck out of where I suspected the lead to be and after a half dozen tries I now get continuity through the primary. 8ohms just like the good book said it should be. Will it hold up? Doubtful but I tried.

Guess I'll get it back in and see what happens...

Where can I get a backup transformer? Only an RCA part number 102259, no one else made a replacement.

--
Matt Davala

[Davala]

Finally I got it. Seems my transformer "fix" is holding. Definitely seems like its drawing just a bit more power than it should at 117volts. 400-410 watts. Almost 3.85 3.9 amps...

I'm finally bringing this into the house to finish the convergance adjustments. I'd been on the ground in the garage and its very uncomfortable. My wife wants to put in in our living room replacing our 1955 B/W set we'd been using for well over a year.

I'm sure I'll be back on here soon whenever the next part fails! The set is going to cook with the back cover on.

Thanks everyone for putting up with my posts!
-
Matt Davala

[old_tv_nut]

[Davala]

The CTC-5 made it through the Hobbit DVD reliably. I wasn't sure how my bandpass transformer fix was going to hold up. Its so nice to have color and it looks so good on the 21AXP22A

The sound out of these speakers is amazing!

I'll try and not play it too much at one time to avoid stressing the flyback. Our B/W set we had in the living room would run 10 hours some days straight. I'll not be doing that with the CTC-5.

--
Matt Davala

[Davala]

Not so fast....Watching the set last night I would loose horizontal lock and was having to tweak the horizontal pretty far to get lock, nearly full clockwise. Then it would pop out of sync and I'd have to go to where it was originally set. I did this at least 4 times. Then after 4 hours I couldn't the horizontal to lock at all and the width shrunk too.

I tested the 6cg7 tube and found it had a short and wouldn't test on either section. I popped a brand new one in there that tested great. Same issue, no lock and poor width, assuming low high voltage. I pulled that 6CG7 out and it showed a short now! Thats not a cheap tube to be wasting away troubleshooting. So now I'm out of 6CG7's until my ebay order of 4 of them ships monday.

I'll do some testing in that section, there really isn't too much going on in that board. Any ideas on what would cause the tube to short out internally?

I thought this set was ready for the living room! I should have done the burn in testing in the garage.

--
Matt Davala

[Yamamaya42]

Even though the SAMS shows no cross for the RCA 102259 x-fomer, one may have been made after it was printed, and COULD be listed in a later Stancor or Merit,Triad,Thordarson, cross reference manual.

I'm sure someone out there has them and can see if any type of sub exists!

[Yamamaya42]

As for the horizontal issues, if you have not already done so, make sure there are no out of tolerance resistors in the circuit, having no VDRs in this set in the sweep area makes it prone to out of tol parts and aging more than the later sets.

Also, since parts were replaced, it's critical to go through the steps shown in the SAMS under Horizontal Sweep Circuit adjustments, this will get things most stable and lower the risk of frying the flyback.

[Yamamaya42]

OK, something is not making sense here, you put in a NOS 6CG7 and it blew right away?
You say it shorted? How, H-K?
If this is indeed the case, then you have had something critical fail in the area to cause it to push the tube way beyond it's max ratings if it shorted that fast, like an open resistor or shorted capacitor.
You should be extra vigilant in looking at every related part and finding the cause before destroying another way WAY overpriced tube, thank you audiophiles very much!

[Davala]

Originally Posted by Yamamaya42

OK, something is not making sense here, you put in a NOS 6CG7 and it blew right away?
You say it shorted? How, H-K?
If this is indeed the case, then you have had something critical fail in the area to cause it to push the tube way beyond it's max ratings if it shorted that fast, like an open resistor or shorted capacitor.
You should be extra vigilant in looking at every related part and finding the cause before destroying another way WAY overpriced tube, thank you audiophiles very much!

Thats right it caused the new tube to short out immediately. I recapped everything leaving a couple of micas. There are a few resistors there too. C-115 if that shorted it would pull the grid voltage way up. I'll swap that one and check those resistors as there are a few there.

Unfortunately, I'm away from home for a couple of days at work and then I've got to study for my yearly recurrent training early next month. I'll only be able to dedicate a short amount of time at this for a couple weeks.

A 20$ 6CG7 gone in a flash...
--
Matt Davala

[Yamamaya42]

Yeah, it's those 1k mica caps that I'm a bit suspicious of, if one or both is leaky/ shorted, it may drive the heater/cathode v way to high, you might see this on resistance checks, not sure.

But new caps are not TOO much.
82 598-CDV19EF820JO3F
330 598-CDV16FF331JO3F

Mouser parts.