CTC5 Pickup!

[Davala]

Originally Posted by Penthode

In my Whitby I had a lot of problems with vertical sweep. The vertical hold drift I fixed by changing resistors. I found the original very temperature sensitive.

I'll be pulling the chassis again today and I'll replace resistors in the vertical section.

Did you have any trouble with the chroma section? Seems my 3.58 oscillator isn't running at all since there is zero color.

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Matt Davala

[Yamamaya42]

If it was not running, you would have the telltale greenish hues when you turn up the color, can post a pic later.

[Davala]

Originally Posted by Yamamaya42

If it was not running, you would have the telltale greenish hues when you turn up the color, can post a pic later.

Interesting.... I figured without the crystal running I would have no color. I have good greyscale tracking but zero color. If I move the hue control there is a tiny change in the grey but that's it.

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Matt Davala

[Yamamaya42]

https://i.imgur.com/9HcgQcz.jpeg


This is what My CTC-16XL was like with the crystal disabled!

[old_coot88]

When the 3.58 reference signal is missing, the chroma signal cannot be demodded in phase but only in amplitude, so it's displayed as just that yukky green color. Has to do with how the signal's phase is baselined.

[Davala]

Yay! Or maybe not yay... I found an open 6.8k 7 watt supplying B+ to the first chroma tube. R172. Above the resistor the chassis looks rather dark. I'll ohm out the transformer that connects to the plate. What the heck caused that to get so darn hot?

EDIT: I do have continuity through the transformer to plate. I do not have a 6.8k in stock unfortunately. I miss being able to buy stuff locally.

--
Matt Davala

[Yamamaya42]

Originally Posted by Davala

Yay! Or maybe not yay... I found an open 6.8k 7 watt supplying B+ to the first chroma tube. R172. Above the resistor the chassis looks rather dark. I'll ohm out the transformer that connects to the plate. What the heck caused that to get so darn hot?

EDIT: I do have continuity through the transformer to plate. I do not have a 6.8k in stock unfortunately. I miss being able to buy stuff locally.

--
Matt Davala

Power to the plate of V22 1st chroma bandpass amp, that would do it!

I would expect to find more bad resistors!

[Yamamaya42]

I can't tell for sure from the low res pics in the sams, but it may look like the set has many paper caps, and if it does many may be bad and leaky and need replacing, if C142 is very leaky, it could very well have toasted the resistor.

[Davala]

Originally Posted by Yamamaya42

I can't tell for sure from the low res pics in the sams, but it may look like the set has many paper caps, and if it does many may be bad and leaky and need replacing, if C142 is very leaky, it could very well have toasted the resistor.

I wouldn't think the ceramic cap C142 would be bad, but I have no capacitor tester. How critical is it really that I couldn't sub in a modern .01 orange drop equivalent?

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Matt Davala

[Yamamaya42]

If it's ceramic, then the chances are rather small that it's shorted, but not unheard of, the DO short, but it's really rare, as mentioned above, I could not see clearly what kind it really was, you will know rather soon if the new resister starts to heat up way to fast if something took it out like a short or something.

But if there are paper ones in other areas, best not to trust them.

[Yamamaya42]

Example, there looks to be a bumblebee capacitor on the horizontal PCB, cant see what the others are. :O

[Davala]

Originally Posted by Yamamaya42

Example, there looks to be a bumblebee capacitor on the horizontal PCB, cant see what the others are. :O

It's all been recapped... At least 45 capacitors. Wowiee. Maybe my Dumont ra-103 had more but I'm not sure!

[Davala]

I love finding former wierd repairs... I was investigating why I need more focus range so obviously I check resistors after the 1v2. The bleeder resistors were all high, they should all be 10meg. One was 16 meg, one 14 and the other actually close at 11 meg. Not an issue there as I did buy some 10meg two watts. Being NOS resistors most tested high so I found the ones closest to 11megs each. None were bang on 10, not even close. I'll get those in after I finish this post..

The former technician repair job that surprised me was the bit of wire jumping over the two 1 meg load resistors R155 and R156. I removed the jumper and tested the resistors and they are spot on 1 meg. The other bodge I found was a ceramic cap from the 1v2 cathode to ground. A bit of filtering perhaps? It looked crunchy and they ripped part of the cap where the wire leading into the cap goes. I tossed it. No value printed I could find.

Is this another CTC-7 mod they were applying or was this them being lazy because they didn't have 10 meg bleeder resistors in stock?

I'll have to wait a couple days to get the chassis back in to evaluate these issues with the focus and to see if my R172 replacement gets my color to return. I'm waiting on some .01 ceramic caps to replace the ones going to V22 as they looked bubbly and hot. I want to reduce my chances of burning out my replacement 6.8k R172 replacement.

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Matt Davala

[Penthode]

Originally Posted by Davala

I'll be pulling the chassis again today and I'll replace resistors in the vertical section.

Did you have any trouble with the chroma section? Seems my 3.58 oscillator isn't running at all since there is zero color.

--
Matt Davala

You will notice in the Deluxe chassis a high wattage power resistor dropper I recall either in the oscillator or chroma bandpass amp section. The power dissipation created a lot of heat which damaged the resistor it self and a coil. I repaired it by mounting a lower value resistor in its place to reduce the dissipation and mounted another power resistor elsewhere on the chassis in series to allow it to dissipate the bulk of the power without burning up anything around it.
You will see the resistor I am talking about. Check it is not open and if there are any charred components around it.

[Davala]

Originally Posted by Penthode

You will notice in the Deluxe chassis a high wattage power resistor dropper I recall either in the oscillator or chroma bandpass amp section. The power dissipation created a lot of heat which damaged the resistor it self and a coil. I repaired it by mounting a lower value resistor in its place to reduce the dissipation and mounted another power resistor elsewhere on the chassis in series to allow it to dissipate the bulk of the power without burning up anything around it.
You will see the resistor I am talking about. Check it is not open and if there are any charred components around it.

I'm pretty sure that's the one that went open on my set. I'll check the coil for continuity. The chassis above the resistor is definitely darkened. It's interesting the sams and rca service info differ on the value of the resistor and what B+ voltage is tapped. Sams has a 390V B+ to a 10k 7 watt resistor yet the RCA service has 300V B+ and 6.8k 7 watt. Mine had the 6.8k and I installed it closer to the chassis to help dissipate its heat better.

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Matt Davala