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-   -   What could Account for This? RCA 9TC-240 Power Issue (http://www.videokarma.org/showthread.php?t=276754)

Chris K 07-31-2024 09:21 PM

Flyback tests fine

Yamamaya42 07-31-2024 09:22 PM

Quote:

Originally Posted by Chris K (Post 3258543)
15 ohms on the horizontal yoke. I measured from pin 6 of the 5V4 damper to the other side.

That is well within tolerance, the problem must be some place where the yoke hooks to, a bad cap or resistor, or solder joint.

Chris K 07-31-2024 09:28 PM

Yes the solder joints in the HV cage do look terrible so I'll go through them tomorrow. I don't like soldered in fuses much. I'll add a fuse holder for the 0.25 amp fuse as well. Headed for bed. Thank you guys so much. We'll get it run down.

Yamamaya42 07-31-2024 10:38 PM

one side of the horizontal part of the yoke goes to the plates of the damper tube, the other goes to a power point same as the focus coil it look like.

Chris K 08-01-2024 08:51 AM

Yeah the RCA schematic for the 240 is drawn out differently than the Sams. The fuse is directly in line with the yoke and pin 6 on the 5V4 is on the other side. I also ohmed it out from the focus control. I got 13.5 and 15 ohms from multiple places and I doubt a reading that close to the actual value from 2 spots is a coincidence. But with my luck, it could be! I need to get into the HV cage and do a complete service. Haven’t done anything in there yet. Need to resolder and clean and check values.

Chris K 08-01-2024 05:43 PM

Gettin' Closer
 
OK, I know why there's no horizontal deflection. It grew out of working with multiple schematics from various models, direct replacement of capacitors in the chassis, value for value, and confusion regarding the Sams chassis photos of the bottom.

This chassis had a number of those weird caps in it...not waxies but almost like a cylindrical ceramic with coding stripes, in fact, they look like giant resistors only light in color. I can't replace these value for value because I can't read them (color blind). I depend on the sams photos to identify color coded stuff like this.

The problem with the horizontal yoke is that one side isn't connected. If you look closely at the picture, you can see the thick yoke wire attached to the highest lug of the bottom terminal strip. There was one of those funky caps attached to it running down into the terminal strip that has the large 0.47uf cap soldered in. The sams photo does not have the cap I cut out pictured.

https://imagizer.imageshack.com/v2/1...922/xBGJwK.jpg

You can see the yoke lead soldered to the terminal but there's nothing attached to it after I cut out the mystery cap

Here is a wider view. The striped lead running horizontally across the center goes to the yoke. The large diameter yellow modern cap is the 0.47uf I put in to replace another large old cap...but not the one I previously cut out. It is C199 in the schematic down at the end.

https://imagizer.imageshack.com/v2/1...924/BrvumL.jpg

Here is the section of the schematic I'm using. The sams is depicted so differently.

https://imagizer.imageshack.com/v2/1...924/MC6Jmf.jpg

So, I need to connect the yoke lead to something. Like I said, someone has been in here before so I'm not sure what I saw when I opened it was what rolled out of the RCA factory. The other side of the horizontal yoke is connected in the HV cage fine.

Yamamaya42 08-01-2024 06:15 PM

so that must be the .047 cap on the RED/BLACK wire to the fuse line that is missing, it gets hit pretty hard, not sure what DC rating is called for, must be rather high.

this is prob overkill. but..
598-474MWR102K mouser part.

bandersen 08-01-2024 06:49 PM

Those caps you describe are simply paper caps inside plastic like bumblebee caps.
I'm confused - you say the .47uF cap pictured is C199?
This is the one that connects to the yoke. What do you have it going to?

bandersen 08-01-2024 07:04 PM

There are two .47, 200v volt caps in this set. C190 and C199 in the RCA service info. One is used for AGC the other is for the yoke .

Check out the RCA wiring diagram. C199 is located in the middle at the bottom.

The yoke connects on the left side of C199

https://live.staticflickr.com/65535/...bf79f89a_z.jpg

Chris K 08-01-2024 07:10 PM

C199 on the schematic picture I posted. Lemme take a look at this. I did not have a cap bridging those terminals when I started.

Yamamaya42 08-01-2024 07:11 PM

Yeah, i was a bit perplexed too, not sure if the cap in question is just missing, or just in the wrong place. :scratch2:

I'm just a bit surprised it got any HV without it! :D

Chris K 08-01-2024 07:12 PM

The schematic pic posted is from an RCA publication specifically for 9TC-240 model

Chris K 08-01-2024 07:20 PM

I think the WD I'm using is a bit different. Same values but different component numbers

https://imagizer.imageshack.com/v2/1...922/GwzX7c.jpg

bandersen 08-01-2024 07:25 PM

That's weird. The one I posted is specifically for this model too - KCS28B model 9TC240

bandersen 08-01-2024 07:26 PM

Quote:

Originally Posted by Yamamaya42 (Post 3258560)
Yeah, i was a bit perplexed too, not sure if the cap in question is just missing, or just in the wrong place. :scratch2:

I'm just a bit surprised it got any HV without it! :D

Not surprising at all. It just means the yoke is disconnected. The HV comes from an autoformer on the primary side.


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