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Old 01-25-2018, 01:06 AM
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Jon F Jon F is offline
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RCA CTC-16 Lost HV after cleaning/testing tubes

Hi all, I was working on my RCA CTC-16 cleaning and testing tubes and turned the set back on and I lost HV. Watching the cathode current at the 6EJ6 it starts around 200ma then shoots off the scale and the tubes start to overheat so I turn the set off

Before I did this the set powered up fine, no color, but still worked OK. I've re-checked the tubes, substituted them, made sure they are in the right socket, etc all the basic stuff.

The tubes I messed with before the issue: 6JE6 horz output, 6DW4 damper, 6GF7 Vert output/osc, 6FQ7 Horz orc, 6KA8 AGC noise/sync sweep.

I'm not sure what I did but maybe someone can point out something I missed? Also, electrolytics have all been replaced. Tubes have all tested OK.
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Old 01-25-2018, 04:49 AM
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Possible broken tube socket pin , or what's attached to the underside of the socket pins.
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Old 01-25-2018, 08:12 AM
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DavGoodlin DavGoodlin is offline
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Check the terminals on the horizontal waveform coil next to the 6CG7, just a bit of jostling on the board nearby can expose a cold solder joint
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Old 01-25-2018, 08:48 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by DavGoodlin View Post
Check the terminals on the horizontal waveform coil next to the 6CG7, just a bit of jostling on the board nearby can expose a cold solder joint
I would be a good practice to go over all the tube socket connections on both the front AGC, vert and horiz board. Also go over the ground connections on both boards and the rest of the tube sockets.
Another important area is to look over two wires that are on top of the color board around the 6GU7's. They corrode and crumble from the extreme heat. Remove them and relocate them to the bottom of the board.
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Old 01-25-2018, 12:46 PM
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Electronic M Electronic M is offline
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Odds are you lost grid drive to the h output tube. Check grid voltage to confirm.
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Old 01-25-2018, 01:18 PM
old_coot88 old_coot88 is offline
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The two ground stakes on the far right end of the chroma board need to be re-flowed on every CTC-12, '15, '16, '17, and '25 chassis. They go open and kill the heaters on the 6GU7s.

Although probably not related to the problem at hand, those joints should be reflowed as a matter of routine.
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Old 01-25-2018, 01:27 PM
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Eric H Eric H is offline
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Make sure you put the correct tube in the horiz oscillator socket.
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Old 01-25-2018, 02:35 PM
RVonse RVonse is offline
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Quote:
Originally Posted by Electronic M View Post
Odds are you lost grid drive to the h output tube. Check grid voltage to confirm.
+1 This

and this..
Quote:
Originally Posted by Eric H
Make sure you put the correct tube in the horiz oscillator socket.
As an added aside, make sure you do not run the set this way with no horiz oscillator to the 6Je6 grid. Or the 6je6 plates will be turning red with run away max current. You will very soon be ruining that tube as well, if you haven't already toasted it.
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Old 01-25-2018, 08:01 PM
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Jon F Jon F is offline
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Wow thanks for all of the quick feedback! I haven’t been running the set longer than a minute or so since. I’ll check out the suggestions and reply back.
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