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  #16  
Old 05-11-2011, 09:17 PM
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Originally Posted by stusnyder View Post
resistance pin 8 to chassis 6460 ohm you said 6400
pin 8 to can c147 7720 ohm you said 7700
can c147 to chassis 1242 ohm you said 1300 ohm

Hmm. That rules out the divider at least. If the voltages are then wrong, it appears that something is conducting heavily when the set is running if the voltages are incorrect.

Can you provide the as measured voltages against the voltages the schematic advises? This may provide the clue.
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  #17  
Old 05-11-2011, 09:21 PM
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Hmm. That rules out the divider at least. If the voltages are then wrong, it appears that something is conducting heavily when the set is running if the voltages are incorrect.

Can you provide the as measured voltages against the voltages the schematic advises? This may provide the clue.
I can try to test some of the voltage points....if I can figure out where by the schematic...
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  #18  
Old 05-12-2011, 06:00 PM
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I can try to test some of the voltage points....if I can figure out where by the schematic...
If you look at the schematic near where the power transformer is drawn, you will see the sections of the divider resistor. Measure the junction nodes indicated with respect to chassis and provide us the readings against what it should be. For example, downstream from the 5U4 at the first node (section A of C148 elctrolytic positive it should read +215v to ground. You could measure from the focus control as that is a convenient access point.

The next point should read +135 volts to chassis.It may be accessed at C148B positive connection.

The voltage at the C147C positive should read -60 volts to chassis and the can of C147 should read -120volts to chassis.
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  #19  
Old 05-12-2011, 07:38 PM
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Originally Posted by Penthode View Post
If you look at the schematic near where the power transformer is drawn, you will see the sections of the divider resistor. Measure the junction nodes indicated with respect to chassis and provide us the readings against what it should be. For example, downstream from the 5U4 at the first node (section A of C148 elctrolytic positive it should read +215v to ground. You could measure from the focus control as that is a convenient access point.

The next point should read +135 volts to chassis.It may be accessed at C148B positive connection.

The voltage at the C147C positive should read -60 volts to chassis and the can of C147 should read -120volts to chassis.
Ok I measured directly on the divider resistor, here are the readings from right to left:
1st term (under trans) 202v
2nd term 340v
3rd term 0
4th term 15
5th term 31

measured in dc scale, black to chassis
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  #20  
Old 05-12-2011, 10:01 PM
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Ok I measured directly on the divider resistor, here are the readings from right to left:
1st term (under trans) 202v
2nd term 340v
3rd term 0
4th term 15
5th term 31

measured in dc scale, black to chassis
I assume that the DC voltages on the 4th and 5th terminals are negative with respect to chassis?

The second terminal which is supposed to be +135 volt measures 340 volts: is that correct? I assume you have changed the electrolytics. If the 135 volt line is so high, it may be that the wiring may be incorrect. Please check the wiring closely around these points.

In addition, the -15 volts and -31 volts show the correct division ratio of about 2 to 1. (It should be -60v and -120v). This would imply that the other end of the divider is open or high resistance. Otherwise something is pulling down the -120v.

Please check the wiring.
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  #21  
Old 05-13-2011, 03:06 AM
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The set is recapped, ecaps and paper caps. There was no negative readings. Checked e cap wiring many times over already.
I think this chassis has more than one problem and I won't find them all.
I have another chassis on the bench that is practicly the same thing, using as reference. That one did display a test pattern,weak and washed out, but after replacing 3 paper caps I lost it. Got a vertical problem with it now.
Ecaps were replaced.

Last edited by stusnyder; 05-13-2011 at 05:53 AM.
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  #22  
Old 05-13-2011, 08:37 PM
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The set is recapped, ecaps and paper caps. There was no negative readings. Checked e cap wiring many times over already.
I think this chassis has more than one problem and I won't find them all.
I have another chassis on the bench that is practicly the same thing, using as reference. That one did display a test pattern,weak and washed out, but after replacing 3 paper caps I lost it. Got a vertical problem with it now.
Ecaps were replaced.
Both chassis should be repairable. It is important to follo the schematic closely. Part of this game is patience and perseverence. The RCA design is more complicated than most.
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  #23  
Old 05-14-2011, 04:55 AM
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Both chassis should be repairable. It is important to follo the schematic closely. Part of this game is patience and perseverence. The RCA design is more complicated than most.
Figures I picked a real complicated one to start with. The latter one is really the one I'd like to get going, because it has a nice wooden case.
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  #24  
Old 05-15-2011, 06:03 PM
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Figures I picked a real complicated one to start with. The latter one is really the one I'd like to get going, because it has a nice wooden case.
I would be glad to help. I have owned and used an 8T243 for 42 years and have fixed a number or these chassis since. It is my favorite design.
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  #25  
Old 05-16-2011, 10:02 PM
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I would be glad to help. I have owned and used an 8T243 for 42 years and have fixed a number or these chassis since. It is my favorite design.
Are you familar with the 6-t-71? I got a odd problem with one.
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  #26  
Old 05-16-2011, 10:23 PM
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Are you familar with the 6-t-71? I got a odd problem with one.
I have worked on a few.
What is the problem?
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  #27  
Old 05-17-2011, 02:27 AM
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I have worked on a few.
What is the problem?
On the bench hooked up to a 5" test crt I get a decent picture. Back in the cabinet hooked up to the 16" crt I get no vertical lock.....
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  #28  
Old 05-19-2011, 11:42 PM
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On the bench hooked up to a 5" test crt I get a decent picture. Back in the cabinet hooked up to the 16" crt I get no vertical lock.....
Note that on the design of the kcs47 chassis that the sync take off point is after the contrast control at the video amplifier. If the contrast is reduced (less video amplifier gain) the sync amplitude is reduced. This may aggravate an already weak (problem) sync condition. Note that the kcs66 reverted back to constant amplitude sync (sync take off before the contrast control).

I assume that you have replaced the capacitors in the sync separator section? Do you have a scope to check sync amplitude? Do you notice with the test CRT if the contrast control setting is higher? Does adjusting the control to increase the contrast help with vertical sync?

Otherwise it is checking voltages, waveforms and substituting tubes in the sync section?
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