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  #1  
Old 02-13-2003, 07:12 PM
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fredh fredh is offline
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Admiral D11 Focus

Need some help. Focus went out rather quickly. 19KV on CRT and about 2KV focus. -46v on grid. Only voltage I can find that's off is pin 7 on the H Out tube. Sams sez it sb 135. I've got 160. Replaced HV reg, damper, focus rect and H out . No change. I can't find any resistors off value in this area. Any ideas will be much appreciated.
Fred

Last edited by fredh; 02-13-2003 at 07:22 PM.
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Old 02-13-2003, 07:26 PM
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rcaman rcaman is offline
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admiral

check the focus rectifer tube socket and the picture tube socket.
they can corrode and lose connection... steve
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Old 02-13-2003, 08:39 PM
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Both sockets are very clean. The flyback was replaced several years ago and that included a new focus tube socket. I keep going back to the reg circuit but changing brightness level does not change the focus or cause the raster to increase or decrease in size. It was working quite well and then within a matter of a few hours it got progressively worse.
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Old 02-13-2003, 09:45 PM
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2k sounds a bit low.
and the socket problems are mostly breakdown/leakage or bad spark gaps.
coud be leakage between hv and focus inside the tube.
pull the socket and measure.while measuring plug it back on the tube.
should not change much if at all.
btw i have had good luck knocking out focus shorts in a crt by grounding the focus pin and lightly tapping on the neck.
if it snaps you probably got it.
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  #5  
Old 02-13-2003, 09:51 PM
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Sometimes the internal connection to the focus grid inside the CRT can fail. It's rare, but it does happen. If you have access to a CRT checker that provides this test, it might save a lot of troubleshooting grief. The B&K 467 has this function.
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Old 02-14-2003, 07:28 AM
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fredh fredh is offline
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I've got two 465 checkers but no 67. I pulled the crt plug and removed the anode. Still 19kv and 2kv. When the set was working it had 24 and 4.5. I must have missed something when I was checking components. If I did it's the FIRST time that ever happened to me. Yeah, right!. Thanks for all the input. We will find the problem. Fred
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  #7  
Old 02-14-2003, 01:08 PM
wvsaz
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You definitely have a problem in the flyback supply, including the horizontal output stage. You have already proven that the CRT is not loading it down. Voltage checks should reveal the cause. Have you checked the B+ BOOST voltage? Since you have two voltages that are low, each supplied by separate windings on the flyback through separate rectifiers, I think the problem is more likely to be in the horizontal output & damper circuits. Have you swapped those tubes?

Last edited by wvsaz; 02-14-2003 at 01:15 PM.
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Old 02-14-2003, 01:25 PM
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fredh fredh is offline
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I think so too. Pin 7 on the 6je6 is high by about 30v but I've got -46 on the grid so I think I'm getting good drive. All voltages on the osc are normal. I'm going to pull the chassis again tonight and recheck everything. I did swap those tubes and I've got 370 on the damper.
Thanks again for all the suggestions. It never hurts having other input. The fact that it became progressively worse over several hours sure does point to a component failing. I haven't check B Boost and I probably should. Vert is normal and the screens are OK as well so I just "assumed" it was good. And we know what assuming does. :-))
Fred
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Old 02-15-2003, 07:53 AM
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Found one 10k that went to 15k in the 6je6 screen circuit. That was it. Turned it back on and the same thing. I tapped the damper tube and the picture came into focus, not perfect but very good. I had already replaced that tube and knocked around in that area a lot. Not sure if it was a coincidence or something wrong with that socket. It looks fine. Still only about 20kv and now 4kv but it works and I've got some other things to do so I'm closing it up for now. Thanks again for the input. Fred
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  #10  
Old 02-15-2003, 02:34 PM
wvsaz
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Sounds like you have a mechanically intermittent connection somewhere around that damper tube.
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