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Tom Schulz
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 5:36 am |
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Joined: Mar Sun 01, 2009 10:27 pm Posts: 2915 Location: Ann Arbor, MI
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That last picture looks like the picture is just not centered. Do try the centering rings. The earlier picture showing a vertical black bar with video on both sides was not a centering problem.
_________________ Tom
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 3:00 pm |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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I think I get it now. IF you had a good solid lock and the only issue before was centering, and IF you tried to center with the horz, THEN you could end up with a phasing issue that looks like one of your early pics. That would have been at the extreme end of the horz just before it breaks lock. I was assuming the out of phase condition existed all the time, but if you were forcing it out of phase in an attempt to center then it all makes since.
I agree with Tom the last pic is just needing centering with the rings.
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Johnnysan
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 3:47 pm |
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Joined: Jan Thu 01, 1970 1:00 am Posts: 11441 Location: Albuquerque, NM 87123
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A centering ring problem doesn't make much sense. In your first post you state that it worked OK for a few days. Unless someone moved the rings this should not be your problem.
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 4:11 pm |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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Regarding the interaction of the audio, I notice it uses the audio out as a voltage divider. Make sure the C4 and C3b eletro is good.
check the 130v supply voltage. May have something to do with the oddness in the contrast circuit. the Screen from the video out is supplled by that 130v.
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 6:32 pm |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Dave, I think you just solved it for me. C3B is the only electrolytic I didn't replace. Assuming it was tied into the audio, I left it alone since the audio was fine. I did replace the other sections of C3 and C4. I just checked the 130V source which is pin 1 the the 12CU5 audio output tube which has C3B and C4 coming off of it. With min vol, I get about 125V, and the pic is stationary. Raising the vol causes the voltage to drop and that vertical line to appear at the right side of the screen. As the vol in increased, the bar continues to move towards the center of the screen, and the voltage keeps dropping to about 76V at max audio. I'll replace C3B tonight and hope that fixes the problem.
Doug
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 7:03 pm |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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if not try a new audio out as well. Those stacked B+ power supplies can be sneaky. I see it also supplies the 2nd IF and the tuner.
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Tom Schulz
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Post subject: Re: Another Admiral with horizontal issues Posted: May Tue 01, 2012 8:22 pm |
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Joined: Mar Sun 01, 2009 10:27 pm Posts: 2915 Location: Ann Arbor, MI
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Also make sure you replaced the capacitor that couples the audio into the grid of the audio output tube.
_________________ Tom
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Wed 02, 2012 3:34 am |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Well replacing the 60fmd electrolytic helped some but not enough. With the new cap in I did some voltage checked on the 130V source line: At startup, as soon as the pic comes on, I get 80V and poor contrast. Turning up the vol makes the pic pull to the left. After 30 more seconds I have 100V, and the contrast is better. After about 2 min, the voltage has climbed to around the 125V range, and the pic is somewhat stable. If the set stays on for about 30 min, the source voltage will climb up to around 145. The more it plays, the less stable it gets. As far as the centering rings, I think what happened was the cover of the yoke came off at one time while I was removing the CRT, and I probably didn't get it back on right. I went all the way around with the cover which moved the rings all the way around. The best I can get it has all but the bottom edge of that vertical bar gone. Tom, I did replace that 330 capacitor on the grid of the audio tube tonight as well. Doug
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Wed 02, 2012 2:01 pm |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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You need to check the .001 that goes from the volume pot to the grid. If that one is the slightest bit leaky it will upset the tube bias and really goof up the voltage drop across the audio out. check the grid voltage and see if it matches up. You should use a VTVM for this as that is prob what was used back when the voltages were noted on the sams. A DMM is prob close enough, but not a analog VOM.
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Wed 02, 2012 2:59 pm |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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also if you have another audio out tube try subbing that.
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Wed 02, 2012 5:44 pm |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Dave, are you talking about C38 which is a 10000 mmf on the Sams?
Doug
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Thu 03, 2012 2:36 am |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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sorry cant seem to see the schematic right now, but its the one that comes off the center tap of the VC to the grid, I thought it said 1000mmf but I may have just read it wrong. 10000mmf (.01mf) makes since. The issue is if it leaks and had B+ on one side, then DC would come across and put a positive bias on the grid, causing issue with the voltage drop. ah the pdf finally loaded yes its C38 and it is 10000mmf (.01uf)
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Thu 03, 2012 2:54 am |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Dave, I had figured that capacitor was a .01 instead of a .001, so I replaced it this evening. I then fired it up and let it play for about an hour. The pic did lose sync one time. I just let it cool down for about 30 min and just turned it back on. It takes about 2 min for that voltage to reach 130V. The pic seems pretty stable, but I still notice the edge of that vertical bar at the bottom of the screen. While I was sitting in front of it (the set had been on for about 2 1/2 min) our central A/C kicked on which made the pic jitter and lose hor sync. I'm gonna let it play for about 30 min and see how it does.
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Johnnysan
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Post subject: Re: Another Admiral with horizontal issues Posted: May Thu 03, 2012 6:05 am |
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Joined: Jan Thu 01, 1970 1:00 am Posts: 11441 Location: Albuquerque, NM 87123
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If it takes 2 minutes for any B+ line to reach proper voltage then you still have a problem.
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Thu 03, 2012 2:57 pm |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Thanks for the tip Johnny. After the set plays for about 30 min or so, the B+ goes up to about 145-150. What I will do is take everything off the B+ line and start connecting thins back one at a time until I find what's causeing the charging time to take so long.
Doug
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Tom Schulz
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Post subject: Re: Another Admiral with horizontal issues Posted: May Thu 03, 2012 10:44 pm |
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Joined: Mar Sun 01, 2009 10:27 pm Posts: 2915 Location: Ann Arbor, MI
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Have you tried another audio output tube?
_________________ Tom
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Fri 04, 2012 1:31 am |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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No, I haven't tried another 12CU5 yet because I don't have a spare, unless I dig into one of my other 2 metal cabinet Admirals. It may come down to that though. I did check it last night, and it checks ok. Today I took loose all of the wries coming from the 130V source. To me, what seems to be dragging it down is the wire going to the PC bioard. That wire supplies the B+ to pin 8 of the 6BA8A wideo output tube. I went ahead and replaced C29 (10000 mmf) on that line, but that didn't help.
One thing though: I checked the voleages on the 6BA8A, and all were normal except the plate. It SB 155V, and I have 245V.
Doug
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Sun 06, 2012 1:36 am |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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did you check the voltage with no signal?, plus you can't always trust SAMs. I dont think that would effect the horz anyway, If the pic looks good, has good brightness control and contrast control the the video out is prob fine.
If the horz is at fault (not a centering issue) and the normal stuff is not fixing it (diodes and other horz AFC parts good, tubes V5, V6, and V10 have been subbed, then last thing before the scope would be check the pin resistance charts for those same tubes. If all that checks then then you need a scope to look at the sync pulses to the AFC and see if there is any problems.
It looks to me like the horz is just set too far out in an attempt to overcome a centering issue, but its hard to analyze with out being able to actually see the pic and how the adjustments effect the pic.
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DaveM
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Post subject: Re: Another Admiral with horizontal issues Posted: May Mon 07, 2012 4:20 am |
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Joined: Aug Thu 07, 2008 1:36 pm Posts: 2067 Location: Orlando
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one last thing, the 3900mmf across the horz coil. If you have an eye tube checker you can check the caps, rather than replacing to check.
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Doug66
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Post subject: Re: Another Admiral with horizontal issues Posted: May Mon 07, 2012 2:08 pm |
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Joined: Mar Wed 30, 2011 5:37 am Posts: 596 Location: GA
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Dave, I fought with it again over the weekend.
I did find another 12CU5 tube for the audio B+ as Tom suggested, but that didn't help. I did play around with the 5600 ohm resistor coming off the horiz coil by changing values up to 6800 and down to 4700ohm. All that did was cause me to have to adjust the horiz coil to a different spot, but the pic was still not centered.
I already replaced the 3900 mmf capacitor. I've got an EICO capactior checker with an eye tube, but I went ahead and replaced the capacitor. The coil is checking at 100 ohms like it should, but I am going to replace it. I found one on ebay last night, so it should be here by this weekend. I've replace everything else, so the coil is about all that's left.
Doug
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