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  #61  
Old 10-03-2012, 07:09 AM
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Charlie Charlie is offline
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Yeah that yoke plastic sucks, doesn't it?! I've got a few sets that have that issue... or simply a lack of plastic to hold it all together in there. I notice that Motorolas of that time period seem to always have this issue (as well as Motorola knobs).

Bob has section covering this on his site at http://antiquetvguy.com/Web%20Pages/...okeCovers.html
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  #62  
Old 10-03-2012, 07:06 PM
DaveWM DaveWM is offline
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all tubes checked on the chassis, did not check the tuner tubes, and did not replace any paper caps on the tuner (I think there is one). So hopefully I will be able to do that tomorrow, then maybe Sat I can give it a try

I replaced the one 6EA8 with the slight short and a 6LF8 that was shorted a bit harder.
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  #63  
Old 10-06-2012, 05:14 PM
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got raster, then pic and audio, but the pic looks like its got an agc issue or a sync sep issue, (vert and horz sync are soft). HV is right around 20kv but that is thru a 100ft cord AND a isolation trans that can barely handle 3amps, so I am hoping at full line voltage it will be up a bit. I did not see if the HV adj did anything. the tuner has a paper cap so maybe that is an issue, I presume its an AGC filter cap. I will start by replacing that. I did not fiddle with the AGC pot so of course that could be it as well. If neither of those work out I will try a composite video feed. I need to back and review the AGC setup.

Its coming along...
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  #64  
Old 10-06-2012, 06:25 PM
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hmmm I seem to recall cleaning the pots up front, so I bet I just need to reset the noise/agc, but too tired to fool with it any more, so back on it tomorrow.
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  #65  
Old 10-06-2012, 07:05 PM
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AGC pot has no effect what so ever. So I think I will start with a simple AGC bias and see if that clears it up. If so I will dig into the AGC circuit. I just hope its not a feed back pulse from the fly back that is missing.
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  #66  
Old 10-06-2012, 07:30 PM
DaveWM DaveWM is offline
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Even though the bias did not seem to work I still think its got to be in the AGC circuit, just cause the agc pot did nothing. But will get the scope out and look around. will start at the plate of the AGC tube looking for the keying pulse. Will also look to see what the signal to the sync sep looks like going in and coming out. I suppose the smart thing would be to try new tubes there 1st.
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  #67  
Old 10-07-2012, 01:15 AM
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wkand wkand is offline
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CTC% Resto _ Skinny Brown Electros?

Hi Dave:

Where did you get the skinny electrolytic caps you used to replace the former FP cans? I've never seen high volt electrolytic caps like that before.
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  #68  
Old 10-07-2012, 08:35 AM
DaveWM DaveWM is offline
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Its a new cap that mouser carries. They work great for inside can stuff.
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  #69  
Old 10-07-2012, 08:37 AM
DaveWM DaveWM is offline
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I have been thinking about it, I am betting its something to do with the noise inverter. The agc does something just not much, and if the H sync is off, the AGC is of course not going to work right since the keying pulse will not match up with the sync tips.
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  #70  
Old 10-07-2012, 01:26 PM
DaveWM DaveWM is offline
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put a new 6U8 in place of the 6EA8 that was there, (sync sep) fixed the sync and now the AGC works as it should. Only thing left is to setup the purity (screen colors are all over the place with HUGE convergence issues), but its coming along.
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  #71  
Old 10-07-2012, 01:32 PM
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I did not even touch the convergence magnets so that should help some, but I still need to fix the yoke plastic AND move the CRT to the new cabinet.
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  #72  
Old 10-07-2012, 02:20 PM
DaveWM DaveWM is offline
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oh so there are no PM for static, instead there is DC pots, thats something new to me. I can see how this should be easy to setup with evey thing out front.
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  #73  
Old 10-07-2012, 04:24 PM
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old_tv_nut old_tv_nut is offline
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Quote:
Originally Posted by DaveWM View Post
oh so there are no PM for static, instead there is DC pots, thats something new to me. I can see how this should be easy to setup with evey thing out front.
Good luck on the pots - all three were burned open on mine, and 2 of 3 someone gave me from a donor chassis were also. These are special 100 ohms tapped at 25/75, esentially unobtainium. It was a poor design since this is at the low end of what carbon comp pots can do resistance wise.

The problem is that the tap is used to set up a zero-current point so you can go plus or minus. The only way I could get it to work with an untapped pot was to use two pots with a toggle switch to select if you wanted zero to plus or zero to minus. It seems like it would be easier to use the convergence coils from a later set with the permanent magnets, but I think they are wired differently for dynamic convergence too, so won't just drop in.
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  #74  
Old 10-07-2012, 04:31 PM
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contrast was a bit low, I had a new video out tube already, so a new 1st video amp and now the contrast is very good, can go from little to too much now.

I was trying to set up the purity so tried sliding the yoke back, and killing the green and red grids with 100k resistor to ground, when I powered it up, no HV. Popped a 3/4 fuse. My guess is I must have shorted out the yoke somehow. I monkeyed around with it some more and tried a new fuse, and got it back. I adj the purity and slid the yoke forward, got a nice full red screen. I am not sure what happened on the yoke but I will not mess with it again until after I have moved the CRT and fixed the plastic. I have a spare yoke so will experiment with it on making up the plastic piece. that way I can keep working on the set while getting the spare yoke ready to go. The center convergence is pretty good now, but the dynamic is still way off.

I have not yet tried adjusting the eff coil for lowest current. IIRC the service manual has you checking the voltage drop across the cathode fuse. I think I will just use my fuse adapter and plug that in with the current meter in place of the fuse to dip the cathode current.
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  #75  
Old 10-07-2012, 04:33 PM
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I have a donor chassis as well, so hopefully I can get it right. but since the center is looking good I may be ok.
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