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#1
04-08-2006, 04:33 AM
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621TS coming to life after 40+ years
I finally got around to starting work on this set that I got over a year ago.
After replacing some electrolytics and a few paper caps it will fire up and work as seen in the picture. Issues include: no sound, very unstable sync, vertical transformer rattles loudly, brightness control only goes from bright to very bright, electromagnetic ion trap seems to be non-functional (on 7DP4, tube used for the pic is a 5AXP4, no trap needed.) Focus control doesn't do much with the 7DP4 but the pic on the 5AXP4 is razor sharp. I've only replaced 5 paper caps so far because I'm restuffing them which is a painfully slow process but will keep the appearance original top and bottom. Each capacitor replaced has made a noticable difference in the performance however. One paper cap attached to the Horiz output tube had never been soldered, just wrapped around the post! (see pic) Wonder if that had ever given them problems? Last edited by Eric H; 04-08-2006 at 01:21 PM. 
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#2
04-08-2006, 09:38 AM
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Wow, re-stuffing cap in a '621! I am impressed. Too bad they never made a 7AXP4. Keep up the good work!
__________________
John Folsom
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#3
04-08-2006, 01:27 PM
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Quote:
This is an Aluminized tube that can be used to replace the 7DP4 http://www.earlytelevision.org/7dp4_replacement.html
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#4
04-08-2006, 07:31 PM
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Excellent! Wish I could find one of those.
I don't have the patience to restuff paper caps on a TV -- too many! This should inspire me to get off my duff and finish my 630TS, which now has a fantastic picture but no sound.
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#5
04-08-2006, 09:44 PM
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Progress
Well, I spent the afternoon stuffing another 6-8 caps and checking out some of the problems this set has/had.
Got the sound working, it has a bad connction somewhere under the 6AT6, possibly a bad tube socket since there is a lump of solder on the #7 pin like someone had been trying to fix this before. The sound is working now after I tweaked the wiring around a little, though I'll have to do a permanent repair when I change out the caps on that tube. The focus problem seems to be bad resistors in the focus divider circuit, they have drifted up beyound the 20 meg capacity of my meter. (brown/red/blue is 12 meg ain't it?) If I jumper across one of the resistors to compensate I can get a nice sharp focus on the original 7DP4. The sync is pretty stable now after changing out some more caps in the oscillator circuits, the video and sound are so good I may leave the i.f. caps alone, or at least change them one at a time to make sure I'm not screwing up anything. Looks like i'll need a vertical output transformer, this one works but will drive me nuts with all the noise it's making! Anyone know if the 630 uses the same transformer? I posted a video of the working chassis here: http://www.vintagetvsets.com/videos/621.wmv the buzzing noise you hear is the Vert transformer! 
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#6
04-08-2006, 09:53 PM
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P.S. Ion Trap.
The Electromag Ion trap still doesn't work, it might just be open but I don't know where the wires connect to to test it.
Looks like they might go to those big resistors inside the black box on the back? Would anyone have a schematic for this set they could scan? Sams #78 which I think it's just a single sheet schematic not a complete Photofact.
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#9
04-09-2006, 07:42 AM
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Eric,
When you say the ion trap isn't doing anything, is that on a actual 7DP4 or your replacment from Fair? The aluminized tube from Fair will not require the ion trap, only the non-aluminized original 7DP4 will. Keep up the good work! Darryl
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#10
04-09-2006, 09:27 AM
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Eric, The vertical output xformer IS the same in the '630 and '621. Stancor A8115, Thordarsen 24S86.
__________________
John Folsom
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#11
04-09-2006, 12:08 PM
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Steve, thank you for the schematic, that will help a lot!
Darryl, yes, I can't get any raster on the 7DP4 using the EM trap, there is no magnetic field that I can detect, I'm using a PM trap for now. John, thank you for the info, I have a junk 630 that may have a good transformer! Eric
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#12
04-28-2006, 10:27 PM
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Getting close to done!
Whew, restuffing caps is a huge PITA but I'm almost done, just one two-section filter left.
I encountered a problem with the sound getting into the picture, the louder the volume setting the more the picture would jump and dance, you can see traces of this in the video i posted but it got a whole lot worse! Turned out to be a leaky four-section can causing the problem, I found a NOS Mallory on eBay that was close enough because I didn't want to try and stuff a 4 part cap  Here's some before and after pics, the caps are cleaner and not covered in wax anymore but they basically look the same. I like that at first glance it looks original 
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#14
04-29-2006, 07:31 AM
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Quote:
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Linear Mode
