|
|
|
#1
07-22-2004, 01:05 AM
|
||||
|
||||
|
My Hallicrafters lives!
Hallicrafters Model 820
This is the one I scored in Powell, OH this past December. The seller did the evil rotten "plug it in and try it." He reported a loud hum at all volume levels. I did a proper soft start and confirmed the filters were all bad. Forward to now. I did a full recap. The tube lit up nicely and the horizontal was slightly off (adjusting the coil did it). I do have severe vertical foldover, so I'm not ruling out the possibility of bad resistors or putting in a wrong value cap. There are the before pics posted to my site. I had to eliminate one of the filter cans completely since the replacements would not fit, plus, if I added a terminal strip, I could eliminate some of the clutter underneath. I chose the easy way. The other cap was restuffed with two of the three values. I'll keep you posted here and on my website. Here is a crappy vidcap of the set when I got it. 
|
|
#2
07-23-2004, 09:19 PM
|
||||
|
||||
|
I rebuilt the couplate between the sync clipper and vert oscillator and solved the linearity problem, but the vertical hold will not lock. I can get it slowed down. Are the cap values in this couplate critical? I used 5600pf caps, as I couldn't find 5000pf. Any suggestions are greatly appreciated. I should have about -25 on the control grid of the oscillator and am only getting -12. The minimal voltage at the plate should be from 105 to 250. I get less than 100 (varies between 50 and about 80). I am getting some ideas as of this writing and will post what I find.
|
|
#3
07-23-2004, 10:47 PM
|
|||
|
|||
|
Yes the values of the capactors will be critical in that network.Also did you check the components for the vertical feedback???Also check the resitors around the vert. osc tube.
|
|
#4
07-23-2004, 11:17 PM
|
||||
|
||||
|
I GOT IT!
I disconnected the ground wire from the new couplate and the picture locked, but with some jitter. Then, I experimented with various value resistors from that lug to ground. A 22K locked the picture in solid. Technically, the chassis is now not original due to this modification, but it works. Tomorrow, I'll do the rest of the "smoke test" (that is, I'll play it out of the cabinet for a few hours. If it doesn't go up in smoke, I'll take after pics and put it back in the cabinet). I did not find anything goofy in the other related circuits. It had some 1M resistors, which I thought had drifted, but they didn't. My thanks for confirming my suspicions about the cap values in the couplate.
|
 |
|
|
Linear Mode
