#61
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Wouldn't worry about it too much, long as the dag on your crt is in good condition it'll have way more capacity than the doorknob anyway.
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Evolution... |
#62
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The Dag is very good. Thanks.
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#63
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#64
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Well, I decided to re-stuff my doorknob cap. I ordered 10 ea 470pf 20Kv caps from eBay for $6 shipped. http://www.ebay.com/itm/282085716087...%3AMEBIDX%3AIT
I cut off the bottom end right at the bottom portion of the main body. See the red arrow. I used my trusty band saw and took my time. No room for error. Here is a picture after the bottom is cut off. I then used my Dremel with a Robart 3/8 ball carbide cutter http://robart.com/collections/hobby-...-8-ball-coarse to grind out a cavity to house the new cap. I kept at least a 3/16 edge so there will be room for the epoxy to glue to when gluing on the bottom. I ground down till I can see the copper end post. I then used some flux and solder to coat each end till my caps arrive. More to follow when the caps get here. Last edited by Crist Rigott; 02-25-2017 at 11:07 AM. |
#65
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Yeah, doorknobs came into use with metal cone CRTs which needed the extra filtering. When all-glass CRTs with internal/external aquadag came along, doorknobs kinda got 'grandfathered' along for a while, though not strictly needed.
Last edited by old_coot88; 02-25-2017 at 06:11 PM. Reason: TYPO |
Audiokarma |
#66
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Yeah, I know they are not really needed on this set. I'll re-stuff this one and reinstall for authenticity.
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#67
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So what was inside this thing? Silver Mica?
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#68
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Metalized ceramic usually.
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Evolution... |
#69
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Just a little grey but mostly powered phenolic.
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#70
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I would be leery of re-using that casing because of leakage concerns.
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Audiokarma |
#71
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Why? When I solder in a new cap where will it leak?
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#72
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Now that the innard's exposed to ambient air/moisture, seems like it'd be prone to corona and arc-over inside. Or maybe I'm just being a fuddyduddy.
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#73
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Maybe you are. But we will see together when I get the caps in.
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#74
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I reassembled the TV to power it up. As a recap of what was done so far, was to replace the E-Caps, clean the on-off volume pot, clean the brightness contrast pots, clean the V and H hold pots, clean the focus pot, replace some caps and resistors.
I powered it up using my variac and all seemed good using my 5AXP4 CRT. (EDITT: I then installed the 7DP4 CRT.) After a little warm up, I adjusted the Ion Trap and had a very bright raster. The HV is good! I could hear good audio from channel 6 a local FM station, but when I had a good picture from my converter box, there was no audio. I could hear static and some clicking. A lot of hash when I changed channels. I haven't gone through the audio section yet. Over all a decent picture and good audio but not together. Of course I have a lot of caps and resistors to replace. I'll do some more power ups as I go through each section. And I haven't even touched the tuner yet. Here is what I have now: A composite of before and after: Last edited by Crist Rigott; 02-27-2017 at 09:54 AM. Reason: Clarified when I used the Ion Trap. |
#75
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Hi Crist,
You said you heard clicking? Does it sound more like ticking, intermittent or continuous? I ask because if you stuffed the old doorknob with a modern ceramic or mica cap, you may have arcing between the cap leads. When I repaired my Admiral last fall I used a 15kv cap as a substitute for the old doorknob. When I first tested the set I would hear ticking. Lowering the brightness would increase the amount of ticking, increasing would decrease the amount. I had to operate the set on its' side and in darkness to see the source of the ticking. Turned out the gap between the capacitor leads right at the body of the cap needed a greater gap. The proper dressing of the leads solved the problem I had. I didn't reuse or stuff the old doorknob. I mounted the cap under the chassis. Ed |
Audiokarma |
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