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#76
10-13-2015, 01:28 PM
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Okay, looking at various tube diagrams, it seems that holding the tube so the gap is at the 6 o'clock position, pin 1 is always on the left. So going by that logic I connected leads to pins 2 and 12, and get about 2 ohms. (Just saw the updated post, and did pins 12 and 1 too, same reading)
I think the tube is good. Now, Electronic M mentioned that the horizontal output tube could also cause HV loss, as can a bad damper tube. Before I totally lost picture, I did remove and reseat the horizontal output tube (I mistook it for the rectifier tube) and the damper tube (mistook it for a shunt regulator... yeah I know...) Can i do a continuity test on these tubes as well? Last edited by MRX37; 10-13-2015 at 01:37 PM. 
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#77
10-13-2015, 01:36 PM
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yes, but that doesnt tell you much, if the tubes light up, the heaters are obviously good.
more informative would be measuring the voltages on the tubes, to see if they are in the ballpark. Trouble with those stages should show up in weird readings. Folks on here should be able to interpret the results and tell you what to test next. A good filament also does not mean a tube is good overall. Just that the filament is OK. all the stages in the horizontal section, HO output tube, H. Oscillator, Damper, and HV rectifier all work together to generate HV, and all stages need to be within spec. One leaky cap or shorted flyback winding can kill the picture, or let out smoke...
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#78
10-13-2015, 02:22 PM
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UPDATE:
 This is why I didn't have a picture! Must have knocked it off when I reseated the Horizontal tube! Picture's back, but it's still bloomed out. Horizontal tube is obviously good. Where do I go from here? Edit: decided to test B+ again now that the yoke was connected properly, and it actually went up slightly. It's now in the 265-267 range which is where it's supposed to be. I guess unless you guys can think of something else, I'll see about procuring another 3AT2 Last edited by MRX37; 10-13-2015 at 08:54 PM.
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#79
10-19-2015, 07:53 PM
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Quote:
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#80
10-19-2015, 08:11 PM
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Quote:
if packed well, tubes travel just fine via post office. I received a 12HLT today from California and it made it fine.
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#81
10-19-2015, 08:32 PM
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Quote:
Like I said I have quite a few of those 3AT2 tubes in my tube caddy and probably will never use them and as far as I know they're NOS tubes.
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#82
10-19-2015, 08:35 PM
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Quote:
If it's an irregular shape, it might a yoke problem. As a result, the set will not produce sufficient high voltage. 
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#83
10-19-2015, 09:00 PM
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I think the no signal box looked very slightly distorted. Attached is a picture of it. It's about twice as big as it should be.
Also noticed that when turning the brightness knob up, the image blooms out even more and shrinks when i lower it. Definitely low HV. question is... is it a bad rectifier tube, a bad damper tube, a bad flyback or a bad yoke? Or something else?
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#84
10-19-2015, 09:21 PM
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Quote:
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#86
10-20-2015, 08:33 AM
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many years ago NEVER say 100%. You can 99% eliminate yoke, FBT. Tiny chance its the damper or hoz out. H out are almost always VERY expensive. 73 Zeno 
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#87
10-20-2015, 08:40 AM
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Oldcoot 100% on this. DO NOT draw arcs to ground.
The ONLY time to use ground is to discharge the CRT with the set UNPLUGGED ! And not at the plate cap. That wont work. Go under the anode button. 73 Zeno Quote:
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#89
10-24-2015, 11:59 AM
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Thanks to a generous donation from Captainclock, I received a new 3AT2 tube, AND a tube tester!
 Put in the new tube, and it seems to have solved the problem! I'll need to do a longer test later when I have time but the raster came up bright!  And it looks like the tube tester survived shipping with no issues. I tried the new 3AT2 (after looking up the proper settings in the manual) and it read full emission, and the old one got up to the ? between good and bad... So I think it was marginal and finally quit. Well, now that I have a tube tester, there's really only one thing to do: 
Last edited by MRX37; 10-24-2015 at 01:57 PM.
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#90
10-24-2015, 05:04 PM
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Looks like most of the tubes in that Motorola are in excellent shape! I do have a 6BL8 that came up on the lower end of the good range, but it's still good.
Decided to make a quick thank you video: http://www.youtube.com/watch?v=Z1Y6t...ature=youtu.be And thank you all for the assistance! Last edited by MRX37; 10-24-2015 at 05:08 PM.
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Yikes. There is no need to ground anything. If the fly is working OK, the screwdriver will draw a healthy 'air arc' a half-inch or so long. (Of course the screwdriver needs to have a well insulated handle to hold it by.) 
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