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#1
11-06-2008, 08:20 AM
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extremely poor focus
I've just found a 1968 "WEST" (italian-made) 20" B/W tube set on the curbside, it just needed a new heater ballast resistor and a 1B3GT HV rectifier, it works now, but it has a couple of issues...
First of all, the focus is really poor, and there are no adjustments for it, bad CRT? Then, the vertical deflection works fine but sometimes collapses to a bright horizontal line while changing VHF channels, is this normal? i'll post some pics ASAP! 
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#3
11-07-2008, 02:50 AM
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[QUOTE=Kiwick;2230060]Then, the vertical deflection works fine but sometimes collapses to a bright horizontal line while changing VHF channels, is this normal?[QUOTE]
No, this is not normal. More than likely there is a bad connection that is breaking with the vibration caused by the ratcheting action of the tuner. Cleaning the sockets and pins of the vertical output and vertical oscillator tubes may knock it out. If not you can take an INSULATED tool and gently tap the tubes while the set is playing. EVEN WITH AN INSULATED TOOL WATCH WHERE YOU PUT YOUR HANDS IN A LIVE SET!! A tube with an internal short of some sort will react to the tapping in the same way as the reaction caused by changing channels, only now you more than likely have isolated the problem with the individual tapping. Beyond this there is always the possiblilty of a bad solder joint or even a broken or dirty potentiometer. The faulty tube or dirty pins/socket is the most likely cause IMHO..... I hope this helps... 
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#4
11-07-2008, 01:26 PM
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Definitely not a problem with bad connections as the vertical also collapses when i unplug the antenna lead from the wall socket, it does this for about a second or so then it comes back with a stretched raster that returns to normal dimensions within a couple of seconds.
The focus and contrast has improved a lot with use! now it's almost perfect!
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#5
11-07-2008, 02:34 PM
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The erratic vertical sweep could perhaps be traced to sync stages, if changes in signal seem to cause the problem. Check associated tubes. Check that B+ handling resistors haven't drifted in value. Check blocking caps in the sync circuitry to be sure you don't have a leaker.
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| Audiokarma |
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#6
11-08-2008, 02:57 AM
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Quote:
 I'm sure that there would be a lot more collapsing than vertical sweep if the antenna were plugged into a 110 v.a.c. wall socket. But seriously, the focus and contrast improving with use is no surprise at all. I have found that if you luck out and get an old radio or television to play for more than a few minutes after decades of dormancy, the more you let them play the more bugs work themselves out. I'm fairly certain that this is due to the old capacitors sort of re-forming (rejuvenating) themselves which takes a bit of time. I have only read a small amount on the subject of whether or not capacitors can even be "re-formed". There is a process to this in which I am sure that there are already threads on, and it goes way beyond simply plugging a set in. It seems to always be debatable whether or not old caps can be used, or more so trusted. As an owner of two TV sets, and quite a few radios over 50 yrs. old with all original (or mostly) caps I can say at least that they CAN last a VERY long time. Most particularly electrolytics....
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free"
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#7
11-08-2008, 04:43 PM
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Of course, the "wall socket" is a coaxial aerial (OTA) socket...
after playing the set for almost 24 hours uninterrupted, the focus is now perfect and the picture is really bright and crisp! it's a cheap, basic set, but despite the smallish speaker, the sound is quite good with an amazingly deep bass response!
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#8
11-09-2008, 12:56 AM
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Very nice! Until I saw the pics I had forgotten that we were talking European. I was just thinking how Euro sets must have long had that certain look about them that always, to me, says European. I guess its the lack of c.r.t border. When I was stationed in Germany during the 1980's I was given a Grundig (I think) set that I could only play German channels on. It was not very old then but looked very similar to this set. Again the sets over there definitly have a distinct look......
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#9
11-11-2008, 08:23 AM
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I've noticed that there's some melted wax in the bottom of the HV cage under the flyback, is that a sign that the fly is about to go?
anyway, we also had American-looking sets here in the 60s... like these Italian Phonola sets i have:
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#10
11-11-2008, 09:48 AM
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Quote:
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| Audiokarma |
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#11
11-11-2008, 11:19 AM
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On radios and TV's improving with use: also, the tube heat drives moisture out of coils, IF transformers, etc. thus adding to the improvement.
Reece
__________________
Reece Perfection is hard to reach with a screwdriver.
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