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 Post subject: Why would a ballast tube be needed in this circuit?
PostPosted: Jan Fri 07, 2011 5:16 am 
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Would someone take a moment to look at this schematic of a Packard Bell model 48 http://www.nostalgiaair.org/PagesByModel/886/M0012886.pdf
and explain to me why a ballast tube would be used this way on the primary side of a power transformer. If the power transformer would be rated at 120vac on the primary, what useful purpose would this serve.
Also, in this circuit a CL 610-10 ballast is used. I can't find any data on this tube. Can someone point me in the right direction. Thanks......Dave


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PostPosted: Jan Fri 07, 2011 5:52 am 
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The transformer probably was not rated for 120 VAC. Other sets used similar configurations. The Majestic 90 used a ballast on the primary. I think the primary was rated for 90 volts in that radio. It was an attempt to provide better AC line voltage regulation for those early sets.

Pete


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PostPosted: Jan Fri 07, 2011 2:58 pm 
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There are several types of ballasts. Some are simply used for dropping voltage in a series filament string. Other types are used for voltage regulation (like those used in Zenith T/O's). This one appears to be intended for voltage regulation of the input to the transformer primary to compensate for different or varying AC mains voltages.

Here is an article about ballast tubes which I copied from an old radio magazine (can't remember which one).

http://antiqueradios.com/gallery/d/1320 ... 1159855fd3

Dave


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PostPosted: Jan Fri 07, 2011 5:42 pm 
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Dave Doughty wrote:

Here is an article about ballast tubes which I copied from an old radio magazine (can't remember which one).

http://antiqueradios.com/gallery/d/1320 ... 1159855fd3

Dave


Thank you...this is a great article..


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PostPosted: Jan Sun 23, 2011 2:01 am 
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Long ago I had an old Bremer-Tully radio that used a regulating ballast ahead of the power transformer. Somewhere I found a description of it. The filament was made of iron and it was enclosed in a hydrogen-filled, frosted glass bulb. Looked like a light bulb except for the two-prong bakelite base.

Apparently the resistance of iron wire changes dramatically with temperature, so it made a good voltage regulator. It also made a not-so-good dim bulb tester of sorts when I shorted something out on the chassis and blew it! :(

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

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PostPosted: Jan Mon 24, 2011 12:38 am 
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Dave Doughty wrote:
Here is an article about ballast tubes which I copied from an old radio magazine (can't remember which one).

Dave


Thanks Dave, I have been learning a little about these ballasts, having this un-branded 4-tube I'm trying to understand. (it doesn't appear to ever have had a ballast, but similar circuits I'm running across do). The article is very good.

I take it then that resistance line cord sets usually, but not always, do not have a ballast.

- divad


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