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 Post subject: Weird chassis
PostPosted: Jun Mon 26, 2017 2:29 pm 
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Silvertone 6201. This set uses a 25Z6 rectifier. It also has a transformer. Most tube filaments are run in series off the transformer secondary, except one with a separate winding, which also lights the lamps. How weird is this?

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 Post subject: Re: Weird chassis
PostPosted: Jun Mon 26, 2017 2:32 pm 
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Unusual for sure, I have seen a few other sets that were designed the same way. Who knows what the engineers were thinking? They may have been told they had to use a transformer, but also had a good stock of certain tubes they needed to use up.

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 Post subject: Re: Weird chassis
PostPosted: Jun Mon 26, 2017 2:52 pm 
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So, this is essentially a AA5 radio that is not a "hot chassis" set thanks to the use of a line power transformer. Beyond that, there doesn't appear to be any particular advantage to this design... which is possibly why it hit an evolutionary dead end.


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 Post subject: Re: Weird chassis
PostPosted: Jun Mon 26, 2017 3:41 pm 
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Guess the AF preamp 6F5 is run off a separate winding nearer earth for hum reasons.

Gary


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 Post subject: Re: Weird chassis
PostPosted: Jun Mon 26, 2017 4:40 pm 
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The transformer eliminates the series resistor usually needed with that tube string.
The docs list 11 models with that chassis.

I wonder if the tuning eye tube was added as an afterthought? Luckily there was a 6 volt tap available for one of the 6 volt tubes.

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 Post subject: Re: Weird chassis
PostPosted: Jun Tue 27, 2017 3:29 am 
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I've seen some very interesting sets over the years that used the 25L6, 25Z6, and perhaps another 25 volt fat pinned tube that I can't think of right now.

I really never liked their performance either, but that may have been just a coincidence.

I do remember that they physically ran so very hot.

steve

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 Post subject: Re: Weird chassis
PostPosted: Jun Tue 27, 2017 5:34 am 
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Dutch Rabbit wrote:
I've seen some very interesting sets over the years that used the 25L6, 25Z6, and perhaps another 25 volt fat pinned tube that I can't think of right now.

I do remember that they physically ran so very hot.

steve
Maybe a 25A6 power tube? They run hot at 0.3 amps, double what you see in the standard AA5 string.

One weird version is that 1949 Philharmonic Minuet. In place of a ballast tube or candohm resistor, they used two 25Z6 rectifiers with the two 25L6's. Those were cheap tubes by that time, I imagine.

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 Post subject: Re: Weird chassis
PostPosted: Jun Tue 27, 2017 11:25 am 
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Technically a 25L6 or 25A6 shouldn't be any hotter than a 50L6.

All their heaters run at 7.5 watts, unless I'm missing something....

-Steve

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 Post subject: Re: Weird chassis
PostPosted: Jun Tue 27, 2017 3:50 pm 
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You are correct of course, Steve. It would be the resistor, not the tubes, that warms up the chassis.

Attachment:
resistor.jpg
resistor.jpg [ 166.54 KiB | Viewed 1492 times ]


The Silvertone with a power transformer would be an improvement in that regard, but probably had to be priced higher than the AA5's of the competitors. Anyway it is an interesting piece of radio history.

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 Post subject: Re: Weird chassis
PostPosted: Jun Tue 27, 2017 8:59 pm 
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yes, it was the 25A6 tube of which i could not remember.

i had a couple table radios that had 25 volt tubes in them with some 6 and or 12 volt tubes inside, perhaps a ballast as well. they were made up of octals and tubes with the pins of various thickness.

the few radios that i had with 25 volt tubes et al. inside were little space heaters. the cabinets would become very hot to the touch, much hotter than any bakelite AA5/6 that i ever had.

i did not like those radios for many reasons, heat being one of them.

i sold them off when i was downsizing years ago.

one was a little "kent" wooden set with suitcase type covering on it. i can't imagine how it never physically burned itself up.

steve

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 Post subject: Re: Weird chassis
PostPosted: Jul Sat 01, 2017 2:18 am 
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Dutch Rabbit wrote:
yes, it was the 25A6 tube of which i could not remember.

i had a couple table radios that had 25 volt tubes in them with some 6 and or 12 volt tubes inside, perhaps a ballast as well. they were made up of octals and tubes with the pins of various thickness.

the few radios that i had with 25 volt tubes et al. inside were little space heaters, and when it comes to these things that relate to these you can be sure that they look into it. There are certain categories there. The cabinets would become very hot to the touch, much hotter than any bakelite AA5/6 that i ever had.

i did not like those radios for many reasons, heat being one of them.

i sold them off when i was downsizing years ago.

one was a little "kent" wooden set with suitcase type covering on it. i can't imagine how it never physically burned itself up.

steve


I think my grandfather had that "kent" one you're talking about, if I remember correctly there was a burning incident associated with it but I don't know all the details. Do you have a picture? I am not sure if we're talking about the same thing.


Last edited by mayni on Sep Tue 26, 2017 1:29 am, edited 1 time in total.

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 Post subject: Re: Weird chassis
PostPosted: Jul Sun 02, 2017 5:22 pm 
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nope, i thought i had a pic, but that radio is long gone for many a reason.

one could have made breakfast on it if the top were teflon :shock: .

steve

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