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 Post subject: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 3:49 pm 
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Hi, I am in the market, looking at Type 47 tubes. As two out of three have turned out to be "duds", I was wondering what I should be on the lookout for in purchasing these tubes. Thanks!

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 3:57 pm 
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You need to find a reputable dealer who tests used tubes before selling them. EBay is probably not a good place to buy 47s.

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 3:59 pm 
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I know of one near me, but he only sells online- he doesn't have a storefront. For many, eBay is the only game in town.

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 4:03 pm 
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http://findatube.com/


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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 4:40 pm 
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Thank you! A

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 4:45 pm 
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His prices seem very reasonable.

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 6:10 pm 
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"Tested good" tubes on ebay is sometimes akin to "Ran when parked" buying a car on Craigslist.

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 9:30 pm 
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Probably not a problematic tube, just that in the sort of service they are used for, alot of the old used ones may be weak or bad, just like any other power output tube. "Tests good" on ebay may mean just into the green above the ? line and at that point, it might even still have some useful hours left in it, or not, depending on the circuit demands. Buying "Hickok tested" with some actual numbers might...might be safer.


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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Thu 06, 2018 11:12 pm 
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Avoid the globe or 247 "S" bulb version. There is always a chance the element distortion from a bump could cause a problem.

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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Fri 07, 2018 8:58 am 
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They weren't the best tubes. I remember reading about one engineer of the 1930s who called the 47 "ten percent (harmonic) distortion in a bottle."


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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Fri 07, 2018 1:22 pm 
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I had a Philco 70 that used them and I don't recall it being particularly bad for audible distortion but then it is AM broadcast.


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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Sun 09, 2018 10:51 am 
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Location: 253 Blanche St. Plymouth, MI USA
I dont find the #47's to be any worse than other tubes that were used in TRANSFORMER powered radios. When you get into the "series filament" radios, such as the "AA5 All American 5, the curtain burner cords, the ballast tube types, etc, then you have a higher rate of filament failure.

Tubes such as the types 25Z5, 43, 50L6, 50C5, and particularly the 35Z5 and 35W4 are known for higher failure due to the series filament situation they were put into.

Buying tubes online is VERY easy today from established tube sellers (I happen to be one). We all stand behind any tested tubes we sell. If you buy a "box lot" of untested tubes, expect about 15-20% to be bad ones for some reason, not necessarily open filament. More common is shorts or just poor emission.
At first I thought this thread was about the very common #47 BULBS, which have a very high failure rate due to being in the series filament radios as well.
Mark Oppat


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 Post subject: Re: Type 47 Tubes- what to look for
PostPosted: Dec Sun 09, 2018 11:54 am 
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ArthurTransOceanic wrote:
...... For many, eBay is the only game in town.

???
our megalist of resources lists MANY tube dealers that do not sell on EBay.....i would say that EBay is the last resort for tubes.

What to look for? How the tube checks out on a tube tester.

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