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 Post subject: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 12:07 am 
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Joined: Mar Fri 27, 2009 8:57 pm
Posts: 485
Location: Alexandria Louisiana
I am restoring a RCA 7T1 tombstone, and using the following tubes, 6A8G,6K7G,6H6G,6F5G,6F6G, and 6U5/6G5 tuning eye tube, what sub would be best to use for the 5W4G. That tube is not easy to come by NOS. Thanks, Carl-Louisiana


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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 1:42 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12582
A 5Y3 is probably best sub...

The 5W4 has a 1.5A filament vs 2A of 5Y3, but I can't think of a similar rectifier with 1.5A...

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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 3:24 am 
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Location: Aurora, CO
Looking at the schematic, it appears the OEM tubes were metal, not glass "G" types.

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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 3:32 am 
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Location: Livermore, CA
Here is the schematic:

http://www.nostalgiaair.org/pagesbymode ... 015143.pdf

It really doesn't matter if this rectifier is glass or metal. If a person wants to stay with metal another sub might be 5Z4. Elements are closer spaced so B+ will be a little higher but it won't have the instantious over high voltage of a 5W4 or 5Y3.

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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 5:35 am 
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Location: Detroit, MI USA
Agree that a 5Y3 is the closest sub you can find for the 5W4 electrically. The extra 1/2 amp of filament current should not be a problem.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 7:05 am 
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Joined: Apr Tue 19, 2011 6:24 am
Posts: 369
Location: 07470
Consider the metal 5T4, if you have room for it. It is a very useful tube, but it's the same size as a metal 6L6.

The 5T4's coated filament draws 2 Amps, and its internal voltage drop (B+) is a bit closer to the 5W4's than those of the cathode-type 5V4 and friends. Warmup time is quicker than the 5V4, 5AR4 types and this should be considered.

Get a tube manual and look at the plate regulation curves for the kind of filter your set uses (~ likely capacitor input) and compare these tubes. The 5T4 is much sturdier than a 5Y3x, but harder to find. However, if you need a metal tube, and can't find a 5W4, maybe this can work for you.

Here's a nice ARF thread from 2011 on various other rectifier tube substitutions http://www.antiqueradios.com/forums/viewtopic.php?t=42506 .


73,
OTH


Last edited by OTH on Mar Thu 01, 2018 8:07 pm, edited 1 time in total.

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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Thu 01, 2018 6:34 pm 
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Joined: May Wed 16, 2012 6:58 pm
Posts: 267
Location: Eastlake, Michigan
Bob Dobush, http://www.findatube.com/ , has new 5W4 for $5.00, used $2.50.


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 Post subject: Re: Best sub for 5W4G tube?
PostPosted: Mar Sat 03, 2018 8:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5122
Location: 253 Blanche St. Plymouth, MI USA
Carl, I have that tube and when I send the switch we've been talking about I could send one.
Mark Oppat


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