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 Post subject: 201A tubes for Battery Radios Tip
PostPosted: Jun Wed 24, 2020 4:39 am 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
For new entry into 1920s battery radios.
Battery radios in the RF section need the highest GM measurement 201A tubes to be found. My radio hears nothing with a 600 gm used 201A. Even an 800 gm is not great. Every 50 gm increase improves the reception. I use a 1000 gm in first RF position and 950 gm in second RF position. I believe minimum new spec for a 201A is 850 gm. So, it is about useless to buy a used 201A for your 1920s battery radio in the RF sections. 600 gm as an audio driver works fairly well.

Now, a 201AA or 01AA tube has an oxide filament. At reduced filament voltages as supplied by the radio rheostat (volume control) the oxide filament has much higher emissions at reduced filament voltage vs the standard 201A tungsten filament. The 201AA or 01AA really wakes up the radio. This is the tube I use in the first RF section and second RF sections. They usually measure 1000gm and a rare double upside down 'W' filament measured 1400gm. Most are an upside down 'V' filament..

Note- used 201A tubes on ebay have most for sale not even tested. On tubes tested very few list the gm so you still do not know what is being offered. Careful about ebay NOS tubes. Some tube manufactures do not match the box- dead giveaway that is a used tube. Buying new 201A tubes here at AR is your best bet.

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Last edited by jimbenedict on Jul Thu 23, 2020 1:04 pm, edited 2 times in total.

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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Jun Wed 24, 2020 5:33 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16897
Location: S. Dartmouth MA 02748-1225 USA
:wink:

Fair warning, 20's era radios were designed for average tubes. Using "hot" selected tubes could result in uncontrolled oscillation from excessive gain in stages and microphonics. Reflex receivers and those built without any stage shielding would be most vulnerable...
Most often bad performance can be traced to poor connections, moisture in RF coils, lack of correct neutralization, low primary "A"voltage.

RCA recommend exchanging tubes in sockets for best performance

YMMV

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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Jun Wed 24, 2020 4:20 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
Chas wrote:
:wink:

Fair warning, 20's era radios were designed for average tubes. Using "hot" selected tubes could result in uncontrolled oscillation from excessive gain in stages and microphonics. Reflex receivers and those built without any stage shielding would be most vulnerable...
Most often bad performance can be traced to poor connections, moisture in RF coils, lack of correct neutralization, low primary "A"voltage.

RCA recommend exchanging tubes in sockets for best performance

YMMV

I would restate your reply 'some' 1920s radios. Neutraldyne type radios would likely not have issues. My experience is using a Arborphone model 27. A 650gm 201A in RF section only receives a few stations at maximum volume, a 1000gm 201A has about 25 stations received at night at 1/2 volume. Here is a quote from another member:
atwaterkent1 wrote:
For 20's battery radios tubes need to be more than just good, they need to test in the high range to get the best performance from them. As you found out, it can make quite a difference.

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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Jun Wed 24, 2020 5:00 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16897
Location: S. Dartmouth MA 02748-1225 USA
I am so now well informed about battery radios... :lol:

Have you ever successfully flashed a 201a?

YMMV

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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Jun Wed 24, 2020 5:53 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
Chas wrote:
I am so now well informed about battery radios... :lol:

Have you ever successfully flashed a 201a?

YMMV

No, all my 201A tubes are NOS. I would not use or buy a used 201A or 201AA tube.

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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Dec Sat 12, 2020 2:53 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1239
Location: St. Louis, MO, USA
I have rejuvenated about 1in10 201As. Resoldering the pins due to corroded solder fixes another 10% in my experience. Another tip, already mentioned in other responses is to hook up the tube filament circuits first. If you make a miswiring mistake the tubes either light or don’t light but aren't Burnt out. If you miswire the B+ by mistake and get that voltage across the filaments you might burn out every tube in the radio.

Dennis


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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Dec Thu 24, 2020 6:21 pm 
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Joined: Aug Mon 18, 2008 3:17 pm
Posts: 1192
Location: Dallas Tx.
I've never had a problem with average 01A tubes. Swapping tubes around for best reception usually works good. The weak or weakest tubes usually work best as detector tubes.
Normal tubes work best in regen sets. High gain 01A's do not work well.
If you need high gain tubes you are in a poor reception area or have antenna and ground problems.


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 Post subject: Re: 201A tubes for Battery Radios Tip
PostPosted: Dec Sat 26, 2020 6:02 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
homebrew wrote:
I've never had a problem with average 01A tubes. Swapping tubes around for best reception usually works good. The weak or weakest tubes usually work best as detector tubes.
Normal tubes work best in regen sets. High gain 01A's do not work well.
If you need high gain tubes you are in a poor reception area or have antenna and ground problems.

As Chas mentioned including myself high gain 201A tubes are better. Nothing is wrong with my radio and I use a 130 foot antenna. Radio receives on 30 foot antenna, but much stronger signals on the 130 foot antenna.

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