The Vacuum Tube, A Look Back

Update at Bottom.

I know this is off topic for our blog, but one of my hobbies is messing with old radios. These are vacuum tube sets from the 1920’s and 30’s.
I’ve written several posts about one of my “unidentified” radios over the years (see here and here). Recently, Andrew was able to shed some light on the original tubes this radio would have used, the UV-201 Triode.
After I read his emails, I remembered that I had one of these tubes. I liked it so much that I mounted it for display.
I know, I know…you all are saying “how cheesy is that”! Well, can’t say I blame you, but hey, we all have our quirks.
Here’s my tube:



Here is the data sheet for the UV-201 vacuum tube from one of my books. This particular book is copyright 1920. I included some data sheets that I found on the internet too.
UV-201 Data Sheet

Update 5/52009:

Here is an excellent article on the history of the UV-201 tubes.

3 Responses to “The Vacuum Tube, A Look Back”

  1. Steve says:

    I don’t think this particular tube is any good. The grid shield surface is in pretty bad shape and there is a lot of oxidation on the plate.
    I don’t know if they used getter back then to show the tube integrity, but my best guess is that this one has lost its vacuum.
    Makes for a nice display piece though.

  2. Russel Foran says:

    Thanx so much for posting this info on the Type 201A tube.
    Ever heard of a tube manufacturer named: GEM?

    I bought this old “farm radio” (circa 1920’s), which was designed to run
    on batteries. It has two “Type 201A” tubes, made by GEM, whoever
    they were. They appear to be the same as the types you describe
    here. I’ve spent quite a bit of time learning about the old technology
    from this time period, and have scavenged a couple of DC power
    supplies to run this old radio. The tech details on this tube (especially the
    filament voltage and the plate voltage) were what I needed to ensure
    I was running within limits, so as not to destroy the old tubes.

    The radio works, (as well as any regenerative-type receiver can be
    expected to..!), and it is a treat to listen to at night with sensitive
    high-impedence head-phones. “Seemed about a hundred years ago..”
    Thx again..
    – Rus

  3. Steve says:

    Hi Rus,
    All UV-201 are 5 volt tubes. If you can, I would start with a filament voltage of 2.5 to 3 volts and increase it slowly up until the radio is giving you decent performance. Be sure not to exceed 5 volts though. Also, make sure none of them are “running away” with excessive plate current. You can do this by watching the current draw on the plate voltages.
    As for the GEM company, I believe that RCA made many tubes that were “brand labeled” for whatever company was going to sell them. Most likely your tubes are RCA.
    What model of farm radio do you have?

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