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Old cw?

Discussion in 'Ham Radio Discussions' started by KD2AFV, Jun 10, 2019.

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  1. WR2E

    WR2E Ham Member QRZ Page

    Four terminals?
    KA4DPO likes this.
  2. WF4W

    WF4W Premium Subscriber QRZ Page

    interesting... but not the fault of new hams for not knowing totally deprecated "technology" ...
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page


    Nice attempt at humor! It is a transformer mounted on the board. There are terminals on both sides of the device.

    On the underside of the board, there will be 2-terminals connected to the 2-each large pins on the tube socket. Those will be for the tube filament.

    Looking at the top: From the position of the tube socket in the photo, there is an arrow pointing to the outside of the socket. The small tube pin to the right of the arrow, as in the photograph with the volume control facing forward, is for the grid connection. The small tube pin to the left of the arrow is the plate connection.

    Here is a schematic that may be very close to what you have:


    Although 1.5 VDC is low for the type 30 tube filament, it will work fine. The type 30 vacuum tube is still cheap and I even have several NOS in their original boxes. I would use a B+ somewhat higher than the 4.5 VDC outlined in the schematic. At least 9 VDC and maybe even as much as 18 VDC.

    A "D" cell battery will provide enough current for the filament to operate for several hours and 9-volt transistor batteries can be used for the B+. The earphones need to be of the old like 2000-ohm type that were used for decades. Modern, hi-fi, phones are not going to work for several reasons.

    This circuit is very similar to a code practice oscillator that I built in Junior high school in like 1957. That oscillator used a type 30 tube.

    By the way, if you don't want the unit, I would be interested in obtaining it.

    Glen, K9STH
    NY7Q, VK2WP, AG5DB and 4 others like this.
  4. KB4MNG

    KB4MNG Ham Member QRZ Page

    I bet you can get $1,000,000 from it off ebay.
    VK2WP and K4AGO like this.
  5. KA8NCR

    KA8NCR Ham Member QRZ Page

    Lemme guess, you taught novice courses?
  6. W4NNF

    W4NNF XML Subscriber QRZ Page :)
  7. K4AGO

    K4AGO Ham Member QRZ Page

    It's an old Code Practice Oscillator. My guess is that it uses a type 30 tube. clean it up and use it or sell it on Bay. Some people (like me) love old equipment.
    W7UUU and W4NNF like this.
  8. VK2WP

    VK2WP XML Subscriber QRZ Page

    The old triode 30 was a versatile valve, years ago built a couple of regenerative recievers with the 30 and they worked well.

    Still have a two valve version which I have been threatening to get going one of these days.

    As a practice oscillator would explain the row of binding posts which would have been for battery connections.
  9. VK4HAT

    VK4HAT XML Subscriber QRZ Page

    No wonder i failed morse 3 times ;)
  10. W9BRD

    W9BRD Ham Member QRZ Page

    It's a code-practice oscillator. That's a rheostat for the tube filament.

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