Discussion in 'Ham Radio Discussions' started by KD2AFV, Jun 10, 2019.
interesting... but not the fault of new hams for not knowing totally deprecated "technology" ...
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.
I bet you can get $1,000,000 from it off ebay.
Lemme guess, you taught novice courses?
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.
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.
No wonder i failed morse 3 times
It's a code-practice oscillator. That's a rheostat for the tube filament.