HOW DOES THE 3W1 WALLBOX WORK?

ok, to get both machines connected I had first to understand how the wallbox works. As I said before, the 3W1 handles the communication with the Jukebox trough 3 wires. Two are for power supply and they can be connected to the 24 AC from the Sinfonola, the other is the clever guy, the one sending the selection keyed in the wallbox, that has been previously encoded in pulses.

 WALBOX PULSING

Everywhere in the manuals (and I will do the same), it is said that the walbox is “sending pulses” to the stepper unit to indicate the selected combination of a number + letter.

We say “sending pulses”, because is a more graphical figure, but it is not true: The poor walbox does not send anything, simply switches to ground or not the wire for signaling.

Once said this is very important that if we do any design using the signaling circuit, we do not pass current trough it. Originally the signaling was connected in the Jukebox to a vacuum tube that draws no current from the circuit. If instead we install a relay that will take some milliamperes, we will have sparks that will wear out the contacts in the wallbox. If you do your own design, try to use a transistor: in our case we will use an optocupler to isolate the voltages in the wallbox to the rest of the circuit.

HOW THE PULSES WORK:

The wallbox has a disk with a central blade that when rotating wipes trough 26 contacts. Depending on how the selection keys ground these contacts, we will have a different number of pulses:

- The wallbox first sends a train of pulses, one per number selected (i.e. if the selection is A-8 it will send 8 pulses).

- Immediately after it will send 11 pulses if the selected letter was even (B, D, F, H, K) or one single pulse with a width of 11 if it was and odd letter (A, C, E, G, J).

- After this will send nothing for 2 pulses width time.

- It will then send 1 pulse if the letter was A or B, 2 for C or D, 3 for E or F, 4 for G or H and 5 if it was J or K.

SOME EXAMPLES

Just to be able to visualize this, which is no easy, I made the followin drawing:

The first train of pulses is the most complex one: 10 – K, so has 10 pulses for the number, 11 pulses for the even letter, a pause of two and 5 pulses for the K.

Next is the easiest: 1 – A which is 1 pulse, the large pulse for odd letter and 1 for A. Only three pulses in total, this is the shortest possible.  The next is 1 – B, the difference here is 11 more pulses for the even letter.

Try to figure out the last one!

In the next entry (now that is clear to me how the wallbox operates) I will go for the Sinfonola200, which is a bit more complex.