Last week we explored the record changing
mechanism in this…
charmingly ugly,
stylistically repressed
clunky buzzy disc jockeying gizmo
box of horrors.
We looked at the mechanical bits that grab
the record, manipulate the tone arm and turntable,
and all that jazz.
We also created a circuit with a relay to
start and stop an action with two separate inputs.
Also known as buttons.
Yeah, I’m gonna try to explain that a little
better in this video, but
anyway if you haven’t seen the video that I’m talking about right now,
you should probably consider watching that first.
In fact,
here’s a card!
I’m just kidding,
there you go.
And for all those situations where cards don’t
work, there’s a link in the description.
Of course this is upside-down, but we’re
gonna roll with it.
I left you with a devastating cliffhanger.
You see, we covered how this machine is able
to take a record from the record carousel
and play it, but we never covered how exactly
it knows what record to play.
Well, that’s what we’re gonna cover in
this here video.
Shocking, I know.
So let’s consider what needs to be accomplished.
We don’t have the luxury of a computer;
we only have a few relays and whatever sort of mechanical contraptions we might devise.
How could you design a sort of memory to store
a selection to be played given those limitations?
Why with a ridiculously complicated electromechanical
solution, of course!
And....
THIS is it!
Exciting, huh?
This is the Selection Accumulator.
This device functions as the memory of the
jukebox.
Calling it memory is a bit of a stretch, as you’ll soon see, but it does store selections to be played.
Just, in physical space.
Using physical objects.
You’ll notice that all around the edge of
this are a bunch of little metal pins.
They each have a spring attached to them,
well most of them anyway,
and they’re labeled just like the selections of the jukebox.
See, each of these pins is a selection.
There are 200 in total, starting at A1 and
ending with V0.
By the way, if you noticed that the letters
I and O were missing, that was done just to
prevent confusion between those two letters
and 1 and 0.
Take a closer look at the springs and you’ll
see that they’re all under tension.
Right now, these pins are just barely staying
held down.
They’re really on the edge of their seats.
If you push one ever so slightly towards the
center of the…
let’s call it a basket,
it will suddenly pop up.
[click]
That sounds like a click I’ve heard before!
Anyway, thanks to the spring it will stay
in the popped up position until something
pushes it back down, and then it will be caught
on the edge again so it stays down.
So, let’s say you had selected C5.
Well, in that case, the pin for C5 will be
popped up.
And then the jukebox knows to play C5.
If you have questions regarding how the pin managed to become in the popped up state,
or how that translates into the jukebox actually playing C5,
stay tuned because I’m about to answer them.
But first, buttons!
And I do mean buttons.
The selection buttons up here on the top of
the jukebox are what makes those pins pop up.
It’s really fascinating.
So, firstly, recall from the last video that
when you push in these buttons,
they stay held in until the selection accumulator has
done its thing.
This serves two functions:
One, it’s how the jukebox keeps you from
making selections unless you’ve put some money in it,
and two it creates a circuit
across the letter and number patches.
Hold that thought, we’ll get back to it.
Way up here is the Latch Solenoid.
This must be energized in order for a selection
to be made.
If it’s not, as is the case when the jukebox is turned off, you’ll see that the buttons do not stay down.
Unless the jukebox’s Credit Accumulator,
which unfortunately does not work on this machine,
registers a credit, this solenoid
will not be energized and you cannot make a selection.
And before you think of getting all crafty
and just holding them in for a bit,
the latch solenoid also moves these various leaf switches, setting up other circuits that come into play.
So you cannot possibly make a selection unless
this solenoid is powered.
The latch solenoid is held in by Relay 1,
one of four relays in this junction box.
The junction box is mostly just a box that
a lot of things plug into.
Basically it’s just a bunch of wires in here
going from socket to socket,
but these four relays handle some of the various shenanigans we’re about to see.
Anyway, relay 1 receives power from the
credit accumulator.
This is the device that counts your money.
Here’s a brief look at the credit accumulator.
Again, it doesn’t work, I’ve not been
able to make it work,
but what it’s supposed to do is add and remove credits from the machine
based upon which selections you make and which coins you insert.
Were it working it’s surprisingly versatile,
allowing you to set the number of credits
each coin gives you, and even do things such
as require two nickels for one credit.
It’s wired to the coin mechanism down here,
an equally fascinating bit of tech,
which validates and sorts nickels, dimes, quarters,
and even half dollars,
all done by gravity alone.
Missing from the machine at the moment is
a blue plastic coin chute which would direct
coins from the slot up above down to the top
of the coin mech.
Anyway, depending on the coin it would fall
onto one of these four switches, and that
would - or should anyway - make the credit
accumulator count up however many credits
you set it to with these levers and junk.
Anyway, again;
it doesn’t work, which is a bummer,
but thankfully someone has rigged this machine
to simply always behave as though it has a
credit.
So, relay one is energized, and therefore
so is the latch solenoid, whenever it’s powered on.
OK.
So, back to the buttons.
With the latch solenoid held in, press one
letter and the button will stay depressed.
You can see the latch mechanism through this
hole in the top of the jukebox that definitely
shouldn’t be there but it is anyway.
By the way - don’t think of any funny
business and try to select two letters or two numbers
at the same time.
Wurlitzer’s way ahead of you -
the lower one will get priority.
Anyway, press a letter, then a number.
So again, C5.
A lot is about to occur in the next two seconds.
Strap in.
Once both a letter and a number are selected,
these leaf switches will energize Relay 2,
which is one of the relays here on the junction box.
Interestingly, the junction box has different
names for these four relays,
despite the fact that the service documentation only refers to them by numbers.
Anyway, the closing of relay 2 completes the
circuit to the selection accumulator motor.
That’s this guy!
You may have noticed this weird thing sitting
in the middle of the basket.
Well, when you make a selection, this goes
for a spin.
A 180 degree spin, in fact.
And you know what makes that happen?
Why, Relay 3!
Heyo, it’s time for that button demonstration
to come back into the fold.
But this time - it’s not a button.
It’s a circuit board.
Notice what happens when I give the little
spinny thing a push.
It suddenly starts moving, then stops again.
How’s that happening?
Well, notice these contact patches.
You’ll see that there’s a break in them
on both sides.
Well, this one’s not really a break but hey, let’s not get pedantic.
That’s my job.
On the bottom of this arm are four wiper contacts.
These two here provide power to relay 3.
Now, at rest, the circuit is broken.
So, relay 3 is de-energized, and the motor
doesn’t get any power.
But, if I push this far enough to where the
wipers touch the patches, relay 3 will close
a switch contact inside itself, powering the
selection accumulator motor.
The motor will stay powered through a 180
degree sweep, so it will keep spinning,
but once the contacts make it off the patch, the
relay opens the switch, and the movement stops.
Now, you saw that I needed to give this a
push to start it going.
But after that point it completed its task
on its own.
Relay 2 is what gives it that initial push.
That happens as soon as both a letter and
a number button are pressed in.
Once it’s moved from its starting position,
relay 3 takes over.
And once it’s made it to the end of the
rotation, relay 3 is released, and the motion stops.
Oh and by the way, all these other contact
patches did various things,
including removing a credit from the credit accumulator
(if it were working)
and releasing relays 1 and 2.
OK, now we are not getting deep into the specifics
here.
This is how relays 1, 2, and 3 are represented
in the schematic.
It’s nuts.
This is very difficult to follow,
especially since you have to go from one page to the next to make sense of anything,
so for my descriptions of what’s going
on here
I’ve been relying on the much more helpful Sequence of Operations section
of this lovely service manual.
Now, in regards to the red and green button
demonstration from before…
well first let me acknowledge how unsatisfied with that explanation I am.
I really should have been more specific about
what the buttons were accomplishing in the circuit,
and a schematic would probably have
been helpful at least to some of you.
So, this time, no buttons.
Ah crap, but this all gets started ‘cause
of the selection buttons!
Ugh.
Well...
Basically, and I’m not promising or even
trying to achieve perfect accuracy here, when
both a letter and a number button are held
in, these weird linkages cause one of these
here switches to energize relay 2.
Inside relay 2, a pair of switch contacts closes
which provides power to the
selection accumulator motor.
So it starts spinning.
Once it’s moved out of its park position,
this track here energizes relay 3.
Relay 3 also has a pair of contacts inside of it that provide power to the selection accumulator motor.
Now, relay 2 can be released without stopping
the motor.
So, relay 2 got this going, but once it left
its park position,
it could keep going on its own because of relay 3.
Now, I’d love to get into more of the specifics
regarding these patches, but...
unfortunately I can’t make any sense of how they relate to the other things that are going on.
For example, remember relay 1?
Well, that guy is supposedly powering the
latch solenoid, based upon whether or not
there’s a credit in the credit accumulator.
But power to the latch solenoid has to be
released briefly when the selection accumulator stops
in order for the selection buttons to
pop back out,
and I can’t say exactly what causes that.
Does relay 1 momentarily get de-energized
thanks to one of these patches?
Or is the solenoid itself powered through
here?
I don’t know, and I’ve been staring at
these schematics for hours, and my brain hurts.
All I’d like you to see here is how we can
make a bunch of things happen in sequence
by running some contacts over some patches.
This is yet another kind of program;
I hesitate to say this but it’s a lot like a series of buttons that are getting pressed automatically in sequence.
Yes, these aren’t buttons, but they’re
sets of contacts getting bridged as the wiper
runs past them, one after the other.
So, it can cause various actions to occur
at various times,
depending on how and to what these contact patches are wired.
This is what electromechanics are, people.
It’s a buncha wires, all going to different
places, and all through different things.
And now to the most important thing of all.
The pins.
So, this spinny thing is officially called
the Shaft and Magnet Assembly,
and on both ends you’ll find a Selector Magnet.
This is an electromagnet which travels just
behind each of the pins.
You’ll notice that down here are a pair
of wiper contacts, and they are travelling
over all of these teeny tiny patches.
This is where the real magic happens.
Each of these thick bars on the inner edge
is wired to one of the letter buttons.
So we’ve got A over here, B is next to it,
and so on all the way through V.
These teeny tiny patches along the edge are wired to numbers 1 through 0,
and they repeat over and over again.
Looking on the bottom you can see how there
are wire links connecting every tenth patch together.
When two buttons are pressed, there’s power
across one of these letter patches,
and twenty of the number patches.
See where this is going?
When you’ve selected C5, the C patch and
all of the 5 patches become a power source
for the electromagnet.
I’m not sure which one is live and which
is neutral, and in fact this is an AC circuit
so it doesn’t really matter anyway, so let’s
just say there’s voltage across the two of them.
As the magnet arm sweeps, the electromagnet
is just chillin' doing nothin'.
Sure, there’s voltage on all of these 5
patches, but there’s nowhere for that voltage to go.
Except at C5.
Right when the electromagnet is behind the
pin for C5, it gets a brief pulse of power,
pulling the pin towards it, which causes it
to pop up with the help of the spring.
Isn’t that just the coolest thing?
With one letter and one number, there’s
only one spot on this entire board where a
circuit is actually complete between the inner
and outer rings.
The reason there’s an electromagnet on each end of the arm is that it only rotates 180 degrees per cycle.
Now, the very last thing this mechanism
is responsible for
is providing a pulse of power to the Override Magnet.
That’s this guy.
The override magnet pulls on a little latching
mechanism to close this leaf switch.
This switch is essentially the master power
switch for the entire record changer.
So long as it’s closed, the carousel, Wurlamatic,
and all their associated doodads now receive power,
so it can start looking for the record
to be played.
And how does it do that?
Why, with the Readout Arm, of course!
This is what I said connects to the black
bar underneath the record carousel in the last video.
The readout arm is what actually translates
the popped up pin into a record to be played.
You can see it has these little feeler levers
connected to two switches.
When the selection accumulator is installed
in the jukebox, it hangs directly underneath
the record carousel, and the feelers of the
readout arm travel right above the pins as
the carousel rotates with the motivation provided by this motor
You may have noticed already that every other
pin is shaped differently.
All of the odd selection number pins have
a notch in the side facing the outside edge,
and the even number selections are the opposite.
That’s so the correct feeler is activated
depending on whether the selection is the
A side or the B side of a record.
See, these two pins are both the same record
in the carousel.
That’s why readout number 2 is resting farther
forward than 1 - they need to stop the carousel
in the same place, but the pin for side 2
is farther ahead in the rotation.
Side-note;
It annoys me greatly that Wurlitzer refers
to everything as Side 1 and Side 2 when it
has long been established that 45’s have
an A side and a B side.
In case you haven’t been doing so this whole time,
please note that Side 1 corresponds to Side A, 
and 2 corresponds to B.
I don’t really know if Wurlitzer was trying to alleviate
confusion with selections A and B, or if they
had some other reason for not calling these
Readouts A and B, but here we are.
Anyway…
These two readout switches are connected to
this contact board up top via these feelers.
Fun fact!
These are my biggest source of problems with
this machine.
You’ll notice that a few of them are all bent out
of shape,
and only some of that was my doing.
These contacts need constant cleaning in order
for the jukebox to work correctly, as the
timing of when these feelers hit the pins
and thus stop the carousel
needs to be fairly precise.
Now, you may recall from the last video that
the side one and side two relays were what
started the Wurlamatic mechanism and thus
pulled a record out of the carousel to be played.
Well, these are what they’re wired to.
If readout 1 gets tripped by a selection pin,
that energizes the side 1 relay,
which stops the carousel,
activates the Wurlamatic,
and also energizes the side 1 solenoid so that
the record takeout arm’s left pin gets caught
by this catch, and it pivots into position
to play side one of the selected record.
The same thing happens when the side 2 relay
is energized by readout 2, although the side
2 relay does not energize the side 1 solenoid,
therefore causing the take-out arm to pivot
in the opposite direction.
So then, here’s a question a few of you
have probably been asking by now;
How does the pin go back down?
Aha!
Well, that’s not the job of the selection
accumulator.
It has no ability to reset the pins.
But, the readout arm does!
There are a pair of small solenoids on top
that are attached to these little metal pusher things.
Thanks to a switch buried deep within the
Wurlamatic mechanism, called the cancel switch,
these solenoids briefly get power during the
course of its rotation and push the pins back down.
One of the key components that I haven’t
mentioned yet is the Magazine Lock Solenoid.
That loud buzzing it makes as the carousel
turns is coming from this.
It probably shouldn’t be that loud, but
the machine is 50 years old, cut it some slack.
The reason it’s important is that it aligns
the carousel whenever it’s stopped with
this spring-loaded pin.
This not only ensures ideal alignment with
the records and record take-out arm
(and its grabby thing)
but also with the cancel pins
of the readout arm.
Ideally, the feeler switches will be adjust
so that the carousel stops a bit prematurely,
and the lock solenoid pushes it a little bit
farther.
This ensures the readout switches are firmly
against the pins and make consistent contact.
Now, here’s where the cleverness of electromechanics
comes into play once again.
You’ll notice that only one of these cancel
solenoids moves.
And there is only one cancel switch inside
the Wurlamatic to make that happen.
Why didn’t they both move?
Well, because the current path between the
cancel switch and these solenoids goes through
the side 1 and side 2 relays.
Only the solenoid representing the side currently
being played receives power,
thus only that selection is cancelled.
It’s simply a matter of running the power
through one of the normally open contacts
of the relay, so that whichever relay is currently
being energized
(thus, the side that’s being played)
will provide a current path to the
corresponding cancel solenoid.
You might then ask, what happens if someone
selects both sides of the same record?
Won’t the side one and side 2 relays both
be energized?
Well, no!
Why?
Because side 1 takes precedence over side
two.
How?
Because the side 2 relay is wired through
a normally closed switch contact
inside the side 1 relay.
In this way, side one and two are interlocked.
If both of the readout switches are activated
simultaneously, both relays 1 and 2 are receiving power.
But, if relay one is energized, it cuts off
that power to relay 2.
This in turn means that the Wurlamatic will
grab the record, pivot to play side one,
and cancel the side 1 pin and the side 1 pin only.
Because remember;
Relay 2 is not powered whenever Relay 1 is.
Relay 1 disconnects power from Relay 2.
So, down comes the cancel solenoid, with its
power output being directed through relay 1,
and now once the cancel solenoid is released
the side 1 readout is released as well.
This now de-energizes the side 1 relay, which
means, now the side 2 relay can be energized
by readout 2.
The result of that is that once side one has
been played, the tone arm will hit the trip switch,
the Wurlamatic restarts to put the
record back,
but with the side 2 relay now energized, the transfer switch is out of the picture
and it immediately takes the record back out again.
This time it pivots to play the other side.
Now, when the Wurlamatic hits the cancel switch
for the second time, the other cancel solenoid fires,
and puts the side 2 pin back.
Now neither readout switch is activated, and
so neither are relays 1 or 2.
When side 2 is over, the trip switch is hit,
the Wurlamatic starts back up, and without
the side 1 or side 2 relays in play anymore,
as soon as the record is put back,
the transfer switch stops movement of the Wurlamatic,
the record jaw thing hits the safety switch,
and the carousel starts rotating, looking for
the next pin and thus the next selection.
Once the carousel has made one complete rotation,
this catch on the end of the readout arm hits
the latch mechanism near the override magnet.
This doesn’t yet open the override switch.
Instead, the carousel will go on for one more
rotation.
This is done in case it was, say, playing
F3 and you then selected C2.
C2 is behind F3 so it's gonna hit this before
it gets there.
Once it hits the override mechanism a second
time, that switch will open,
and now the jukebox is back to its standby state.
Did you get all of that?
It’s simple, right?
Let’s go through all this once again, just
for funsies.
We begin with the latch solenoid.
The latch solenoid is held in because the
machine thinks it has a credit so relay 1,
which is different from the side 1 relay
- why did Wurlitzer do that? -
is energized.
Pressing a letter button and a number button
closes these leaf switches which in turn activates
relay two, which gets the selection accumulator
motor started.
Once the magnet arm leaves its park position,
the wiper contacts will complete a circuit
to relay 3, so it will keep going.
The combination of letter and number puts
voltage across the letter and number patches
on the board of the selection accumulator.
Once the electromagnet is behind the corresponding
selection pin, the magnet fires, pulling the
pin towards it, unseating the pin from its
catch, and it pops up.
When the magnet arm is back at its park position,
the circuit to relay 3 is broken, which stops
the magnet arm.
At the same time, power is interrupted briefly
to the latch solenoid somehow
(still not clear on that one)
to pop the selection buttons back
out, and a pulse of power is sent to the override magnet,
closing the override switch, thus
causing the carousel to be unlocked
and begin rotation.
Once either readout switch hits a pin, this
energizes its corresponding side relay.
That will cut power to the magazine motor
and its lock solenoid, locking it in place.
It also provides power to the main cam relay,
causing the Wurlamatic to remove the record
from the carousel.
Shortly after it’s moved, the transfer switch
keeps the main cam relay powered, which is
important because the cancel switch will fire
the corresponding cancel solenoid,
pushing the selection pin back down, and thus de-energizing the side one or side two relay.
At this point, the carousel will not be able
to move because the safety switch is not being
depressed now that the record take-out arm
is away from its parked position.
Once the record take-out arm is in the play
position and the stylus has been moved to
play the record, the play switch is depressed,
pausing the movement of the Wurlamatic by
de-energizing the main cam relay.
Now the record can play.
When it’s over, it hits the trip switch,
bypassing the play switch and re-energizing
the main cam motor once more.
Now the record take-out arm will return to
the record carousel, and assuming the pin
was successfully cancelled and thus neither
the side 1 or 2 relay is still being energized,
the record grabby jaw thing will open up, hit the safety switch, and the carousel resumes movement.
If another selection is stored in the selection
accumulator, it will of course stop once more
and repeat the same sequence.
However, if there are no more selections,
the carousel will hit the override assembly once,
and make one more rotation.
After completion of the second rotation, the
override switch is opened, stopping the carousel,
and now the jukebox is back in standby mode.
So.
Is this neat or what?
I mean, wow.
I love the way this thing works.
It’s endlessly fascinating to me, and even more
so when you remember that there is not a single
programmable logic controller residing in here anywhere.
Speaking of, I’d like to address a bit of
apparent controversy with the titling of the
last video.
And possibly this one.
I don’t consider this device to contain
a computer.
But, some people would say that it is a computer.
I disagree, but first let’s acknowledge
that electromechanical computers are a thing!
There’s no reason you can’t create a fully-functional computer using nothing but relays.
But, I don’t see this device as computing
anything.
It has a set of instructions, sure, and what
do computers do but follow said instruction sets?
But at the same time, would you call an internal
combustion engine a computer?
It has a cam shaft which opens its valves
in time with the movement of the piston.
And in that sense it was programmed, but the actions
are entirely mechanical.
There’s some nuance to be explored here,
but I would consider a sequence of operations
to be separate from computing.
Now, you could kinda argue that this machine
does multiplication in the selection process…
but I don’t know if I’d agree.
The one thing it does actually compute is
the value of coins.
I would consider the credit accumulator to
be an electromechanical computer, although
a very basic one.
And even then, it really just counts up and
counts down, with each step being controlled
with relay logic.
And that’s where this gets messy.
This machine is undeniably full of relay logic.
In that sense this does have a programmable
logic controller.
The programming was just done in what today
we would call a very unconventional fashion.
Perhaps it would have been better to say silicon-free
computing, but let’s be honest.
When you say the word “computer” these
days -
this is not what comes to mind.
Well, thank you so much for watching!
I hope you liked this video.
To answer a question I’m sure many of you
are wondering, yes.
This is my jukebox, and I’ve had it for
years.
It’s been at my parent’s home all this
time, and also kinda non-functional for the
past half-decade, which is why I’ve never
featured it.
One thing I do need to track down are suitable
replacement springs for the selection accumulator.
A number of selections just don’t work because
the springs were broken, likely since the
bottom panel of this machine has always been
missing.
The broken springs are all on the side that
faces the rear, suggesting they were
damaged through careless handling.
This jukebox is actually what turned me into
the weirdo I am today.
My parents let me buy this thing when I was
in -
wait for it
- middle school.
Yeah.
And I could afford it with my chores allowance
because it was very ugly and very broken.
The person who owned it previously didn’t
have any interest in fixing it, so it went
on eBay for cheap.
I owe my parents a lot of thanks for things
that have happened throughout my life, but
their willingness to let me buy a broken jukebox
at the age of 13 is certainly high up on my list.
So, thanks mom and dad!
And now, it’s time for me to end this video.
But!
There are a lot of interesting features of
this jukebox that we haven’t covered.
Be on the lookout for a third jukebox video at some point,
but for now, thank you.
Thanks for watching.
Thanks to everyone supporting this channel
on Patreon.
And thanks again to my mom and dad.
Cue the music!
♫ gratefully smooth jazz ♫
We’ll make one more take of that… then
we’re moving on.
‘Cause this is a LONG video.
I left you with a devas… eugh.
Gonna be doing this ‘till like 1:00 in the
morning.
This...
oh sh*t…
sh-oops,
I said a bad word…
One more take of that.
Ths only weights like 15 pounds, and has sharp
edges, no big deal at all
That’s a longer line than I thought, my
word
That’s so every corr…
every?
Where did that word come from?
Well it was earlier but not there.
From my descriptions of what’s going on
here, I’ve been relying on...
And I forgot to put my finger in the thing.
Ohhhh boooyyyyy…
So, how confused are you?
Seriously, I hope that wasn't too bad.
Also, totally wasn't thinking about how much these captions would get in the way of some things on-screen.
Pro-tip! On desktop, you can click and drag these captions around to wherever you'd like. So there's that.
Sorry, mobile users :(
