Rockola 440 Update

Hey All,

So here is an update with my Rockola 440.

I replaced the two motors and they seem to be working fine. Things
are progressing. Thanks again for all the help.

Now on to the next issue. One of the read out hammer coils is getting
warm. It's not staying energized or locked on, it's just getting warm-
in the relaxed position. I measured the resistance and one coil
measured 30.7 Ohms, the other measured 31.2 Ohms. This seems ok.

I looked in the control box and the 15-Ohm resistor attached to the
release coil measured open, also it basically fell apart when I
removed it. I replaced it with a 22-Ohm resistor--it's all I had with
the intention of testing it briefly.

I put a credit on the jukebox, made a selection, record is selected,
both magazine and gripper mechanisms work as they should. During the
play cycle (still no sound but that's another topic), I noticed that
the one read out hammer coil was getting warm again and the 22 Ohm
resistor is starting to smoke.

I quickly turned the machine off. When I turned it on again, I tried
canceling the record playing using tone arm switch but it does not
work. I had to manually latch the release coil, in order to initiate
the cancel operation which again, both gripper and magazine motors worked as they should.

I should note that if the machine is in OFF mode, the coil does not
get warm.

Can anyone help?

Thanks,
Robert

Hi Robert,
What you are going to need to do is, using the schematic, first verify how that coil is energized. I suspect that it always has voltage, and is supplied with a ground when it should actuate. If what I suspect is true, you need to follow the wires back to the ground source, looking for a "pinched wire".
If it is always grounded, I would look for "burned-shorted together" wires someplace in the chain---
As to why you have "lost" the cancel --once again--schematic time, to see what actuates the relay--
Ron Rich

Hello Robert

Do you have the manual ?

I have just had a quick look at the schematics I have for my 474 machine. Which is very very similar electrically.

What I think is happening is this.

The 15 ohm resistor is actually used to slow down the gripper motor towards the end of its transfer cycle,
thus preventing the tone arm from moving too quickly towards the record.This resistor is switched in series with the motor
by micro switch number 2 the tonearm movement is operated by the gripper motor of course.

If you check in the manual at the "Transfer Complete Sequence 18" section.
I think that your mechanism is not fully completing this cycle.
The hammer reset coil is left energised (which explains why it is getting hot, and the
gripper motor is still energised although now at the end of its travel, it is therefore stalled
but with its power being supplied via the 15 Ohm resistor hence this is burning up.
If this resistor was open, then I think the gripper motor would stop short of it's cycle, and the tone arm would not move.

This whole sequence should be completed by the operation of Micro Switch 3 on the back of the gripper assembly.
This micro switch should operate the interlock release coil. Which will cut power to the motor and the hammer reset coil,
as well as preparing the machine for the end of play cycle. You have already proved this part to work by operating the release coil manually.

So check the resistance of the release coil, the micros switch. And according to my diagram there is also a 47 Ohm resistor in series with this coil.

You really do of course need to study the manual to fully understand how this process works.

Hope this helps

Pete

Hey Guys,

I had some time to take another look at this.

Ron: I couldn't find any shorts, burnt or pinched wires.

Pete: The micro switches all test OK. FWIW, my machine has a 60 Ohm resistor in series with the coil instead of a 47 Ohm.

However the Trip coil resistance measures 68 Ohms and the Release coil resistance measures 253 Ohms. That can't be right. Does that mean my Release coil is bad?


Robert

Robert,
Does the release coil energize ? If a coil energizes, it's usually OK---
HOW did you "test" the MicroSwitches" ?
Ron Rich

Hi Ron,

The release coil appears to energize BUT only when I temporarily connect micro switch tab common to tab #3. Otherwise it does not energize. That and physically moving the coil latch are the only way I can cancel the record. FWIW the tone arm leaf switch is connected to micro switch tab common to tab #2.

First I tested the continuity of the tabs on the micro switch during the switching action. I also bought some new replacement micro switches and put one in to see if I had the same problem. No change. I tried to cancel a record with the tone arm switch but it still doesn't work and the 15 Ohm resistor in series with the release coil still gets hot.

I also looked at the power supply to see if there were any signs of shorts but everything seemed ok.



Robert

Robert,
Since the relay energizes, I would not suspect a bad relay coil.
The resistor remaining "hot" would make me suspect something in the circuit that stops the motor is failing to "shut off"-- Once again--I suspect a Microswitch--how did you "check" them ?
Ron Rich

Hi Ron,

The way I checked the #3 micro switch was with a built in continuity tester setting on my DMM. If there is a connection or contact, the meter will beep, if there is no connection the meter will not beep.

When the switch lever is down, tabs 1 and 2 are connected and so the meter should read continuity, when the switch lever is up, tabs 2 and 3 should be connected and the meter should respond accordingly, which it does.

I tested this functionality in the other switches and they test the same. I even purchased a bunch of new switches just in case and they test the same. Unless there is another way to test the micro switches. I'm guessing that they are all good. I even replaced the micro switch with one of the new one's but still had the same problem.

I just thought of this. I've been looking at #3 micro switch as being bad, maybe I should be looking at #1 or #2?


Robert

Robert,
"Digital" meters will NOT test switches properly. An "analog" meter set on a low range, is needed. The digital will show you on/off functions only but usually can not "see" how well the contacts are "making". I suggest that you replace all switches, if you do not have the correct meter. Ron Rich

Hi

Since you have checked the circuit and latch coil by shorting the tabs on the microswitch. Then you either do have a bad microswitch as Ron has said,
or the alignment of the microswitches to the cam is incorrect. Maybe the cam is not fully reaching the end position (a jam maybe).
You must check that once the tone arm is on the record and music is playing, that the microswitch has physically operated.

Why not let the machine get to almost to the play position (say the gripper has the record and is halfway towards the turntable). Then put the operate switch into off, and remove the power to the whole machine. Then with a multimeter attached to the relavant tabs on microswitch 3 rotate the gripper by hand to completely finish the cycle (ie record on turntable and tone arm on record). Do this by rotating the knurled knob on the gripper motor shaft.

Doing it this way will allow you check the microswitches for correct operation. You may need a small mirror of course, and maybe a helper to turn the motor while you look at the switches.

Pete

Pete, and Robert,
I think Pete has a good idea here--but I would approach it a little differently.
I would allow the gripper motor to place a record on the TT, and shut off the power at that point. At which time I would look at all the switch actuators. All should be fully in or out of the cam "dips". If turning the motor by hand moves one or more in, or out, of a "dip", I would turn the motor a bit more, and see if the record will now "reject" when powered on. If so, I would replace/re-adjust the switch that seemed "out of place"-- Ron Rich

Hi all.

Yes I agree with Ron on that point.
There is just one thing that concerns me, and that was that Robert says the 15Ohm resistor is burning up.
I think that 15R resistor is in series with the gripper motor at that point, I therefore suspect that the motor has stalled.
Therefore it would very difficult to turn it any further with the power on.

So I would therefore do as Ron says, but when the record is on the TT and tone arm has been placed. Then shutoff the power and check the micro switch actuators as Ron
has said.

Trying to solve these types of faults is so difficult by just talking
One look and I am sure we would have this sorted.

Pete

Edit
Sorry Ron, I will shut up and get my coat
That's exactly what you said above.

Pete,
No problem--like you said--it is difficult to trouble shoot, with out 'seeing" the problem--
I too, suspect the motor has stalled (but failed to state that ). But I don't know why--so I suggested powering it off and seeing if it could be moved further, or if it had traveled to it's limit. Knowing the answer to that question, I hoped that I could "pin-point" the problem--
Ron Rich

Hi Guys,


SUCCESS!

I was going to make a video to you so show the operation of the cam unit and I took a closer look at it. It turns out that the cam was NOT aligned properly. Looking at the 'home" position the switches seemed correct however the #3 switch never fell into the cam slot so that switch always stayed in one position. That didn't make sense so I re-adjusted the cam according to the manual and it now works perfectly.

My only two problems I have now are the home position is a few selections off and the sound is coming from the right side speakers only.

Thanks again. I really appreciate the help guys!


Robert

Robert,
Glad you "gott-it"---but I'm curious ??
What makes you think it is a few positions off of "home" ?
Ron Rich