Rock-Ola 1454

This machine had a couple of interesting faults. The first problem was that it didn’t detect any selections. Once a selection was made it just run the magazine back and forth without stopping. There are several things that could cause this behavior and I made some measuring hoping for an easy fix, but not… I found an open circuit in the wire connecting to the carriage assembly.  This wire rotates round the magazine shaft following the carriage round the selector unit. It held for 60 years but now it was worn out.

I searched the internet trying to find a recommendation of a replacement wire but didn’t manage to find anything about it. Instead I found a wire at a car part retailer. This wire is not as soft and flexible as the original one and will probably not hold for another 60 years but I expect it to hold for many years to come.

When replacing the cable I made new cable clips out of metal stripes covered with shrink tubing. The old plastic clips were too brittle to be reused and the inner one was broken and had to be replaced.  

The second problem was that the magazine sometimes stopped to rotate and to get it to go again the gripper motor had to be manually turned for a couple of turns. This fault was very intermittent and has been in the machine for quite a while. A couple of years ago it also caused all records in the machine to be destroyed. What’s happening is that while the magazine motor rotates the magazine also the gripper motor rotates, very slow, causing the gripper to start closing against the records.  The records was destroyed when the inner gripper meet the records in the rotating magazine. All records looked like packman before the owner managed to cut the power to the machine. There is actually a built in protection against this type of disaster, more about that in a little while.  

 

The cause for the gripper motor to turn at the same time as the magazine motor was the interlock relay in the control box. The interlock release contact in the diagram above is actually two switches in parallel, to ensure that the gripper motor is properly shorted to ground. When checking the switch with the continuity setting it was fine but when measuring the resistance it was about 25-50 ohm. This caused a voltage drop over the switch that was enough to drive a current through the gripper motor causing it to slowly rotate. The protection mentioned above is the Safety micro switch in the diagram. This switch is located at the cam at the gripper drive shaft. The function is to cut the current to the magazine motor before the gripper reach the records. That’s what happened when the magazine stopped and the gripper motor had to be wound back to get the magazine to turn again. In this machine the Safety micro switch was misaligned and didn’t stop the magazine motor before the disaster was a fact. This fault could have been in the machine for a long time, maybe even since it was brand new. As long as everything works as it should then the Safety switch doesn’t matter, but when it goes wrong it’s worth its weight in gold.  

 

 

I visited another 1454 with an interesting problem a little while ago, related to the cable clips at the selector arm. This machine did stop the magazine slightly wrong causing the gripper to miss the records, but only at lower number selections and when the magazine was running clockwise. The cause turned out to be the outer cable clip. It was broken and at a certain point the carriage cable wedged between the arm and the solder lugs at selector unit forcing the selector arm inwards and the screw head that pushes the carriage slipped of the top where should rest causing the magazine to stop slightly wrong. A new cable clip and the machine worked fine again.