Rockola 451
8.11.2005:
I finally got another jukebox, after having long regretted selling my previous one.
This 1973 Rock-Ola 451 is a fine machine to spin some vinyls with.
Compact size for even small spaces
The jukebox looks a bit dark, both fluorescent tubes are missing. A visit to lamp store is in order.
Inside is neat
As in all Rock-Olas that have been long in storage, the gripper mechanism was a bit stuck and did not
always grip the record. The lubricant vaseline has dried and turned into gummy stuff. Cleaning and putting
in new lubricant fixed it.
Lights on
A fine machine this is. Putting in 60 cm fluorescent tubes instead of original 71 cm ones required
some modifications, but the 71 cm tubes are almost impossible to find. It is only 5 cm (two inches)
on each end so you will never notice the shorter tubes outside.
10.11.2005:
Old grommets and a bagful of new
Some rumble in the sound made me suspect the turntable motor mounting grommets. After all they are
over 30 years old, and were very hard. No wonder the motor vibration was not dampened. 3/8" pinball
rubbers made fine replacement grommets. No more rumble!
Motor hangs from three places
At the same time, I cleaned and re-oiled motor axle and bearing, and the idler wheel. A drop of
good oil ensures smooth running for some years.
27.11.2005:
It's Sunday and as usual, nothing much to do. So I decided to tackle a problem in my Rockola. When
first turned on, one or two first records sometimes stay on the turntable after ending. I have already
cleaned the gripper open/close mechanism, so the problem isn't anymore in the gripper not closing fast enough.
So let's examine!
OK, the gripper closes fast enough, but for some strange reason it jumps upward right before closing, and
misses the record. I found the problem to be in the two gears that control gripper movements. They are in the
same shaft, one of them moves gripper and the other closes it. There were so thick layer of old grease, now
turned into bubble-gum like mess, that the gears were sticking, and when the gripper closing gear rotated it
moved the other gear just a little bit, but enough that the gripper jumped a few millimeters up. After a few
spins and warming up, the grease softened just enough that the problem went away. Removing gears, cleaning them
and putting in a thin layer of good fresh grease solved the problem for hopefully a long time.
29.11.2005:
There are clear instructions in the manual, on how to adjust amplifier operating point or bias current.
I checked those, but only very minor adjustment was needed even though the amplifier is over 30 years old.
While the amplifier box was open, I went through all electrolytic caps with an ESR tester, and as a result,
replaced a handful of dried capacitors. Before this, the system had a slight hum for a few seconds after power on,
but now it starts up quiet.
Amplifier is easy to service when open.
And the Sunday cleaning job was a big success. No records have been missed by the gripper since. :)
Gripper gears in the center of picture.
3.1.2006:
The idler wheel that spins the turntable, was a little bit worn. That caused the turntable to lose speed
when loaded. I bought a small bottle of glycerol, and soaked the idler wheel in it for overnite, and that did
the thing! Glycerol softened the rubber and also made it slightly larger, and now there is plenty of torque
and the turntable does not slow down even if braked with a finger.
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