www.newsandtech.com
In a previous article I shared several ideas that would
help press operators resolve press drive surging.
Some motor problems that could cause this
condition are shorted armature
windings, missed wired shunt field
windings, insulation of the wind-
ings breaking down and worn motor
brushes or weak brush springs.
Recently, I encountered another
press surging problem I had never
experienced before.
The newspaper's press
would surge throughout the
press run and would finally
come to a complete stop. The
press operator would then turn the dampen-
ing system on and off until the press would run
again.
Was the dampening system affecting the
motor controller since it was so close to the
trigging circuit?
No. What did happen was that the damp-
ener contactor was vibrating the back plate,
upon which the motor controller's electronics
were mounted. And upon that plate was the
armature feedback circuit. Although the two
fuses in the circuit tested OK, they had become
corroded enough to create a non-conductive
surface between the end of the fuse and the
fuse holder.
The only way to solve this problem was
to find out -- using a voltmeter -- where the
feedback signal was being interrupted.
In the event you encounter a surge prob-
lem, consider removing each fuse from its
holder, then remove any corrosion you find
from the fuse and holder with an emery cloth.
Keep in mind that the corrosion is not that
evident. It will appear as a light discoloration
on the ends of the fuse.
Wild motor fluctuations also sometimes
occur as a result of misadjusted motor control-
lers.
Check the door
I recently worked on a press that, when it was
configured as four units, worked fine. But once
the newspaper added more units, the machine
would fluctuate wildly if press speed was al-
lowed to advance rapidly. If the press drive was
advanced very slowly, it would fluctuate for a
moment and then stabilize. The problem? The
gain was set too high. The isolation scaling pot
had been misadjusted. The press drive re-
sponded properly once the gain was reduced.
In another instance, I was asked to trou-
bleshoot some motor actuators on some Goss
Metro and Metroliner presses (ink control mo-
tors for the page pack system).
The predicament: Column switches
appeared to work intermittently and failed
to cause the appropriate motor actuator to
respond.
It was a difficult problem to diagnose
because the switches would work correctly at
times.
After careful and persistent troubleshoot-
ing, we were able to determine that the ink
column board PC connector had a loose wire that
wouldn't work whenever the control door was closed.
Once the door was open, the wire made its connec-
tion and the actuator would perform as designed. The
lesson: Check the connection first if you are experi-
encing this problem. The wire connector makes its
connections in the same way as trailer connectors.
It's made when the insulated wire is forced
between two flat sharp metal posts, which causes the
insulation of the wire to be cut, thus exposing the wire
to the metal post.
Forcing a small screwdriver down on each wire
causes the wire to move between the metal posts,
making the wire form a better connection with the
metal posts, eliminating any intermittent connection
issues.
frank bourlon is the executive and training director for the
Newspaper production and research Center. he can be
reached at fbourlon@np-rc.org or 405.524.7774.
pressMaN's ToolBox
By fraNk BourloN columniSt
Intermittent electrical problems and how to solve them
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Newspapers & Technology November 2009 9

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