Installation, Operation and Service Manual
LKP Series
© 2016 DynAmp, LLC
Page 19
041738 I
A. The dc voltage range may be as high as 75 Vdc (see “D” below). Make certain the
voltmeter being used is set to measure average dc volts in this range.
B. The measured bus and all other high current buses in the vicinity (within a 10-meter
radius) should be operating at or near their highest levels. Note: All magnetic field sources
will affect the channel voltage readings.
C. Make a photocopy of table “Form for Recording Channel Voltage Measurements”. The
initial readings are made as instructed on the form, and are recorded in the individual
blocks. Refer to the head schematic drawing in the back of the manual, which graphically
show the channel locations on the head.
D. Excluding the effects of external magnetic sources and assuming a full rated bus current,
each channel is expected (by calculation) to measure approximately 20 V to 35 Vdc. In
practice, channel readings should be more on the order of 10 V to 30 Vdc, but that may
not be achievable. A channel failure will usually be indicated by either a full-off (near
zero), half-on (35-38 V) or full- on (70-75 V) condition.
CAUTION
Avoid operating the unit for an extended time with any channel output over 40 V. This
will permanently damage the system. For voltages over 40 V, consult the factory.
E. If any of the channel readings do indicate trouble, refer to Theory of Operations and
Maintenance & Spare Parts sections and resolve the problem; then proceed with
"Magnetic Centering".
Note 1.
Low Readings: A very low amplifier output voltage may be normal for certain
channels; however, ripple can be as high as 3 V on a non-operating (full-off) channel.
Thus, a very low reading (i.e., 1 V to 3 V, should be suspected as a possible problem;
subsequent head movement or other magnetic change may show that the channel is
operating properly.
Note 2.
High Readings: The maximum allowable channel output of 40 V relates to the
maximum heat dissipation that the channel can safely handle. A reading of 30 V to 40 V
makes a change in head position highly desirable. A reading exceeding 40 V makes a
head position change necessary. A reading of 70-75 V indicates a full-on channel
condition or a blown channel fuse, and requires immediate action to resolve the problem.
A reading of 35-38 V when immediately adjacent channels are significantly different may
indicate that one of the two SCRs in the channel has failed.
5.10 MAGNETIC CENTERING
The distribution of load, or heat, among all channels will be optimized by magnetic
centering of the head relative to both the bus and the total magnetic environment of the
head. In general, this simply means moving the head so that channels with high voltage
readings will be farther from the bus, and channels with low readings will be nearer the
bus. Whether or not the head should actually be moved depends on three factors:
A.) The possible impracticality or difficulty of moving the head because of support-system
requirements, clearances available, etc.
B.) The necessity of moving the head because of voltage readings that are too high or too
low for certain channels.
C.) The desirability of moving the head to obtain a better balance of channel voltages.
