IBM 727, Manual Of Instruction

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then be zero. (Turning screw clockwise causes track C to lead track 1 with tape
moving forw a rd .)
6. The fluctuations in skew (flutter) may not exceed 6 usee, otherwise tape guid­
ing must be improved. (See sections 13. 3 .3 , 13.3. 5 and 15.2. 5.)
7. After the master tape is rem oved, readjust the pre-am ps to give 20v peak-
to-peak output from tape written on the same machine.
8. With the present master tape it is possible to compare the C track output of
a given character with the 1 track output of the preceding or succeeding character in­
advertently, and therefore adjust for 6 7 .2-usec skew. Consequently, if there is any
doubt as to the previous head alignment, or if a new head is being installed, an inter­
changeability test should be run after making the skew adjustment.
As a check oh the above method one may observe the read bus itself on the scope
while still syncing on the first bit. The method of syncing on the read bus and observ­
ing the peaks is necessary when using the tape drive tester (section 19.4 .3) but is not
as accurate.
15.3 HeadWear
The entire head assembly (P /N 333072) should be returned to factory for servicing
if there is irregular wear on the surface of the head and laminations sufficient to pre­
vent intimate contact of the tape with the head. This condition causes a signal of less
than 30mv, peak-to-peak across one coil of the head (on one or m ore tracks), when
tape written with that head is read.
The head should also be replaced when there is a signal of less than 30mv, peak-
to-peak across one coil of the head (on one or m ore tracks), because of uniform wear
of the head and the laminations.
15.4 REMOVAL AND ADJUSTMENT OF TAPE CLEANER
The best procedure for removing and adjusting the tape cleaner is as follow s:
1. Remove the lower head cover.
2. Extract the pin from the side of the light housing and drop out the light.
3. Remove tape cleaner.
4. Mount tape cleaner, leaving screws loose.
5. Run the head cover down as far as it will go and remove upper cover.
6. Push the tape cleaner assembly up toward the upper head cover as far as it
will go. Lay the gage block (P /N 460961) between the cleaner and the read-w rite
head. Position the cleaner so that the gage block is in the position shown in Figure
20, but never as in Figure 21. Hold the cleaner firm ly while the mounting screws are
tightened. Be very careful when positioning the cleaner block to prevent damage to
the cleaner blade.
7. Adjust and gage the spacing between the photo-cell head assembly and the
tape cleaner as shown in Figure 19. Move the photo-cell head assembly up or down
to make this adjustment.
8. Tape break indicator. The reflector plate on the tape cleaner block should
be adjusted so that light is directed on the photo cell (tape indicator side) to produce
a maximum voltage swing from a dark to a light condition (from tape existing between
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