Write Malfunctions; Write Circuit Troubleshooting - IBM 2310 Maintenance Manual

It
will be necessary to turn off power to the
drive motor to reduce disk speed to 30 RPM to re-
set the latch -- then power up the machine to attain
a File Ready status.
WARNING: Do not put scope probes, leads, or jum-
pers of any kind on lines comming directly from
read/write heads. The heads can be damaged and/
or data destroyed by the presence of voltages at
these points.
The read circuits consists of read/Write heads,
the Preamplifier/Write Driver SLT Card, Read
Amplifier SLT Card, and Data Separator SLT card.
All cards are located in the electronic gate.
The preamplifier circuit provides a differential
signal input to the read amplifier of 360 KC (all zero
pattern) and 726 KC (all one's pattern). The output
. from the read amplifier is single ended, and provides
double frequency data to the data separator SLT card.
The read gate is the only gate required by the read
amplifier.
A CE Test Point and is located on the read am-
plifier for CE use. Input to the amplifier differen-
tiator circuit is measured at the CE Test amplifier,
TP D2 G07. Output of the detector circuit is mea-
sured at pin location n2 B03.
The voltage at TP D2 G07 should be 1. 5 v mini-
mum to 3. 15 v maximum. This voltage will vary
with respect to the track being read. A higher volt-
age will prevail at the outside track than at the in-
side track because of the difference in disk surface
speed relative to the read/write head.
The following analysis is to be used to trouble-
shoot read circuits: Oscilloscope display patterns
for read/write circuits are shown in Figure 1-1.
Both Heads in 2310 Fail to Read - Probable causes:
1. Heads not loaded. Check visually.
2. Carriage at incorrect cylinder to read disk.
Check visually.
3. DC voltage supplies not at a correct level. This
is an unsafe condition. Check interlock SLT card.
In a read select mode, the write lock latch
should be set.
NOTE: Voltages should be checked at the SLT board.
4. Head not selected, or both heads selected. Check
head select line (+3 v level for head zero and
ground level for head one).
5. Data separator circuit has improper output.
Check for Read Clock output on C2 D03 and
Read Data output on C2 D05.
6. Read amplifier has no output. Check for output
signal at detector circuit on read amplifier SLT
card at location D2 B03.
1.2
7. Read amplifier has no input. Check for pres-
ence of input signal at Amplifier Differential
circuit on read amplifier SLT card at CE Test
Point TP D2 G07.
2310 Reads But Generates Read Errors - Probable
Causes:
1. Machine fails to read on a particular head:
a. Head select transistor for this head is in-
operative. Check write driver SLT card
for malfunction of head select transistors.
b. Line noise present in read signal. Check
that head-arm assembly is electrically
isolated from frame ground.
c. Open head diode(s). Replace preamplifier/
write driver card.
d. Disk speed detection output fluctuates. Check
for sector time of 5 ms between pulses.
Possible that speed detector is defective.
e. Data separator circuit defective -- does not
provide Read Clock output at C2D03 and/or
Read Data output at C2D05. Check data
separator adjustment of 600 nsec single
shot which gates between clock pulses to
permit data pulses to pass.
f. Head shoe dc resistance relative to base
plate should be 5 ohms or less.
g. Intermittent short between coils, or between
coils and ground of read/write head.
h. Heads improperly aligned to read track.
2. Machine makes frequent read errors on a par-
ticular head.
a. Disk Speed detector output fluctuates.
Check for defective speed detector.
b. Weak read signal at head. Check for im-
proper loading of head against disk surface.
Check for defective head. Check for im-
proper force on head-load spring.
c. Head shoe dc resistance relative to base
plate should be 5 ohms or less.
d. Bad head. Check for presence of read
amplifier output at pin location D2B03.
e. Intermittent open in head diodes. Replace
preamplifier/write driver SLT card.
f. Intermittent head select. Check write driver
SLT card for malfunction of head select circuit.
g. Head is out of alignment. Check alignment
of read/write head with CE track 100.
1.4 WRITE MALFUNCTIONS
1.4. 1 Write Circuit Troubleshooting (Figure 1-1)
NOTE: An apparent failure to write can be caused
by a write select error condition when the Write Lock