Shugart SA455 - 5.4.3 Head Amplitude Check

50mV
50 Jtsec:
50 mV
50,tsec
50mV
AZIMUTH
+ :~1 MINUTES
AZIMUTH
oMINUTES
50 mV
AZIMUTH
-18 MINUTES (SA455)
-21 MINUTES (SA465)
FICJURE 5·8. AZIMUTH CHECK
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5.4.3 Head Amplitude Check
Ith~se .. ·.·.CheckS are .. only valid when writing and reading back as described below. Ensure the diskette used for this
t'check}s not "worn" or otherwise shows evidence of damage on either side.
a. Install good media.
b. Start motpr.
c. Select drive and step to track. 39 (SA455) or track 79 (SA465).
d. Sync oscilloscope external on TP7 (+ Index); connect one probe to TP2 and TPI on drive PCB.
Ground probes to PCB, ADD, and invert one input. Set volts per division to 50 mV and time
base to 20 msec per division.
e. Select head a and write a 2F pattern on entire track. Average minimum amplitude peak-to-peak
should be 100 mV.
f. Select head 1 and write a 2F pattern on entire track. Average minimum amplitude peal<-to-peak
should be 100 mV.
g. If either head falls to meefmlnlrnum amplitude spe!clflcatlons. continue with procedure.
h. Install fresh media andrecheck.
i. Checl<motor speed as per pi:uagraph 5.4.6.
j. With oscilloscope In"chop" rnode,:verlfy that output exists atboth TPI and TP2. If one TP has
no output. or significantly les~.output than otherI turn head cable connector over at J4. Should
same TP have little or no output, pes Is faulty and needs replacing. If opposite TP now exhibits
problem, head assembly Is atfaulLand should be replaced. Refer to paragraph 5.5.3.
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