DonNews #21 27 марта 2005

Железо

REPAIR - We continue to repair the Pentagon ...

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REPAIR



         Poor reading a floppy disk.

(C) Wild / oHg

 The reason may be the fault circuit
phase adjustment. Phase adjustment circuits assembled on chips 
D92 and D93.  Verification is performed without IC

1818VG93. Check the flow of impulses
4 MHz to the element D93 / 3. Connect the drive, insert a 
floppy disk with the recording, lower drive heads. Check 
transmission RDD pulses with the drive to contact A21

connector, then D92/2-D92/5-D85/8. You should see a pulse 
frequency of about 4 MHz, which should appear on the findings 
of D93 / 9, D93/11 and D90/27. Now slow down a finger motor 
drive - in this case the pulse duration on the findings of D92, 
D93, D90/27 should vary depending on the

engine speed. If so,
the scheme of the phase adjustment is working properly. Cause 
of poor readers can be insufficient duration of the pulses

with a flip-flop D92. Then increase the capacity
capacitor C1 between common wire and the terminal element D92 / 
5. You can also change conversion factor circuits D93. For

This cut output D93 / 3 of all the wires and switch to +5 V.