Editing PDP-11/70 Troubleshooting Guide (section)

== Known faults from DEC's tech tips ==
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+ '''Selected field changes and tips (KA-K1170-MG-003, pp. 20 to 23)'''
! Symptom !! Cause and fix
|-
| Intermittent data parity errors || Green bypass capacitors on M7984 modules burn up; replace M7984s with burnt capacitors
|-
| Transient data parity errors in other core stacks on the same side || National Semiconductor NS7520 sense amplifiers on G116 modules generate spikes; replace G116s fitted with them
|-
| Unreliable connections on over-the-top cables || H224 cables damaged by inserting and removing neighbouring modules; replace or re-crimp
|-
| SACK timeouts, trap 0s and Unibus timeouts || 74123s from some vendors in the M8136 timeout logic not clearing properly; replace E15 and E25 with Texas Instruments 74123s (DEC 19-10436)
|-
| Poor power distribution || Replace power harness 7009540 with 7011051 (FCO PDP1170-R1)
|-
| H775-D breaker trips during power fail (MK11) || M8160 revision update (FCO M8160-R4)
|}
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