When you have the complaint that the thrust reverser does not extend upon selection, checkout the spring inside the control stand thrust lever handle. It is possible that the spring which operates the control switch S828 (eng#1) or S829 (eng#2) is broken. The spring can be found in the CMM 76-11-07 page 1019.
Secondly, when activation of the T/R gives you no T/R deployment and it gives you the overhead REVERSER light, checkout the adjustment of this same spring. Bad / critical or (worn) spring adjustment can give you this complaint during QUICK movement of the T/R handle (common pilot input). It then operates the switch but de-activates again with the T/R handle fully pulled rearwards (selection). With SLOW movement of the T/R handle this complaint is not there, giving you false hope. Re-adjustment of this spring is then necessary (AMM 78-34-04-700-801) , giving it a more positive input to the microswitches S828 or S829.
See pictures below for more clarification.
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