_ DEC-O-LOG for VT420

_ DOL, VT420-I001, cable connector contacts may overheat

DEC 93 

NOTE:  The VT420 meets all its product specifications 
and design goals.  However, a particular component 
within the VT420 may vent.  This may be noticed by 
an odor emanating from the terminal or a whisp of 
smoke.
Note: IN ALL OCCURRENCES, THIS IS NOT A           
           SAFETY ISSUE.

FIELD EFFECTIVITY:   This part of the "I" coded 
FCO should be installed on a VT420 on a restricted ba
sis provided all the following conditions have been met:
1) VT420 products manufactured during or before         
      April 1992 are candidates.                                               
2) This FCO is for customers where the failure of the    
     VT420 may have a serious impact.
3) Each case will be handled on a case-by-case basis      
     per IPMT customer action plan.
4) The field must log an IPMT case.

PROBLEM 1: Although capacitor C621 on the VT420 
Terminal Board meets its reliabliity metric, the capaci
tor can overheat and may fail over a period of time, 
usually in a one to five year timeframe.  Symptoms 
may include:  (1) Puff of smoke and possible odor       
(2)  Cycling of power supply  

SOLUTION 1: Modify the Terminal Board (70-26536) 
by replacing capacitor C621 with the new red Wima 
capacitor.  See Below for Min Rev.

QUICK CHECK 1:   
1) Check the date on the back of the unit. 
2) Verify that the terminal board to be modified is at     
      the following revision level or below:
      70-26536-01 to 04, 10   Rev D  

      70-26536-05 to 09, 11, 13   Rev C
      70-26536-12, 14, 15, 16   Rev B 
      70-26536-17, 18    Rev A 
3) Check to see if the board already has a red Wima ca- 
     pacitor.                                

PROBLEM 2:  The contacts in the connector used on 
the yoke cable may develop high contact resistance 
which may lead to overheating.  Symptoms include:  
(1) Jittery display   (2) Discoloration of the yoke con
nector

SOLUTION 2:   Replace the yoke cable assembly with 
the new cable assembly.  If necessary, replace the 
header connector on the terminal board only if it is dis
colored or damaged.

QUICK CHECK 2:   Verify that the yoke cable con
nector and/or PCB header is discolored or damaged.

FCO KIT ORDERING:

EQ-01685-01
Qty 10 capacitor P/N 10-33421-02  
Qty 10 Green Dot P/N 36-24490-01 
Qty 10 4 wire yoke cable assy P/N 17-03950-01 
Qty 10 6 pin header connector P/N 12-27325-02, PCB 
Qty 40 in-line pins P/N 90-08091-00 
Qty 10 tie wraps P/N 90-07031-00

EQ-01685-02
Qty 50 capacitor, Qty 50 Green Dot 
Qty 50 4 wire yoke cable assy 
Qty 50 6 pin header connector for PCB
Qty 200 in-line pins	
Qty 50 tie wraps 

EQ-01685-03
Qty 100 capacitor  	                                             
Qty 100 Green Dot
Qty 100 4 wire yoke cable assy
Qty 100 6 pin header connector for PCB	
Qty 400 in-line pins	
Qty 100 tie wraps 

EQ-01685-04 
Qty 10 capacitor
Qty 10 Green Dot
Qty 10 6 wire yoke cable assy
Qty 10 6 pin header connector for PCB
Qty 60 in-line pins
Qty 10 tie wraps

EQ-01685-05
Qty 50 capacitor
Qty 50 Green Dot
Qty 50 6 wire yoke cable assy
Qty 50 6 pin header connector for PCB
Qty 300 in-line pins 
Qty 50 tie wraps

EQ-01685-06 
Qty 100 capacitor 
Qty 100 Green Dot
Qty 100 6 wire yoke cable assy
Qty 100 6 pin header connector for PCB
Qty 600 in-line pins	
Qty 100 tie wraps

(See page 5 of FCO for help in ordering the kits.)

FA-05026-01   Field Application Document (FA)