576/Repairs: Difference between revisions

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==Symptom: Low 5V Rail voltage + High current draw on 5V (approx. 425 mA)==
==Symptom: Low 5V Rail voltage + High current draw on 5V (approx. 425 mA)==
Replaced C759 (11KuF 15V) Shorted, showed high ESR (8 Ohms) and 8K uF capacitance.
Replaced C759 (11,000 uF 15V).
Filter Cap replacement raised the 5V Rail voltage but did not fix the issue.   
It was shorted, showed high ESR (8 Ohms) and 8,000 uF capacitance.
Voltage should be 5.0. Test readings showed 3.7V before and 3.9V after.  
Filter cap replacement raised the 5V rail voltage but did not fix the issue.   
Did not check Amp draw after, however, it is most assuredly higher that normal and still loading the supply beyond capacity.  
Voltage should be 5.0.  
Test readings showed 3.7V before and 3.9V after.  
Did not check current draw after, however, it is most assuredly higher than normal and still loading the supply beyond capacity.  
Continued troubleshooting, located high ESR (486 ohms) C789 5V Filter Cap replaced.  
Continued troubleshooting, located high ESR (486 ohms) C789 5V Filter Cap replaced.  
5 V rail came up to 4.2V.  
5 V rail came up to 4.2V.  
Disconnected Step Generator 5V @ “Q” terminal.  
Disconnected Step Generator 5V @ “Q” terminal.  
5V Rail came up to 5.04V, therefore shorted cap on Step Generator board.
5V Rail came up to 5.04V, therefore shorted cap on Step Generator board.
Located  high ESR (426 Ohm) C294 5V Filter Cap where 5V rail enters board.  
Located  high ESR (426 Ohm) C294 5V filter cap where 5V rail enters board.  
Lifted one end off the board, reconnected “Q” and 5V rail stayed at 5.04V.  
Lifted one end off the board, reconnected “Q” and 5V rail stayed at 5.04V.  
Removed Unit Right Side Frame rail, replaced  C294 on Step Generator board.  
Removed Unit Right Side Frame rail, replaced  C294 on Step Generator board.  
5V is repaired.  
5V is repaired.


==Symptom: Display trace Running off right side of CRT, cannot center==
==Symptom: Display trace Running off right side of CRT, cannot center==

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