Tek 2230 PSU


Thomas Drage
 

Hi All,


I was hoping for some advice on the power supply of a 2230 I'm working on.


I received the unit with mains fuse blown. Checked and found shorted rectifiers in the main bridge. I also found C904 cracked and with evidence of arcing. I found many of the LV electrolytics on both sides of the PSU having very poor ESR so I replaced pretty well all the electrolytics.


I then powered the unit up; no fuse blowing. However, the 43V supply to the inverter was not existent and C925 not charging up to power the preregulator. I did some more checking and found Q908 shorted, R909 open and C944 shorted. The FET Q9070 isn't shorted but I've not checked that it actually works.


Further, measuring resistance across C925 gives only 25ohms (having lifted R907, CR920). Is this normal or is it likely U930 is cooked too? C944 being shorted is also a bit interesting and leaves me wondering how much else of this power supply I should be suspicious of.

At present, replacing the components I know to be bad and powering up doesn't seem to to be the best idea given I don't know the cause of the issue.


http://members.iinet.net.au/~drage/other/2230PS.png http://members.iinet.net.au/~drage/other/2230PS.png <------ Schematic



http://members.iinet.net.au/~drage/other/2230PS.png

http://members.iinet.net.au/~drage/other/2230PS.png http://members.iinet.net.au/~drage/other/2230PS.png


View on members.iinet.net.au http://members.iinet.net.au/~drage/other/2230PS.png
Preview by Yahoo




Any thoughts?


Many thanks,


Thomas

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