Dell 1800FP Dark, No Power but power supply seems fine. Help!
I just repaired 3 1800FP's - all dead, no lights.
Firstly a dead 2AS01 is 95% of the problem, because some fool designer left out the protective zener diode - cheapness.
Mouser Electronics does not have this part, but lists it at 37 cents in lots of 2500, and gettable at $2.66 somewhere else.
You must also replace the two small value electrolytics near this IC, as some had an ESR of 40 where <0.5 is where it should be.
I suppose as the electro's dry out, the spikes can zap the IC. The quacks on ebay flogging 2sa01's alone, probably hope to sell you another one down the track (at a fat markup).
There are 2 'Sam Young 2200uf' electros that really should be replaced, with ESR or 2-30 ! Ideally replace ALL electros, as the others will be off - but those 4 as a minimum and using a jewelers loupe, resolder other joints on the transformer and anything that looks more dull silverish, than the rest. A 1 inch used and worn paint scraper will get the case open easy.
DANGER, CAUTION : Finally when refitting the inverter board, ensure the steel tab is over the TOP middle of the board facing away from the power socket (SO YOU CAN SEE IT) . The board sides in flat. It is possible to scew the board down with a slight bend, with the tab pressing over the pcb tracks - very , very bad!
Now all I need is for some kind soul to improve the fix by stating what the value of the missing zener should be.
PS. Just because the caps are not bulging does not mean they should be OK. Most wrecked 10 year old power supplies have better ESR's, so the electronics must be hot under the cover.
I have seen bulging caps with a GOOD ESR, and non bulging ones with an ESR of 47.
May 21, 2007 |
Dell UltraSharp 1800FP 18.1" LCD Flat...