On Wed, 17 Aug 2005 09:39:36 +0100, "N Cook" put
finger to keyboard and composed:
"Franc Zabkar" wrote in message
.. .
On Tue, 16 Aug 2005 11:13:11 +0100, "N Cook" put
finger to keyboard and composed:
Jou Jye 300AP
Blown 5 amp mains fuse
There is a 1/2W resistor between the common point of the 2 x 200V mains
side
electrolytics
and one of the 2 leads , high V side of the large isolation transformer,
marked on pcb as R5 now reading 98 ohms
Overheated and probably had a brown and a red band somewhere in the
value.
Covered with some 125 degree shrink-sleeve that has charred. This was to
protect against touching other parts but this R was on end and lead
doubled
back and presumably the bang was the long lead shorted to the other
barrel
end of the R as severe tell-tale smoke 'jet-trails' at that point, no
ceramic spacer or anything .
Anyone hazard a guess what the original value might be. ?
The 2 main 2SC2625 and 200V electrolytics seem OK.
Parallel to the 4 wires of the mains side bridge rectifier is a small
sub-circuit
with (2S?) K2645 and a L8561 8 pin IC, is this all a crow-bar circuit to
knock out the mains fuse?
This smaller circuit is probably the +5VSB standby supply.
- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
It is a power factor corrector sub-circuit, would seem.
Does that mean all those millions of PC SMPS without this corrector are
getting free electicity off the generating company?
Until I got oblique lighting just right very difficult to read IC number
and it is L6561
http://www.st.com/stonline/products/...5109/l6561.htm
It looks as though the burnt resistor (2W not 1/2W as previously said) was
1K from the bands so dropping from 1K to about 100 may be the initial
problem.
At the risk of defying EU standards (which mandate PFC in new
equipment), I would remove the PFC circuitry. You will gain
reliability without increasing your power consumption. It will also
cost you nothing other than a little time.
- Franc Zabkar
--
Please remove one 's' from my address when replying by email.