16 May
2013
16 May
'13
8:04 a.m.
On 14/05/13 21:44, Tony Duell wrote:
How easy thst is depends on the design of the input
stage of the PSU.
PSUs that are designed to run at either mains votlage with simple-ish
conversions run the chopper circuti from 350V or so. For 110V mains,
that's got by votlage-doubling the mains, for 230V mains by simply
full-wave (bridge) rectifying it. In amny cases, 4 diodes are fitted all
the time, it's just a matter of cuttign a link to convert from 115V input
to 230V input.
This one seems to be a voltage doubler...
* AC enters via two wires soldered to the PCB
* AC enters a potted black Elmaco 511473-1K (AC line filter?). This has
L/N/E in and L/N out.
The rest of the circuit looks like this:
RT1
_____
L o---[_____]--*--|>|---------------*------------>
| | +
+--|<|-----+ --- C1
| ---
| | _____ R2
N o-----------------------|---------*------[_____]-----> To hybrid
| | +
| --- C2
| ---
| |
+---------*----------->
RT1 appears to be a MOV; there are also some resistors from C1+ to AC
neutral and the C1/C2 midpoint to some form of hybrid circuit.
Converting to a bridge rectifier would seem to involve the addition of
two diodes and the cutting of the link between AC neutral and the C1/C2
midpoint.
The question is, why does the hybrid have a midpoint reference via R2
(yel/vio/ora/gold -- 47K 5%, looks like about 0.5W to 1W rated)?
At this point, I think a power tool isolation transformer would be a
better option, but I have to replace the badly burned 18-pin 3.96mm
(0.156in) header on the power supply *and* the motherboard-side
connector first. It seems to be an ITW-Pancon Mascon connector:
http://www.iobium.com/wpc_idc_connectors.htm
http://itwpancon.com/Products/mascon_index.htm
I'm toying with replacing it with a Molex 0.156 KK, but I need to find
the crimp housings, crimps and headers. I may have to put an 8-way and a
10-way end-to-end...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/