23 Oct
2012
23 Oct
'12
5:25 p.m.
On Tue, 23 Oct 2012, Colin Eby wrote:
The HP9845 PSU is a complex beast, but at least it only takes in
single=phase mains...
The PSU itself is built onm 5 PCBs (or at least the one in my machine
is). 2 of them haev card edges that fit into edge connectors on the main
backplane and carry all the DC outputs. We are not concerned with those yet
There is also a 4 pin conenctor that plugs into a mating conenctor on the
chassis metalwork when the PSU is slotted it. This conenctor is wired to
a 4 way barrier strip thing on the side of the PSU casing. I asusme it';s
this that he's taling about Nothe that the order of conenctions on the
connecotr and the barrier strip are NOT the same.
The middle 2 pins of this arry the live and neutral mains, after hte
switch and fuse. The otehr 2 are shorted together by the voltaeg slector
swithc for 230V mains and are effecively a half-mains-voltaeg point using
the primary of the startup transformer as an autotransformer.This is used
ot powet the 2 120V AC cooling fans.
[Some detail on the intenrals... The startup transofrmer has apair of
120V primaries. the 4 conenctions are brought out to this barrier strip
in an illogical order :-). FOr 230V they're in series, the common
connection is the tap i just mentioned. For 115V they;re in parallel. The
main SMPUS part has the nroaml doubler/bridge rectifier circuit, the tap
of th capacitors is conencted to a suitable end of a primary widing in of
the startup transoformer]
Can you guys just sanity check something? A
colleague was scratching his
head with this, so it seemed sensible to ask.
On the mains input cable to the power supply, for 240 v external supply,
what's the test voltage we should see across each pair?
"pair"??
y'mean including neutral? ground? center tap?
"Single phase"?
"Three Phase"?
"Delta"?
"Y"?
DC?
Peak to peak?
RMS?
Single pahse, RMS, 50Hz (at least in the UK :-)).
In all cases you should see :
120V between 1 and 2 on the barrier strip. 120V between 3 and 4. Mains
(120V or 240V as apporpriate) between 2 and 3.
These questions may be stupid, but you really
didn't specify what kind of
power you are talking about.
No, but he did specify (almost) the machine. A quick look at hte
schematics of the 9845B would answer the above questions I think.
-tony