17 May
2009
17 May
'09
6:28 p.m.
here is the link to the us patent office website for that number
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d…
On 5/17/09, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I've had a little more time to poke at the Apple II Europlus. It's a
240V model - reason I mention that is that the power supply is doing
strange things. If I power it up with no cards, it will do nothing for a
minute or so. Looking closely, the power light glows very dimly; the +5V
PS line is sitting at about 1V or so. After a little time, the supply
I am assuming this PSU is similar to the one shown on page 93 of the
reference manual. According to said manual, the PSU is covered by US
patent 4130862. I have no idea what that patent describes, but it might
be worth a look (although I doubt it'll be as useful as some of the old
HP patents...)
This PSU seems to have a crowbar circuit (SCR Q5, zener CR20, etc), but
amazingly it seems to be connected to the 12V output. This is, IMHO,
ridiculous. When a PSU output sits at about 1V, I often suspect that a
crowbar is triggereing, which will shut the supply down, thus enabling
the crowbar to turn off, the cycle then repeats. So what you see is an
average of the 'too high' and 'shorted' output voltages.
If the output capacitors have high ESR (a likely problem due to old age),
there will be spikes on the output, sometimes around twice the normal
output votlage. These will trip the crowbar, of course.
I have no idea why pressing reset makes any difference. I guess it is a
change in load
-tony