<DocScrutinizer05>
alas the mein purpose of this little experiment failed: heat UPS up a bit to boil out that nasty PVC smell - but thanks to built-in fan starting as soon as PSU operates in battery-powered mode, the whole device got *cooler* instead warmer
<DocScrutinizer05>
main*
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<DocScrutinizer05>
another funny sidenote: first 19% of shown battery capacity vanished during first 60s of operation, after 120s it been down to 77% and then eventually even recovered to 78% after a few minutes
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* whitequark
just got around fixing the lab PSU
<whitequark>
the damn chinese have screwed a heatsink mounting screw to a PCB so tight it went through the mask
<whitequark>
and of course, the screw has touched a conductor at +15V, rectified right from the transformer
<DocScrutinizer05>
wow!
<whitequark>
thus putting the PSU ground at... -15V from PSU -
<whitequark>
then, I decided I should for once do all correctly and plugged in both PSU and scope into a socket with actual ground prongs.
<whitequark>
and connected scope ground to PSU -.
<whitequark>
the wire went white hot
<whitequark>
the PSU amp meter just sat there at 999
<whitequark>
who the *fuck* lays out their PCB like that
<DocScrutinizer05>
sounds almost as nasty as my universal laptop et al PSU with the PCB throughhole solder points sitting straight on a 0.2mm plastic film on top of the alu heatsink
<whitequark>
... that is in fact how I fixed it, I put mylar film between that screw and PCB :D
<whitequark>
no pointy things near though, so it should be fine
<DocScrutinizer05>
you seen the photos of mine, do you?
<whitequark>
yeah you told me
<whitequark>
I also don't understand the love of these chinese vendors for heavy transformers
<DocScrutinizer05>
ugh, this UPS makes funny noises
<whitequark>
the PSU doesn't have a single FET, non-through-hole component, two-layer PCB, or even FR-4 inside
<DocScrutinizer05>
transformers are easy to understand and build
<DocScrutinizer05>
;-)
<whitequark>
seriously, that thing would cost half as much to ship
<whitequark>
had it been built as SMPS
<DocScrutinizer05>
sure
<whitequark>
I wonder if they heard that power FETs exist
<whitequark>
It sure doens't look like so, glancing at the PCBs
<whitequark>
the LEDs have a metal mesh put at them, to emulate that VFD display feel
<whitequark>
I wonder if they revised the circuit since 1982 or not
<whitequark>
Probably not
<DocScrutinizer05>
not
<DocScrutinizer05>
it works ;-)
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<DocScrutinizer05>
and 34 monkeys got killed during R&D ;-P
<DocScrutinizer05>
I told you about that russian mini bench vice I had in 1975 or so? which had spackle filler all over it and when that came off due to an occasional hammer hit that missed the target, the steel under it had a shape like Hephaestus had hangover when smithing it
<whitequark>
lol
<whitequark>
no you didn't
<whitequark>
but that sounds about right
<whitequark>
I wouldn't be surprised if the smith literally had a hangover
<DocScrutinizer05>
http://wstaw.org/m/2015/04/17/plasma-desktopqY1954.png after 90min. note the shown load percentage which now jitters between 9% and 11%, with load unchanged. at start is was jittering between 6 and 8
<DocScrutinizer05>
voltage is also quite a bit jittery, even more on device display than on web interface
<DocScrutinizer05>
but hey, PC and monitor are happy since 90 min already
<whitequark>
eh, doubt the SMPS would care
<DocScrutinizer05>
obviously ;-)
<whitequark>
they'd work like down to 90V from 220V, a dozen or so jitter is nothing
<whitequark>
^^^ another reason everything should use SMPS, damnit
* DocScrutinizer05
picks his decent Fluke DMM
<DocScrutinizer05>
err Agilent
<DocScrutinizer05>
what I thought, a rock solid 233.[7-9]Vrms
<DocScrutinizer05>
ooh nope, 233.4 now
<DocScrutinizer05>
PSU display jerks between 229 and 231
<DocScrutinizer05>
err now it goes quite jerky even on DMM
<whitequark>
idle thought: many (but I think not all) SMPS PSUs rectify everything right away
<whitequark>
so you could basically power them with 300 VDC or so
<DocScrutinizer05>
yes, most do
<whitequark>
I've seen some truly bizarre schematics for PC ATX PSUs
<whitequark>
lemme find it
<DocScrutinizer05>
ok, one thing's for sure: I don't need the 10s periodic beep to remind me the UPS works on battery mode. The snare and hum it produces is quite enough so I won't forget about it
<DocScrutinizer05>
ouch, zilch inrush current limiting before the 470u
<DocScrutinizer05>
oops nope there's a NTC, almost missted it
<whitequark>
look above D14
<whitequark>
the fuck that trafo is doing?
<DocScrutinizer05>
wonding
<DocScrutinizer05>
wondering
<DocScrutinizer05>
maybe sort of primary feedback
<whitequark>
8-9-10-11 of TL494 is C1 E1 E2 C2 of its output transistors
<DocScrutinizer05>
actually I guess the winding next to R4 is doing a positive feedback that keept whichever transistor conducting until C7 chharged and current through C7-T3-T2 begins to decay
<whitequark>
I'm told this transformer does three things at once, it provides feedback for the overcurrent protection
<whitequark>
it allows control of the transistors on the primary side
<DocScrutinizer05>
overcurrent limiting might be another possibility, though it wouldn't work well for that
<whitequark>
and it does a sort of autogeneration with a controlled transition
<whitequark>
all at once
<DocScrutinizer05>
actually with C7 there can't be much of any overcurrent
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<whitequark>
more like secondary side overcurrent
<whitequark>
TL494 will increase duty cycle based on feedback, and at some point it'll exceed primary side specifications
<DocScrutinizer05>
nah it's a positive feedback
<whitequark>
hm
<DocScrutinizer05>
nasty: no overvoltage protection on secondary side, at all
<whitequark>
unno, maybe. my brain hurts trying to decipher this circuit, with the primary coming through the control trafo
<DocScrutinizer05>
the whole voltage stabilization is a pathetic joke
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<DocScrutinizer05>
*my* brain hurts trying to decode ZIC1 TL431C lower right
<DocScrutinizer05>
they're doing something pretty weird for 3V3 "stabilization" there
<whitequark>
haha wow
<DocScrutinizer05>
OOOH THERE is the stabilization, all to the
<DocScrutinizer05>
~ping
<infobot>
~pong
<DocScrutinizer05>
wow, UPS just cut me out without prior notice
<DocScrutinizer05>
OOOH THERE is the stabilization, all to the way to the left
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<DocScrutinizer05>
FFS
<DocScrutinizer05>
the PC went down to suspend-to-disk, but when I plugged in UPS to mains and then started up PC again, a ~90s(?) later the UPS went into shutdown mode nevertheless (some hickup from before in either the control sw on PC or the UPS itself, thinking it's still in shutdown procedure) and that of course killed off the PC cold, without suspend to disk
<DocScrutinizer05>
HAHA
<DocScrutinizer05>
[Fri 17 April 2015] [21:39:38] <DocScrutinizer05> OOOH THERE is the stabilization, all to the way to the left
<DocScrutinizer05>
is last in IRC log. I thought I sent more, but that got lost in disk cache I guess
<DocScrutinizer05>
UPS, always good for an unsolicited shutdown ;-)