#garfield Logs

Sep 08 2013

15:16 rue_house so last night, I took at atx power supply,
15:16 rue_house stripped off the 3.3V
15:16 rue_house stripped off the -5V and -12V
15:16 rue_house stripped off the power good circuit
15:16 rue_house stripped out the 5V section
15:17 rue_house and rewired the 12V section so that instead of bring a centertapped full bridge, it uses the 24V and charges a voltage doubler with the centerpoint of the caps grounded
15:17 rue_house it almost outputs +-24V
15:18 rue_house I took the feedback from the +24V, and the -24V is undervoltage
15:19 rue_house so I just need to reflect the -24V up so that I can get feedbak off it too
15:28 katsmeow-afk what?
15:28 katsmeow-afk <<== never got one to work properly, no matter what the directions
15:31 rue_house yea, the capacitors were a joke
15:31 rue_house 1000uF for each output
15:31 rue_house I figure, if it can handle the 250W its stamped with, I should get 5A for each of the +24 and -24V outputs
15:32 katsmeow-afk 1000u at a high freq switcher is fine, as long as they run cool and work
15:32 rue_house I gave it 4700uF (yea, a bit shy) and another 680uF after a second inductive filter
15:32 katsmeow-afk 1000u at 60/120hz sucks
15:32 rue_house for a 32A output?
15:32 katsmeow-afk 32amp!?
15:32 rue_house the 5V
15:33 rue_house pretty sure it was rated about that
15:33 katsmeow-afk no way, you'll blow it up at 35amp, try it
15:33 rue_house anyhow its all stripped out now
15:33 katsmeow-afk 35a for 1 usec
15:33 rue_house but my current issue is how to fix the feedback for the - channel
15:33 katsmeow-afk 35a for the time it takes the cap to discharage to 4.75v, then the diodes blow
15:34 rue_house I was sure that, being symettric, if I regulated the +24V, the -24V would just follow along
15:34 katsmeow-afk umm, you get only one feedback if you have onely one transformer
15:34 katsmeow-afk no
15:34 katsmeow-afk you *hope* but it seldom is
15:34 rue_house there is just one transformer
15:34 katsmeow-afk then let the -24 ride at -26. and use a 7924
15:34 rue_house I gook A-mmmmmmm-gnd-mmmmmmm-B and changed to
15:34 rue_house gnd-mmmmmmm--mmmmmmmm-A
15:35 rue_house to get 24V from the 12V coils
15:35 rue_house then did +24V-----|<-----A-------|<------ (-24V)
15:36 katsmeow-afk what's -------A------ ?
15:36 rue_house coil end
15:36 katsmeow-afk o
15:36 katsmeow-afk so you have 3amps at +/-24vdc , but the -24 isn't regulated?
15:36 rue_house then I put them thru that linked inductor (rewound) and to 4700uF caps, thru a second inductor, to 680uF and thats the outputs
15:36 rue_house yea
15:37 rue_house and the -24 really drops out, I think the feedback is fast enough to not push that stroke on the power transformer cause its not got feedack for it
15:37 katsmeow-afk i think you haveto 1) live with the unreg -24, or B) run it down to -26(ish) and use a 7924 (or make your own with an opamp and a fet)
15:37 rue_house pretty sure the -24V gets better as I load the 24V
15:38 rue_house I want 4A
15:38 rue_house I can solve this, I'm sure of it
15:38 rue_house it just needs to get feedback for the -24V
15:38 katsmeow-afk yeas, the max load on the -24 for any sorta regulation is dependant on the +24 load being slightly higher
15:38 rue_house there IS a second error amp on the controller chip, I think thats what its intended for
15:38 katsmeow-afk no, if you feedback the -24 dropping, the switcher on the primary will overvolt the +24
15:39 katsmeow-afk you can't have both
15:40 katsmeow-afk wanna know what i'd do?
15:41 katsmeow-afk make one 50v winding, make an artificial centertapped gnd for it, regulate that, and then feedback the +24 to the primary
15:41 katsmeow-afk mix that as you would like
15:42 katsmeow-afk but you get to regulate only one winding with one transformer
15:42 rue_house i disagree
15:42 rue_house I think that the prolemis partly it not bot hering with the second part of the pwm cycle
15:43 katsmeow-afk the 2nd part doesn't provide power
15:43 rue_house I bet the pwm looks like ---_---___---_---___---_---___---_-
15:43 rue_house ti still does
15:43 rue_house one polarity charges the +24, the other the -24V
15:44 katsmeow-afk no, the - is simply a identical winding as the +24 , but with the ends swapped
15:44 katsmeow-afk scope it
15:44 rue_house indeed, I"m saying its driving the transformer a-symetrrically
15:45 katsmeow-afk i know you are saying that, i disagree, and say it isn't
15:45 rue_house I'll walk it with a scope, I need to know for sure
15:45 katsmeow-afk yeas
15:45 rue_house it shouldn't be possable to asymetrically drive it.. the magnetics should saturate one way
15:45 katsmeow-afk right
15:46 rue_house I cant work on it now tho, I have piles of choares
15:46 katsmeow-afk so trigger ch 1 on the +24 drive on the secondary, and then view -24 drive on ch 2
15:46 rue_house it would be really cool if I can get it to work, I could use a +-24V supply all over the place
15:46 tsmeow-afk
15:47 katsmeow-afk i use occasional 12v batteries in series
15:47 katsmeow-afk i don't charge in series tho
15:47 katsmeow-afk 24v laptop chargers are pricey , 19v chargers are cheap
15:57 rue_house internal voltage trim pot
15:57 katsmeow-afk isn't one
15:58 rue_house 1 feedback resistor
15:58 katsmeow-afk i spent a couple minute tweaking resistors, got no changes, shurged, and put back together
15:58 rue_house you didn't find the output votlage divider?
15:58 katsmeow-afk no
15:59 katsmeow-afk found solder blobs and such tho
15:59 rue_house smt?
15:59 katsmeow-afk no
15:59 rue_house it'll be the only small resistor off the output terminal...
16:00 katsmeow-afk busy atm, not going to re-open one soon
16:00 rue_house I wonder if they use a 3 terminal voltage ref
16:00 katsmeow-afk mine aren't
16:01 rue_house did it have a ... 38.... 8 pin high side regulator chip?
16:01 katsmeow-afk the cable boxes use two tho: a 7812 in a TO-220, and a 7905 in a TO-92
16:01 katsmeow-afk i looked weeks ago, i forget now
16:02 katsmeow-afk the cable boxes regulate the +5 with the switcher, the +12 and -5 cannot be regulated the same way
16:02 rue_house I suspect they use eith 3842 or a 7 pin TO for control
16:02 katsmeow-afk there's a +50(?) unreg too, no idea why
16:02 rue_house tuning diode
16:02 katsmeow-afk prolly
16:02 rue_house :) voltage has come down on them
16:03 rue_house varicap
16:03 rue_house thats whay they are called...
16:03 tsmeow-afk is a
16:03 rue_house I couldn't remember myself :)
16:03 katsmeow-afk i just don't have the pinout or other specs on the 300 tuners i have
16:03 katsmeow-afk i'll ship you a pile of them if you can figure out how i can use them
16:04 rue_house http://www.electroniccircuitsdesign.com/sites/default/files/imagecache/main/img/TOP269EG-laptop-power-supply.JPG
16:04 rue_house hmmm
16:04 rue_house R17
16:05 katsmeow-afk whoa, way more complicated than the $7 chargers from china
16:05 rue_house lm431, thats the other number I couldn't remember
16:05 katsmeow-afk there's like 6 parts on the primary, 6 on secondary, that's it
16:05 rue_house hmm, sometimes they dont ahve a controller chip
16:05 rue_house oo
16:06 rue_house http://www.electroniq.net/files/surse/MC33374-switching-power-supply.jpg
16:06 rue_house R6
16:06 Tom_itx what's shakin?
16:07 rue_house apples
16:07 rue_house oh god, I gotta get going
16:07 katsmeow-afk rue, yeas, minus the TL431
16:07 Tom_itx u gonna b late
16:07 katsmeow-afk and a few other parts
16:08 Tom_itx don't forget what you're gonna return without this time
16:10 rue_house get new oil plug, right thread this time
16:10 rue_house take boiler to recycler
16:10 rue_house groceries
16:10 Tom_itx you strip the oil plug?
16:11 rue_house no the shop I took it to did it for me
16:11 rue_house cross threaded it
16:11 katsmeow-afk boiler died? the one with all that emt in it?
16:11 rue_house no
16:11 rue_house old boiler
16:11 katsmeow-afk o
16:12 rue_house damnit I wish people would stop telling me to keep lists
16:12 rue_house now I have damn lists everywhere
16:12 m_itx waves bye to rue as he pull out the d
16:12 Tom_itx make a list showing where your lists are
16:12 tsmeow-afk needs a list of where the lists
16:12 katsmeow-afk lol
18:23 zhanx_ just spent a month in the field i suck
18:23 zhanx_ tired
21:48 rue_house lots your edge?
21:48 rue_house I thought you were done?
22:45 tsmeow-afk tosses a capacitor-related url to rue : https://www.google.com/search?q=Halogenated+cleaning+solvents+may+permeate+the+capacitor+seal
22:45 katsmeow-afk i thought zhanx left the .mil
22:47 katsmeow-afk the charts were they tell you their caps will fail in one year are interesting
23:32 katsmeow-afk http://www.ebay.com/itm/250-6x6-A-grade-solar-cells-DIY-solar-panel-kit-with-wire-kit-12v-solar-panels-/261223707136 <<== i wish i could buy all he has of those at that price
23:36 katsmeow-afk Deep-whelm?d beneath, in vast sepulchral caves, / Oblivion dwells amid unlabell?d graves;
23:37 katsmeow-afk Balls made of Horse-dung and laid in a Room will do the same if they are new made; by which means you may whelm some things over them and keep them there.
23:38 katsmeow-afk From Middle English whelmen (�to turn over, capsize; make an arch cover; experience a reversal�), akin to Middle English whelven (�to cover over, bury; invert; bring to ruin, to move by rolling�)
23:39 katsmeow-afk so "overwhelm" means you got seriously buried, and "underwhelmed" then means you got .... what?