// #eevblog — 2025-09-05
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00:16:52 <electrohead> !coffee
00:16:52 * EEVBot throws screaming hot coffee at electrohead
00:47:41 Join: Kuschelpony ([email protected]) to #eevblog
04:27:53 Join: AustGuest5773 ([email protected]) to #eevblog
04:28:04 <AustGuest5773> Hello!
04:29:04 <AustGuest5773> I'm in need of some help with a LG TV PSU that keeps burning fuses.
04:33:43 <arch> AustGuest5773, what's up?
04:34:19 <arch> when does it burn fuses? randomly? on startup?
04:35:12 <AustGuest5773> The moment I put the plug in.
04:35:21 <AustGuest5773> I see the fuse light up
04:36:08 Quit: Kuschelpony ([email protected]) EOF from client
04:36:27 <arch> do you have a multimeter?
04:37:02 <arch> check the bridge rectifier using diode test
04:37:39 <arch> also check the mosfet drain-source using continuity test. most likely the psu is a flyback mode. could be a fried mosfet
04:41:22 <arch> if you have a current limited psu, you could set the psu to 30V, 0.5A current limited. pop in a new fuse, plug in the lab psu, and see which component is getting hot. you can pour some alcohol to see where it evaporates from, or you can use your lips to feel the heat rising (not recommended)
04:41:53 <AustGuest5773> The bridge rectifier D2SB60 shows ok I think. The pin configuration is + ~ ~ - .
04:42:14 <AustGuest5773> The diode test beeps on 1-3 and 2-4
04:42:33 <AustGuest5773> Not in other configuration
04:45:50 <arch> what's the voltage drop between ~ and +, ~ and -, in diode test mode
04:46:26 <arch> if you see some low value less than 0.6V, it's likely that section of the diode that's busted
04:48:45 <AustGuest5773> If I put the black lead on + and red on ~ I get 0.488V
04:49:34 <arch> now do the opposite; do they match up? in other words, you are forward biasing the diode. they should be almost identical in voltage on a good bridge diode
04:50:18 <AustGuest5773> If I put red on + and black on ~ it beeps
04:50:42 <arch> ok so that might be the short circuit there. can you desolder the bridge diode and test it out of circuit
04:53:36 <AustGuest5773> Just to cover all the bases, I tried the 2 middle pins first on pin 2 the red and pin 3 the black and I get 0.489V. If I switch the leads I get OL.
04:54:21 <arch> you cant accurately test some parts in circuit btw
04:54:28 <arch> like capacitors, or inductors
04:56:16 <arch> or like i said, easy way to find the short is to use a current limited psu and check for the hottest component
05:00:51 <AustGuest5773> One that outputs AC I presume....
05:01:35 <arch> the bridge diode actually takes ac and outputs pulsed dc
05:01:46 <arch> oh woops, misread
05:01:59 <arch> you don't need a current limited psu that outputs AC
05:02:20 <arch> you can use a DC lab psu with a low current limit set, say 0.5A, and 30V
05:02:54 <arch> because at the end of the day, the TV is using DC anyways
05:02:58 <AustGuest5773> Good. Because I really don't have the space.... XD
05:03:19 <arch> alrighty, keep us updated on your adventures
05:03:38 <AustGuest5773> I disordered the Rectifier and I get the same values as before
05:04:54 <arch> ok so that is bad. you should see ~0.6V per diode leg. ~1.2V in total drop
05:05:12 <arch> do you have a spare diode bridge, you can solder that in
05:05:14 <AustGuest5773> 1-3 beeps / 2-4 beeps and If I reverse the multimeter 0.505V
05:05:29 <AustGuest5773> *multimeter leads
05:08:54 <AustGuest5773> 1-2 and 3-4 I get 0.511V
05:09:42 <arch> ok so 1-2 and 3-4 makes sense
05:09:56 <AustGuest5773> Black on + and red ~ 0.511V and black on ~ and red on - 0.511V
05:10:26 <AustGuest5773> So the rectifier is ok?
05:10:29 <arch> ok yea so you see how they are pretty much all the same vdrop, that's good
05:11:18 <arch> check the mosfet next
05:15:21 <AustGuest5773> I have 3, 2 are flat on the board using 2 of the leads and the middle is cut using the back side as drain and 1 that is upright using all 3 leads instead
05:16:36 <AustGuest5773> 1) 1-2 2.030V / 2-3 0.447V
05:17:41 <AustGuest5773> 2) 1-2 3.297V / 2-3 0.526V
05:18:43 <AustGuest5773> 3) 1-2 1.467V / 2-3 0.356V
05:18:51 <arch> like i said, if you plug in a current limited source, you will get your problem instantly instead of all this guesswork
05:19:18 <AustGuest5773> Yeah. I think it's best
05:19:19 <arch> the hottest component will be the short
05:19:54 <rc-garage> does it do that, if the tv is not plugged in? ie, if it is only the power brick?
05:20:38 <AustGuest5773> rc-garage, yes I have it unplugged from everything.
05:20:45 <rc-garage> ok
05:22:12 <AustGuest5773> I will go buy a DC power supply that can select the Voltage and Amps.
05:22:58 <AustGuest5773> I just plug it to the AC power port and use 30v 0.5A ?
05:23:32 <arch> that's a potential 15W power dissipation. might get toasty. maybe 30V 0.1A, 3W is good
05:25:03 <arch> yes AustGuest5773 thats the idea
05:25:12 <arch> obviously make sure to solder the bridge diode back in
05:25:23 <AustGuest5773> I already did XD
05:25:37 <AustGuest5773> So I won't lose it
05:25:56 <arch> did you make sure to get the polarity right
05:26:18 <arch> or you'll blow up the input caps and mosfets
05:26:20 <AustGuest5773> Yep, I checked the board where the notch was facing
05:26:23 <arch> cool
05:27:32 <AustGuest5773> Guys/Gals thank you for the help. I will come back after I get my hands on a DC variable PSU. Time to actually get one!
05:27:43 <arch> AustGuest5773, get an analog one off ebay, used
05:27:56 <arch> dont trust the cheap chinese junk they make these days
05:28:27 <arch> i have 2 of these https://www.ebay.com/itm/146435178170
05:28:28 <EEVBot> [url] GW Instek GPC-3020 Dual Tracking Adjustable DC Power Supply | eBay | www.ebay.com
05:29:01 <AustGuest5773> Good point. I was about to ask but you beat me to it! XDD
05:29:29 <arch> the good thing about that one is you can put it in series to get a maximum of 60V 2A; or parallel, 30V 4A
05:30:05 <AustGuest5773> I was wondering why it had 2 sets of meters....\
05:30:32 <AustGuest5773> I presume the combined 60V comes from the leads on far right...
05:31:35 <arch> you just put them in series like you would a battery: black to red for 1 pair
05:32:43 <AustGuest5773> I will consult a manual before attempting it.
05:34:30 <AustGuest5773> Anyway, again thank you. I already put it on my wish list. In the first opportunity I will grab it. Have a good night or morning depending on where you are.
05:35:43 Quit: AustGuest5773 ([email protected]) Connection closed
05:38:27 * electrohead places a crown upon arch
05:42:17 * K gives arch 4 cookies
05:49:03 <rc-garage> good will instrument sends 8 stars to arch. you can use them in our online store
05:53:10 <arch> \o/
05:53:11 <EEVBot> I
05:53:11 <EEVBot> } \
05:53:55 <rc-garage> that is $-14, after tarrifs
05:59:41 <arch> rc-garage, https://i.imgflip.com/1xg6ml.jpg
06:50:00 <rc-garage> we know
07:08:09 <electrohead> https://0xznc01.pw:2600/public/2025-09-04-163713_1600x900_scrot.png
07:08:27 <electrohead> live TV from anywhere, nice.
07:15:32 <rust_collector> and that was the channel you ended up on... that is nice
07:17:33 <electrohead> yeah, lol
07:33:27 <rust_collector> some years ago, we had a tv show, just people knitting. I am not sure, it was either a day or a week of just knitting
07:44:13 <rust_collector> well, that is national tv.
07:46:23 <rust_collector> ok, it was just 12 hours.
07:47:19 <rust_collector> there is also a 7 hour train ride show, and a 134 hour boat ride, up the coast
07:48:53 <rust_collector> https://tv.nrk.no/serie/hurtigruten-minutt-for-minutt
07:48:54 <EEVBot> [url] Hurtigruten minutt for minutt - NRK TV | tv.nrk.no
07:49:15 <rust_collector> not sure if you can watch that in your foreign places or not
07:49:19 <rust_collector> I think you can
07:50:45 <rust_collector> but skip the 2 on top, that is just blah
07:57:45 Quit: broccoli ([email protected]) Quit: Ping timeout (120 seconds)
07:57:53 Join: broccoli ([email protected]) to #eevblog
11:22:11 <MrMobodies> Got a rental laptop to wipe and re-install Windows 11
11:22:31 <MrMobodies> I thought I saw "Updates are UNHAPPY" before I got the camera out and it disappeared.
11:22:38 <MrMobodies> I thought have I gone senile
11:23:27 <MrMobodies> Let's see
11:24:10 <MrMobodies> "Updates are unhappy" nope I obviously misread it as I turned my head to look.
11:24:34 <MrMobodies> I mean they don't have feelings do they.
11:25:19 <MrMobodies> If they communicate the feelings of updates they thats so damn insulting.
11:28:46 <MrMobodies> Annoyed how I typed the model number in, installed the drivers and many wouldn't not even the ATI graphics one but the Windows updater did
11:28:51 <MrMobodies> and i found this just now
11:30:23 <MrMobodies> https://i.imgur.com/UyUuLFp.jpeg
11:30:43 <MrMobodies> That wasn't there before but others were
11:31:03 <MrMobodies> and I wonder if that is why, if I saw what I thought I saw "Updates are unhappy"
11:31:37 <MrMobodies> I am doing someone a favour and the insults I get from the operating system.
11:33:19 <MrMobodies> Something like "Driver FAILED to initialize" would have been what I'd expect. Not the arrogant developers up there insulting me that the driver package has human emotions and is "upset".
11:34:21 <MrMobodies> getting my camera prepared to for another update to see if I did see that
11:36:30 <MrMobodies> Doing a bios update, tried to cancel but went through ans FAILED!
11:36:43 <MrMobodies> Absolutely P*ssed
11:36:45 <MrMobodies> oh it started
11:36:57 <MrMobodies> I thought it'd be bricked just then
11:41:25 <MrMobodies> https://i.imgur.com/ntfd6Fr.jpeg
11:42:18 <MrMobodies> Windows 98 and Web integration /Webdesktop successfully implemented 27 years down the line with the help of Chrome.
11:44:03 <MrMobodies> I remember reading at the time that that didn't live very long
11:45:05 <MrMobodies> got a problem, not my problem but from the windows update, every bootup, it tries to update the bios and fails
11:48:30 <MrMobodies> Maybe has something to do with secure boot
11:48:45 <MrMobodies> that I turned off
11:48:57 <MrMobodies> nothing in the bios about write flash permissions
11:51:16 <MrMobodies> aah since I turned on secure boot it stopped doing it
11:52:21 <MrMobodies> but so many of these "updates" and it seems ridiculous. I feel sorry for the person it is going to and that stupid out of control, "mind of it's own" touchpad with no buttons on it.
11:52:44 <MrMobodies> the tap to click I mean
11:52:50 <MrMobodies> and ht gestures
12:20:58 <rust_collector> you certainly get pissed a lot, lol
12:30:47 <MrMobodies> if something has a glitch with it I can understand, but when arrogant developers override or force their thinking onto me, designed to exclude my preferences or say, then yes.
12:31:33 <rust_collector> sure, but they do that all the time, how many times do you need to get pissed about that?
12:31:36 <MrMobodies> oh and clumsly sloppy work on something that worked for decades, the greeter screen in ubuntu and the lockout during setup
12:32:07 <MrMobodies> oh they seem different to me everytime
12:32:10 <MrMobodies> like the one above
12:32:45 <rust_collector> it is all just badly written or tested crap, that they just ship, and let you fix
12:32:58 <MrMobodies> you see I didn't think they'd communicate a failed driver or firmware in "emotions" to the user as if they were stupid, a level so low I didn't imagine they'd treat them any more stupid but no
12:33:42 <MrMobodies> I wonder how else they are going insult and degrade the user with their patronising perception of them
12:33:53 <MrMobodies> oops i mean what would they do next
12:34:03 <MrMobodies> I didn't think it'd go lower but
12:34:18 <rust_collector> dont worry, they will find a way
12:34:44 <MrMobodies> Oh yes, with this Windows 10 Enterprise LTSC 1809 buld for about another 5 years
12:35:01 <MrMobodies> but they want windows 11 on there... good luck to them
12:35:20 <MrMobodies> and it has the key in the firmware, it did activate to whatever edition it was entitled too
12:51:51 <MrMobodies> https://i.imgur.com/fQsuXpu.jpeg
12:51:57 <MrMobodies> I have an idea
12:52:26 <MrMobodies> I delete the partition and backed up the OEM partitions just incase
12:52:41 <MrMobodies> Maybe that could be why it failed the firmware update
12:52:58 <MrMobodies> what if it put it in one of those OEM partitions
12:53:05 <MrMobodies> so I am going try that now and reinstall
12:53:13 <MrMobodies> oh it's finished 7 seconds
12:53:28 <MrMobodies> quite handy Ventoy
12:53:49 <MrMobodies> this laptop apparently has no wired ethernet interface. It is a HP 255 G10
12:56:52 <MrMobodies> https://i.imgur.com/qN4r93c.jpeg
12:57:25 <MrMobodies> install windows 11 ontop and see if those partitions are retained and see what happens with this firmware issue
12:58:43 <MrMobodies> https://i.imgur.com/cLbRDOV.jpeg
12:59:25 <MrMobodies> This is nice and very convenient, a USB switching thing, with a button and an IR remote too, I have it going into a 4 way if I need to get things from other places
12:59:53 <MrMobodies> one disc for Ventoy and the other for software and disc imaging
13:00:40 <MrMobodies> "Installing Windows 11" "Your *PC* will restart several times. This might take a while..." * patronising
13:00:53 <MrMobodies> omit the information on what it was doing in the previous editions
13:01:11 <MrMobodies> aah my idea didn't work, repairing..
13:02:26 <MrMobodies> use Windows 10 one volume 3 aah working it seems
14:18:46 <MrMobodies> HP firmware updater (by American Megatrends), for a change really good.
14:19:10 <MrMobodies> allowed me to make a usb recovery bootable backup
14:19:21 <MrMobodies> "advanced users" to put them in other places
14:19:44 <MrMobodies> aah it's doing it now
14:19:48 <MrMobodies> see how it goes
14:19:57 <MrMobodies> nope it failed
14:20:37 <MrMobodies> and I did use the exact part number. I am satisified now. Not my problem I did everything I could.
14:20:49 <MrMobodies> and my tests
14:21:25 <MrMobodies> I'll tell them, if it gets bricked due to an that later on they are on their own
14:22:07 <MrMobodies> shame there is no way to directly program it from Windows
14:23:37 <MrMobodies> or maybe HP or American Megatrends don't trust Microsoft yet
14:24:02 <MrMobodies> actually no I did with one in Windows 10
14:24:15 <MrMobodies> for a Dell Optiplex last year
14:46:45 <MrMobodies> aah firmware update started and finiah with the pendrive the tool create with no prompt
14:46:56 <MrMobodies> I hope it stops nagging
14:47:22 <MrMobodies> I found the display cable is broken, if screen is at a certain angle and that laptop was only manufactuered on July last year
14:48:28 <MrMobodies> Yep worked
14:58:50 <MrMobodies> https://i.imgur.com/atHivtN.jpeg
14:59:17 <MrMobodies> Well got there in the end. Thank you very much American Megatrends, oh I use to remember their raid controllers over 20 years ago.
16:47:14 Join: watcher ([email protected]) to #eevblog
16:48:57 Quit: watcher ([email protected]) Quit: KVIrc 5.2.6 Quasar http://www.kvirc.net/
18:40:04 Quit: steve30000 ([email protected]) Quit: <Baljem> steve30: by the way, I had the most bizarre dream the other day that someone came in here and seriously flipped their shit over your quit message and why aren't the ops /doing/ something about it
18:46:16 <flyback> https://www.youtube.com/watch?v=EtIJUwkOAwM
18:46:16 <EEVBot> [YouTube] Knex 8-bit Mechanical Computer - Update 1: The ALU | 14m 37s | Channel: Shadowman39 | 116,270 views | 2025-07-12 - 19:48:03 UTC
20:05:57 Join: G-DC ([email protected]) to #eevblog
20:06:42 Quit: G-DC ([email protected]) Connection closed
21:34:17 Join: Kuschelpony ([email protected]) to #eevblog
22:30:13 <Kuschelpony> T3sl41, interested in some more info on the low-frequency impedance of telephone lines?
22:30:36 <T3sl41> sure
22:30:45 <T3sl41> i think i remembered that right, but a refresher wouldn't hurt
22:31:10 Nick: T3sl41 is now known as T3sl4
22:31:13 Quit: T3sl4 ([email protected]) Changing hosts
22:31:13 Join: T3sl4 ([email protected]) to #eevblog
22:31:28 * T3sl4 whinnys at Kuschelpony
22:31:53 <Kuschelpony> specifically related to a Stackexchange post recently
22:32:44 <Kuschelpony> at audio frequencies, a phone line is almost entirely a RC network instead of LC, so the line impedance is complex(lossy)
22:34:32 <Kuschelpony> a somewhat good approximation was a C of somewhat few µF in series with 500 to 800 Ohms
22:35:08 <Kuschelpony> for short lines, the C series-tuned with the leakage inductivity of audio transformers
22:35:14 <T3sl4> for the some km between, phone and CO, or between loading coils?
22:35:42 <Kuschelpony> that was the part about short lines
22:37:21 <Kuschelpony> long lines added loading coils, developed myMr. Pupin, that added Inductance in series with cablesegments that Xl(3kHz) < R (dc losses) so the cable could be approximated by the the lossless LC
22:38:29 <Kuschelpony> for these the characteriristic impedance was settled to 600 Ohms, just like RF has picked 50 ohms
22:40:22 <Kuschelpony> so basically you either have a long cable that was standardized to have about 600 ohms impedance, or a short cable where the impedance does not yet matter but still the convenience that telephone equipment could be arbitrarily interconnected
22:40:51 <Kuschelpony> hope that was translated well, ask if i should tr to explain more
22:42:09 <T3sl4> basically the infrastructure version of, here's a wideband amplifier for example, with some grid/base/gate and plate/collector/drain capacitance, and coupling networks thereto; or to a filter or delay line or transmission line section
22:42:33 <Kuschelpony> yes
22:42:36 <T3sl4> when things are small, we don't need to worry about the TL, but the lumped elements are still there, in whatever proportion varies between parts of the circuit
22:44:41 <Kuschelpony> yes, and the primary reason to start thinking about transmission lines at all was that the R(series) led to huge losses at lines of several ten kilometers legnth, so they started introducing L
22:44:59 <Kuschelpony> i do have lots of books about this but in german language
22:45:50 <Kuschelpony> where they explained the engineering calculations done in the 1900s for long lines, before practical amplifiers were available
23:10:51 <T3sl4> also good stuff on the BSTJ
23:39:32 Join: steve30 ([email protected]) to #eevblog
23:39:32 Mode: (by ChanOP) +o steve30
23:45:31 * electrohead places an arch waifu hat upon T3sl4
23:45:47 * T3sl4 lights his hair on fire
23:45:58 * electrohead dances
23:48:46 <Kuschelpony> also hello steve
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