Thread got too loose:>>2927795

>I'm new to electronics. Where to get started?
It is an art/science of applying principles to requirements.
Find problem, learn principles, design and verify solution, build, test, post results, repeat.
Read the datasheet.

>OP source:
https://github.com/74HC14/ohmOP
bake at page 10, post in old thread

>Comprehensive list of electronics resources:
https://github.com/kitspace/awesome-electronics

>Project ideas:
https://hackaday.io
https://instructables.com/tag/type-id/category-technology/
https://adafruit.com
https://makezine.com/category/electronics/

>Books:
https://libgen.is/

>Connector identification:
connectorbook.com

>Principles (by increasing skill level):
Mims III, Getting Started in Electronics
Geier, How to Diagnose & Fix Everything Electronic
Kybett & Boysen, All New Electronics Self-Teaching Guide
Scherz & Monk, Practical Electronics for Inventors
Horowitz and Hill, The Art of Electronics

>Recommended software tools:
KiCAD 6+
Circuitmaker
Logisim Evolution

>Recommended Components/equipment:
Octopart
LCSC
eBay/AliExpress sellers, for component assortments/sample kits (caveat emptor)
Local independent electronics distributors
ladyada.net/library/procure/hobbyist.html

>Most relevant YouTube channels:
EEVblog
W2AEW
Moritz Klein

>microcontroller specific problems?
>>>/diy/mcg
>I have junk, what do?
Shitcan it
>consumer product support or PC building?
>>>/g/
>household/premises wiring?
More rules-driven than engineering, try /qtddtot/ or sparky general first
>antigravity and/or overunity?
Go away

>>2933537 (OP)
but can your SiC brick run Doop?

So I've managed to narrow down an intermittent continuity fault on the green wire. What can I do to fix it?

I was hoping to pull out the pin and draw out more wire/splice in a new section, but I don't know if its possible since it all goes into one cable. Ideally I don't want to fuck around with the other (good) wires.

>>2933161
GOOD NEWS, BOYS
Seems like I got lucky. I was trying to figure out where things go, but it's near impossible to see, at least for my untrained eyes. So I just poked around a bit near the LED header and found J503 which is connected to a shunt and the 12V pin for the fans and LEDs. There is no connection through that 0-ohm resistor/jumper. Should be safe to just bridge it with whatever, yeah?

>>2933553
Where does the other end go?

>>2933560
anon it is probable that something else wrong burnt that 0 ohm resistor. but at least you know where to look

>>2933570
There's really only the LED daughterboard as the fans connect directly and work fine separately. I should probably test that, but it has a dumb micro connector.. I only tested the LED strips directly.

>>2933576
Reflow the solder joints on the connector. Power up and touch the LED driver to find out if it's getting hot.

>>2933578
Well, good thing I asked...
When I plug in the board, 12V is shorted to ground.

>>2933585
U1 is probably dead.

>>2933587
>U1 is probably dead.


much more likely it's one the MLCC caps
they're famous for going bad
to figure it out, one uses a current limited supply at 1-2A
then check what's getting hot using a FLIR camera, or alcohol, or dust from flux, your tongue, or the inside of your foreskin

>>2933553
Connect a high-frequency oscillator / function generator output to the green wire. The higher the frequency and voltage the better, though if you can’t disconnect the other end from circuitry you’d better stick to sufficiently safe voltages (e.g. +/-0.5V). Then use a 10M oscilloscope lead referenced to the same ground as the function generator to slide alongside the wire and see where the capacitively-coupled signal drops off. You may need to tie the other side of the green wire to ground with a resistor. You may be able to do without a scope if your DMM’s AC voltage measurement can handle high frequencies, otherwise you could make a high input impedance buffer and peak detector on a breadboard with an op-amp and diode(s).

Test on a piece of wire so you know it works. Once you find where the break is, you can cut away the insulation there alone and perform a splice.
Otherwise you could consider spiral-binding a seperate green wire to the outside of the cable.

>>2933560
Bridge the 0Ω link with your DMM in amps mode, thats how I find faults.

>>2933585
Use a current-limited power supply to feed into this board. Could be a CC/CV benchtop supply, or it could be a 12V supply with a resistor in series. If you want 0.1A to go through it, you’re looking at a hundred ohms or so (2W). Then probe between the positive and negative rails throughout the PCB until you measure the lowest voltage. The lowest voltage will be across the shorted component(s). It’s possible the shorted path includes the inductor, so check that too.

>>2933623
Nah, my money is on the undersized switching converter IC too. Those things run hot, and in my experience MLCCs die open-circuit.

>>2933623
I think we might have a winner. C2 gets hot, and looks a bit wonky to boot?
>>2933663
>Bridge the 0Ω link with your DMM in amps mode, thats how I find faults
I don't have the equipment to power it outside of a pc, unfortunately.
>The lowest voltage will be across the shorted component(s).
I did try this, but maybe I'm not smart enough. C2 does measure slightly lower than its neighbors, so I think I'm going to try and tear it off tomorrow and see if it changes anything.

>>2933682
We do have a winner. C2 is a dead short.
The datasheet calls for 22µF input capacitor. The board has three input capacitors..?
Thoughts on where to go from here? I don't really have many parts lying around. Just some THT electrolytic caps.

Should I take off C3 and maybe C1 to check what they are (and turn a tarduino into a capacity meter to do so)?

>>2933803
The relevant part of the datasheet for the MP1475 is here.

>>2933803
It should work without the cap. There are 3 of them to reject more noise. Higher capacitance = low frequency, lower capacitance = high frequency.

>>2933803
So you could take one off and measure, or you could figure out the probable value based off dimensions and voltage rating. I’d guess 25V but it could be 16V, I think it’s 0805? 10uF seems likely, and even if it’s smaller there’s no downside to 10uF, because that presumably makes the entire stack of three caps something like 10+10+2.2 or so, giving you your 22uF. You could maybe cram a 22uF in there, but in 0805 it would be tough to get in an appropriate voltage rating. You can try soldering the leads of an electrolytic cap (low-ESR preferred) in there, it will probably be electrically fine because you’ve got low-impedance ceramics in parallel, but mechanically it’s pretty easy to rip of little SMD pads unless you glue the solder joints.

For testing it will probably run without that cap, and it should definitely be fine short-term with an electrolytic.

>>2933806
Yeah, it's an 0805. Seems like you can get them in 22uF at 16V though, but the 10+10+2.2 theory seems reasonable.
I do have an old scope so I suppose I could check out what the 12V looks like with some disco lights on or something?

Why would the electrolytic only be ok short term? I could hotglue things in place. I don't mind..

>>2933560
>Where does the other end go?
USB. Seems to be the normal 4 wires + a shielded layer. Idk if I'm going to be able to pull a single wire out of that.

>>2933812
Replace the whole cable or install a USB socket in the device and connect with a patch cable.

Electronics noob here, trying to bring an old automotive MD player/graphic equalizer (Sony MDX-700EQ). It came into my hands with all the wires cut off. No big deal, I thought. However I soon found out that this particular model came with an external inverter box, which I am missing. After opening up the MD player and examining it, I now know that two wires from the missing inverter go to the main board, and the remaining two - to the faceplate, which contains an LCD display and some buttons.
Google tells me that LCD displays use AC power, so it makes sense to me that it would require an inverter, as car electronics are ran off 12VDC. Am I on the right track?
In this case the LCD is driven by two LC75822E drivers. I have located its datasheet online, but Idk how to read it. The table says it requires a voltage anywhere from 3 to 6.5V, does that mean I could theoretically rig up a 12VDC to 5VAC inverter (if it's even a thing) and it should work?

Here's the datasheet for the LCD drivers: https://ksp-electronics.com/media/43160/lc75822e_w.pdf

>>2933830
Update, in my desperation I've consulted ChatGPT and it told me that this missing inverter would actually be used to power the backlight of the LCD. Sure enough, the pins of the connector on the faceplate go straight to what seems to be the LCD backlight (pic related). AI has determined the type of backlight to be EL. All this actually seems to be correct, but how do I choose what EL inverter to buy and how do I not cook the backlight? I don't know what voltage and frequency it requires :(

>>2933830
>>2933847
Looks like my vacuum fluorescent display (VFD).
https://www.instructables.com/A-Simple-Driver-for-VFD-Displays/
Give it back, Tyrone.

>>2933863
Would a VFD display use LCD drivers (pic related)?
Anyways who do I give it back to? The Japanese wrench monkey who didn't bother to unplug any wires from the car that he was taking apart and just cut them off, then proceeded to put everything he salvaged up for sale on Yahoo auctions?

>>2933830
>>2933847
>>2933875
Hello fellow MD nerd. I have one of those units. Let me take some pics for you.

>>2933887
Hi, that's awesome. Better than just taking pics, if you somehow connected an oscilloscope to the output side of the inverter (pic related), that would be incredible.

>>2933808
High ripple current can overheat higher ESR capacitors, leading to shorter lifetimes. That’s the only long-term issue with electrolytic caps in place of MLCCs.

>>2933813
Seconding this. USB B panel mount sockets are cool, C sockets are ok if it needs to be compact I guess.. It’s quite likely that the unbroken wire is just after the strain relief of the USB end itself, so not likely to be easy to repair.

>>2933847
From what I know about electroluminescent displays, they like about 1kHz and in the realm of 100V. If you have a high voltage function generator you could test that directly, if not there’s definitely ways of coupling your phone/computer’s aux-output with an audio amplifier and then probably a big audio transformer to step up the voltage.

Before you do any testing though, I’d look at at least 5 different EL LCD display module datasheets, assuming you can’t find one for your current display. If you’re lucky they’re all about the same, maybe current requirements go up by display size which is easy to factor out.

It’s also an option to disassemble the display to extract the EL backlight panel and replace it with some sort of LED diffuser, but it wouldn’t be easy.

>>2933892
I don't own a scope but I'll take pics. Often those are DC-DC up converters for VFD displays running 19v (maybe more?). But they have additional wiring pins so theirs likely some coordination and communication going on, not just dc-dc boosting.

https://filebin.net/rw0y21atw76w3gaq

Sony definitely made a service manual for this unit, but its rare to find them for units that werent sold outside Japan. Somewhere there exists a PDF with really good wiring diagrams and pinouts and probably diagnostic procedures as well. Maybe try searching on yahoo auctions japan and mercari.