hybridfree/eevblog-posts huggingface dataset:
Help with SMD - Page 1
Forum section: electronics / beginners

author: lavo-1
author_rank: Regular Contributor
timestamp: January 15, 2012, 10:12:00 am
content: I'm trying to fault find on a Humidity controlled extractor fan circuit that has gone faulty in my bathroom.I have tested all the through hole components and even replaced the OP amp just in case.The problem is there are six SMD components on the board that I don't recognise and to be honest haven't a clue how to test as I don't know what they are.They are I believe, SOT-23 packages as I measured their dimensions. They all have three pins/legs.They have Identity codes of:A4,L2 Z2,LN Y4.Uploaded withImageShack.usUploaded withImageShack.usUploaded withImageShack.usI'm sure you guys that work regularly with SMD components will recognise the numbers.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2012, 11:11:28 am
content: They can be quite hard to figure out, but you might get some ideas fromhttp://elektronik.googlecode.com/files/SMD_Catalog222.pdfhttp://www.s-manuals.com/smd/A component tester really helps for this, as you can easily check if its a transistor, fet or diode and narrow down the possibilities.

author: vtl
author_rank: Regular Contributor
timestamp: January 15, 2012, 11:32:57 am
content: Maybe post a picture. Component location can sometimes give you clues to what it is

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2012, 11:36:11 am
content: yeah, and the silkscreen text as well.

author: lavo-1
author_rank: Regular Contributor
timestamp: January 15, 2012, 02:08:30 pm
content: I've popped some pics in to help

author: Zero999
author_rank: Super Contributor
timestamp: January 15, 2012, 09:01:21 pm
content: I think you need to provide more information.You say it's faulty, how? What does the fan remain on continuously? Does it fail to start? Or does it randomly turn on and off?Have you tested the fan? and the humidity sensor?Your pictures are a bit too small to see and you've loaded them to imageshack which I find inconvenient - it's better to upload them here if you can and there's no reason not to if they're under the 1000KB limit.

author: lavo-1
author_rank: Regular Contributor
timestamp: January 15, 2012, 10:31:24 pm
content: Sorry if the images are too small.The Fan is running continuous once activated. I have checked the Humidity sensor with a DMM and a kettle and its fine. I have checked all the resistors (smd and through hole) and checked the two smoothing caps.I rigged up a Triac latching test using an led circuit and a 9v PSU which was fine as it latched on both + and -I just am not sure on the three legged SMD's as I am not sure what they are. I suspect that they maybe a bunch of Diodes and a FET, but I'm not 100%.
Help with SMPS PWM Feedback - Page 1
Forum section: electronics / beginners

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 24, 2012, 07:01:40 am
content: i have a circuit to study as shown in picture below. but i cannot figure out how the pwm feedback (using optocoupler) works. i probed the opto input (secondary side) indicating "always high"i have in mind as schematics below. i cannot find in the net similarly simplicity circuit, mostly they are even more complicated. to avoid blowing things up (limited parts supply) i need an advice on pwm feedback control. i've tried feeding fixed PWM in test circuit below (using LA battery), it just pulled the damned circuit low, ie short circuit through the transformer. i just find any short in transformer's input connection (there are 4 pin in primary, 2 pin out of secondary) in hope there is a coil inside and use the pins as the input from the circuit, did i do anything wrong? any link to circuit example relevant to the schematics below? SOS, thanks.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 24, 2012, 02:11:10 pm
content: Tr is transformer, sorry if i used nonstandard notation. and maybe i misunderstood between varistor and Y-cap, i'll read again. the pwm controller chip is 3843CM black soic smd 7oclock from board center in the picture above. thanks for the link BAW, i'll need time for that, my net is slow. i've found another circuit in the net (fromhttp://www.poweresim.com), somewhat similar, but different. but then, i'll need time to understand the feedback mechanism.
Help with Solar Design for Circuit - Page 1
Forum section: electronics / beginners

author: Dicko
author_rank: Contributor
timestamp: February 01, 2023, 06:56:53 pm
content: Hello folks,I have a battery powered application that will sit outside. The battery is a 3.7V LiPo, 3700mAh with a discharge current of about 128uA. I want to use a solar panel to recharge the battery in sunny conditions. I was thinking of using this panel, and LiPo charger. Just wondering how to connect them.I was thinking of connecting the battery to the battery I input. Then Vout to a pair a wires connected to a jst connector which will go into the jst port of the Arduino. The Vin I will connect to a solar panel.https://cpc.farnell.com/seeed-studio/313070004/solar-panel-55x70-0-5w/dp/MK00380?mckv=s_dm%7Cpcrid%7C224646539664%7Ckword%7C%7Cmatch%7C%7Cplid%7C%7Cslid%7C%7Cproduct%7CMK00380%7Cpgrid%7C49734053271%7Cptaid%7Cpla-1212017578951%7C&CMP=KNC-GUK-CPC-SHOPPING-945765023-49734053271-MK00380&s_kwcid=AL!5616!3!224646539664!!!network%7D!1212017578951!&gclid=CjwKCAiAuOieBhAIEiwAgjCvcqJiOXxSJGhAlo1UY4-MR3G8UcDlMZAzP-dM2aMXGJ2bOGe7YSHDoBoC2ygQAvD_BwEhttps://uk.farnell.com/dfrobot/dfr0264/solar-lipo-charger-3-7v/dp/3769969?ost=3769969The device it is powering is the Arduino WAN 1310https://docs.arduino.cc/hardware/mkr-wan-1310

author: m k
author_rank: Super Contributor
timestamp: February 05, 2023, 03:45:05 pm
content: Panel -> charger -> load.It's that simple.Your charger is also charging much more, so minimal extra load is not a problem.
Help with sons beginner robot science fair project. - Page 1
Forum section: electronics / beginners

author: dennisyuki
author_rank: Contributor
timestamp: December 06, 2016, 12:32:36 pm
content: My son and I built a basic obstacle avoidance machine. No micros. Just a simple H bridge using some switches. This is the plan we started with but I upgraded the motor that included a gear box and wheels.http://www.robotshop.com/blog/en/how-to-build-a-simple-robot-beetle-robot-4085wheels and gear boxhttps://www.amazon.com/DIYmall-Uniaxial-Geared-Magnetic-Gearbox/dp/B012FYMW54/ref=sr_1_6?ie=UTF8&qid=1481027288&sr=8-6&keywords=robot+motor+gear+wheelI changed the battery pack to 6v using 4 AA batteries. Everything is working fine except the batteries only last about 1 min. Is there a way to make the robot have a longer run time? Thanks in advance.

author: Andy Watson
author_rank: Super Contributor
timestamp: December 06, 2016, 12:48:37 pm
content: Any chance of a photo (or two) showing how you've wired it?

author: Zero999
author_rank: Super Contributor
timestamp: December 06, 2016, 01:12:23 pm
content: The batteries should last longer than that, with the components you've linked to. Either you've used flat batteries, made a wiring error which shorts out the batteries or motor/gearbox is faulty.Did the batteries, wiring or get hot? If the answer is no, then you've used flat or fake batteries. If the answer is yes, then there's something wrong with the wiring, mechanical assembly or motor.

author: dennisyuki
author_rank: Contributor
timestamp: December 06, 2016, 01:20:12 pm
content: Quote from: Andy Watson on December 06, 2016, 12:48:37 pmIm at work. so I will take some tonight.

author: dennisyuki
author_rank: Contributor
timestamp: December 06, 2016, 01:23:15 pm
content: Quote from: Hero999 on December 06, 2016, 01:12:23 pmI changed the batteries with fresh alkaline and did the same. I did not feel the temp. I will check it tonight.

author: Rick Law
author_rank: Super Contributor
timestamp: December 06, 2016, 07:16:01 pm
content: Just a suggestion...If it is yourson's"science fair" project, may it be better to just give him advice and choices? Let him have the ownership of making the choices, the building, the "figuring things out", and he may learn more and feel more ownership to the project.
Help with sourcing mov's? - Page 1
Forum section: electronics / beginners

author: youshouldatappd
author_rank: Newbie
timestamp: May 02, 2014, 08:08:10 am
content: Firstly, hi guys my name is Grant and im new to the forum.Due to an incident at work, I have had my fluke 1587 damaged. The component that now needs replacing is a k575 mov, which I have been unsuccessfully able to source. The only mov's that I am able to source are 10mm wide, whilst the mov's that I am after are about 4-5 mm . Attached is a picture of the damaged mov i'm attempting to source. Any assistance is greatly appreciated.Sent from my GT-I9505 using Tapatalk

author: SeanB
author_rank: Super Contributor
timestamp: May 02, 2014, 11:54:14 am
content: If the 10mm one physically fits in the space use it.
Help with specification of Tenma 72-8695A DC PSU - Page 1
Forum section: electronics / beginners

author: RocketMan
author_rank: Newbie
timestamp: September 28, 2021, 07:08:03 am
content: Good morning everyone, I would really appreciate some help in understanding how to work out the specification of a Tenma 72-8695A DC PSU. I have looked up other Tenma DC PSU's and they all give a setup accuracy like 0.5% + 10mV for voltage and 0.5% + 10mA for current but as you can see from the datasheet I have attached the 72-8695A is very different.I am relatively new to all this and any help would be greatly appreciated.Thank you

author: ledtester
author_rank: Super Contributor
timestamp: September 29, 2021, 09:07:50 am
content: Can you give links to some of the other Tenma datasheets you have looked at?

author: RocketMan
author_rank: Newbie
timestamp: September 29, 2021, 09:12:16 am
content: Hi Ledtester, I can only find this onehttps://www.farnell.com/datasheets/2610492.pdfand its the same details as what's on the user manual. I have even emailed Tenma but still awaiting a reply. Any help you could offer would be much appreciated.

author: wraper
author_rank: Unknown
timestamp: September 29, 2021, 09:16:00 am
content: BTW this is just rebranded and more expensive UNI-T UTP3704S.

author: RocketMan
author_rank: Newbie
timestamp: September 29, 2021, 09:28:04 am
content: Hi Wraper, that is very interesting and a great spot. My only issue is this has the same details for spec as the Tenma so I'm still in the dark

author: wraper
author_rank: Unknown
timestamp: September 29, 2021, 09:33:49 am
content: I guess "mutual effect" means channels affecting each other, crosstalk of sorts. Dunno what "overload effect" is supposed to mean, looks like Chinglish. Also they don't even have separate specs for 5V channel which should be different from the rest.

author: RocketMan
author_rank: Newbie
timestamp: September 29, 2021, 09:37:02 am
content: I know, it's rubbish isn't it. I'm glad I'm not the only one who thinks it lolBasically I been given this at work and asked to calibrate it. I'm going to tell them to send it back 🤣Thank you both for your input on this, really appreciate it.This seems to be a good active forum 👍
Help with strange SMD device ID - Page 1
Forum section: electronics / beginners

author: AE7OO
author_rank: Regular Contributor
timestamp: May 22, 2019, 02:06:43 pm
content: Greetings,I was doing some part scrounging from some old hard drives I had and ran across the devices in the PulledChip and BoardedChip pictures. I'm not really sure what to make of them. They are fairly large(MMref picture has a mm scale); Looks like they are about 4mm long. The first three pictures show the device in question(The 4th one has markings identical with the BoardedChip). The 4th picture shows the circuit one of them came out of.I've tried looking it up under just about every combination of markings I could imagine, no luck there. And metering it told me nothing, which considering I really only have low end meters(I tried both with a Multimeter(Centech 61593) and LCR meter(HoldPeak HP-4070L)) does not really mean much.I want to half way say crystal because of the guard circuit (and the above metering) as seen in the Circuit picture, but there are other devices that require the same treatment.Plus considering the following info, I would have to say no:- in all cases they were located away from any device- there were already crystals/osc in use(an example is in the WithOsc picture)- I've never seen anything like it in 30+ years. I will admit however this is the first time I really paid attention to devices located on HD boards.- In all cases they did not have a board reference of either X or Y. E2, SK1, V and VR2 were how they were referred to(I could not find E1 or VR1); So I'm thinking they are not very common as there is no standard reference.Maybe a voltage reference?(Also can anyone help me interpret the resister in the last picture with the blue marking. I don't know if I should treat it as 205 or 2.5(I've already run across a resister marked with 1.0 so it might be 2.5))4 out of the 5 logic boards I pulled had this device.

author: Buriedcode
author_rank: Super Contributor
timestamp: May 22, 2019, 02:10:23 pm
content: I believe the silver/white device to be a shock sensor. These are used to detect falling, or sudden shocks so the drive can retract the heads to a safer place to reduce potential damage from the sudden shock when it hits the floor.https://www.murata.com/en-eu/products/sensor/shockhttps://en.wikipedia.org/wiki/Active_hard-drive_protection

author: AE7OO
author_rank: Regular Contributor
timestamp: May 22, 2019, 05:37:46 pm
content: Thank you!!That tells me why I've never seen one before! I thought my memory was going.I've worked on various types of RF equipment, computers, and POS scanning systems. None of which had a shock sensor like this...

author: Buriedcode
author_rank: Super Contributor
timestamp: May 22, 2019, 07:54:47 pm
content: Yeah they're pretty nifty. I believe it is to stop the heads crashing into the platters, so whilst the fall/drop/shock/hit may permanently damage the heads - the platter(s) remain intact so techs can replace the heads and extract the data. So damage limitation, rather than prevention.
Help with testing an RF Transformer - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: February 08, 2023, 12:38:58 am
content: I have a TSO-4-2 RF Transformer I am trying to test. I pulled it from the board and used a continuity tester to see if short exist as I’m not sure of any other way to test it. I attached a datasheet, schematic of it in circuit and pic af the actual transformer.I’m seeing all the pins connected except pins 3,4 & 5 that seem to be floating and not connected to anything.

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 08, 2023, 01:28:12 am
content: Using an ohmmeter isn't going to tell you much beyond that you don't have a open winding. Hopefully your continuity tester didn't put much more than 30ma through the windings or you may have damaged it.According tothe datasheetit looks like a 1:4 RF transformer.If you had 2 of them, you could put them back to back and test them with a standard 50 ohm RF sig gen and 50 ohm power meter @ 10Mhz. Or a VNA if you had one of those. (Split the insertion losses in half because there's two of them)If you just have one transformer, since it's a1:41:2 turns ratio with a primary impedance of 50 ohms. that means the secondary should be800 ohms200 ohms (RF impedancenotDC resistance). So you could load the secondary with an800 ohm200 ohm resistor, generate an RF signal, measure the RF voltage (with an RF voltmeter) on the primary and secondary sides to see the1:41:2 ratio to get a basic go/no-go test. Or use a VNA to check SWR on the 50 ohm side, and add/remove the800200 load on the secondary to verify functionality.NOTE: Edited to correct my impedance ratio mistake as pointed out by Bud...

author: srb1954
author_rank: Super Contributor
timestamp: February 08, 2023, 04:58:40 am
content: If you have an LCR meter you could measure the inductance of each side of the transformer, with the other side OC. You will get better results with an LCR meter having a test frequency of 10kHz or higher - a test frequency less than that will yield poorer accuracy measurements considering the relatively small inductances expected in such a transformer.You will probably see inductances in the range 10-100uH with the secondary having approximately 4x the inductance of the primary.

author: Bud
author_rank: Super Contributor
timestamp: February 08, 2023, 07:11:29 am
content: The datasheet specifies 1:4 impedance ratio, not turns ratio. Therefore the primary is 50 Ohm, secondary is 200 Ohm RF impedance. Turns ratio is a square root of impedance ratio, so turns ratio of this transforner is 1:2.

author: radiolistener
author_rank: Super Contributor
timestamp: February 08, 2023, 12:25:15 pm
content: if 1 to 6 and 2 to 6 have low resistance then it is ok

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 08, 2023, 04:21:58 pm
content: Quote from: Bud on February 08, 2023, 07:11:29 amOoops! Not sure how I missed thesymbol, but I see it now.
Help with TPS61023 - Page 1
Forum section: electronics / beginners

author: 404notfound
author_rank: Newbie
timestamp: February 17, 2025, 12:38:12 pm
content: Hi all,I am having some issues with a TPS61023 from Texas Instrument.I am using WEBENCH Power Designer from TI to design my power supply. (Linkhttps://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=596F065B4F17B3A1to "my" design).In theory, I can work from ~1.5V to 3.6V to boost voltage up to 3.3V.However, below 2.5V, the IC "shuts off"...I checked the feedback pin, it ranged from 0.3V bellow 2.5V input to 0.4;0.6V with input voltage above 3V.This "power supply" powered an ESP 12F. You can check my PCB design here:https://pro.easyeda.com/editor#id=a962e7a75ae043559788beba2e07cb2eIs there an obvious problem?Thanks !

author: xvr
author_rank: Frequent Contributor
timestamp: February 18, 2025, 11:29:52 am
content: Output capacitor placed too far from IC. Datasheet says:QuoteAlso input bulk capacitor recomended:Quote

author: CaptDon
author_rank: Super Contributor
timestamp: February 18, 2025, 01:27:53 pm
content: Operates from .5v to 5.5v and the input must be well regulated?That seems like a stupid spec for a buck / boost converter. If by well regulated they mean lots of bulk capacitance it should state that parameter, which I think they do. The operating input voltage varies over a decade, I wouldn't call that 'well regulated'.
Help with transfer function and circuit design - Page 1
Forum section: electronics / beginners

author: pas2007
author_rank: Newbie
timestamp: September 25, 2015, 12:47:48 pm
content: Hello i am new to this forum.I want to design a circuit with 5 opamps that implements this function transfer: G(s)=10/[(s+1) (s+5)]it must be like this:https://www.dropbox.com/s/opsaabvrvighvqm/opamp.JPG?dl=0i don't know much about this type of project but any help would be great.Thank you

author: LvW
author_rank: Frequent Contributor
timestamp: September 27, 2015, 09:46:12 am
content: Quote from: pas2007 on September 25, 2015, 12:47:48 pmIt is surprising that you are going to use 5 opamps for such a simple circuit.It is a second order lowpass that can be realized by a cascade of two opamp circuits as shown in the link.As an alternative, you can use two simple first order RC stages and a separate gain stage.Together with buffer decoupling you need three opamps.
Help with transfer function of an active filter - Page 1
Forum section: electronics / beginners

author: Johan Loubser
author_rank: Newbie
timestamp: October 09, 2019, 07:05:40 pm
content: Hi, I am struggling to find the transfer function of the circuit (https://www.dropbox.com/s/rfmu88nxkairjbm/Capture.PNG?dl=0)If someone can help or provide a method of finding the transfer function it would be greatly appreciatedThe end goal is to find the amplitude and phase response of the filter.Thank you in advance.

author: L_Euler
author_rank: Regular Contributor
timestamp: October 09, 2019, 07:25:27 pm
content: To start with V- = V+ = Vo. Also, might try Y-Delta transform on the two passive networks.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: October 10, 2019, 06:56:47 am
content: First number the nodes as follows:The node at the junction of C1, C2 as 1 and name the voltage there as V1The node at the junction of R1, R3 as 2 and name the voltage there as V2The node at the junction of +ve input of op-amp as 3 and name the voltage there as V3Then write KCL equations for those three nodes. You will have 3 equations in 3 unknowns, V1, V2, V3.Note that the output voltage is equal to V3.Next, solve those equations by:re-arranging the first equation for V1 and substituting this expression into the other two equations. This gives you two equations for V2 and V3.Next:re-arrange one of those two equations for V2 and substitute this expression for V2 into the other.Now you have one equation for V3 alone in terms of the component values and the input voltage.Next, re-arrange the expression you have for V3 in the form V3/Vin = function(all components).Lastly try to arrange the function into some canonical form of a ratio of two polynomials.You're done.
Help with transfering data from circuit board memory - Page 1
Forum section: electronics / beginners

author: silviasol
author_rank: Regular Contributor
timestamp: April 23, 2018, 09:27:12 pm
content: I am trying, hoping, to find a way to transfer data from one circuit board to another. It is a ps vita(portable playstation console). There is homebrew stuff like installing original doom on it if you have firmware version 3.6 or below. So I have one board with 3.6 firmware. Is there any way of pulling all memory from one chip and transfering it to another. I have bga station, hakko board heater and hot air with wand holder/arm. I have done bga reball all that stuff so am completely capable, for the most part... Here are some pictures of the board. I know there are cell phone stuff like pull the memory chip off then reprogram it with special tools. Would this be possible? Here are pics of the board and it's chips. I came to you guys because you seem to know everything based on my other questions in the pasthttps://imgur.com/a/xmjvXc6

author: abraxa
author_rank: Frequent Contributor
timestamp: April 24, 2018, 07:34:18 pm
content: You're asking a very specific question but maybe there's another way to achieve what you want. However, you didn't say what it is that you want in the first place. I suggest you broaden the scope of the question and let us know

author: amyk
author_rank: Super Contributor
timestamp: April 25, 2018, 01:37:37 am
content: I haven't looked in detail at this particular one but a lot of consoles use DRM so even a full flash dump might not work correctly --- there's layers of unique keys and encryption involved.

author: silviasol
author_rank: Regular Contributor
timestamp: April 25, 2018, 01:34:06 pm
content: So probably not worth looking into then? I guess I should feel lucky I have one with the correct firmware, they are really hard to find these days.

author: @rt
author_rank: Super Contributor
timestamp: April 25, 2018, 01:56:18 pm
content: From the second or so revision PSP there were different PCB revisions that would behave differently with the same software.The earliest anomaly I remember was the TA-082 hardware which by the enclosure, was not distinguishable from other units,but if you downgraded it below 2.5 firmware, it would brick (before even the first unbricking with battery & MS came about).I wrote a pretty famous at the time program called X-Flash which customised wallpapers, text, audio samples, and other stuff,before Sony included any mechanism to do the same in their XMB menu. It wasn’t till about 2.0 you could customise much.TA-082 hardware could not run that program, and I ended up having to detect it and exit the program just in case.That, and as already mentioned, your NAND will have data pertaining to some other serialised components on the board.
Help with transistors - Page 1
Forum section: electronics / beginners

author: Alaezae
author_rank: Contributor
timestamp: October 17, 2020, 08:07:49 pm
content: Hello,I've been reading through the transistor section of the art of electronics and it's great, I certainly learned a lot. The problem is that I want to design a common emitter amplifier to build a Colpitts oscillator, but I'm very confused just based on the book. Let me explainI have basically no information on what I'm building (at least compared to what I'm given in practice problems). I have a Vcc (+5V), I can figure out the gain from the capacitor ratio in the resonant circuit, and I know the type of transistor I'm going to use (2N2222, I'm sure someone will tell me that's a bad choice for one reason or another but it's all I have). Most of the practice problems I've done online either start with a completed amplifier and then have you figure out the load line and Q-point, or they give you the Q-point or output impedance and load or something. I've got all that figured out, but when I actually want to build one up I don't have any parameters.I turned to the internet for a solution, but the range of answers online for practical advice on picking parameters is very wide. Most places I look, they say find the Q-point based on the load line, but to figure out the load line I need to bias the transistor, and to bias the transistor I need the Q-point! I found a site that said the collector current should be around 12% of I(max) for the transistor, which is weird I don't know where that number came from.I guess to summarize, my question is how do I figure out the design parameters of the transistor based on what I have (Vcc and gain)?Thanks

author: bob91343
author_rank: Super Contributor
timestamp: October 17, 2020, 09:57:09 pm
content: Well first decide on an operating point. Say 10 mA as a start. Then select an emitter resistor to give that current with grounded base and maybe 12 V on the collector.Then add the tank circuit and it should work. The impedance of the tank is roughly square root of L/C so there is your starting point.I always prefer analog design to computer aided because the latter seems always to have traps for the unwary as well as no reluctance in presenting you with a ridiculous set of component values.A good idea is to look at existing designs to gain some perspective.
Help with troubleshooting electronic components - Page 1
Forum section: electronics / beginners

author: Szewczykm
author_rank: Regular Contributor
timestamp: December 05, 2012, 04:37:41 pm
content: I’m an electronics and pinball hobbyist. Right now I am trying to troubleshoot a problem with a 20 year old sound board. I’m getting a hum from one speaker. I’ve swapped in a known good sound board and the hum does not exist. I’m reasonably certain now that there isn’t a problem with an interconnect, bad ground connection, or thing like that.Working on 20+ year old pinball machines, one of the first things we do is to replace all of the electrolytic caps whether they need it or not.I’ve done that and the hum has remained. What I’m wondering is how you might approach troubleshooting a board like this. A mix of components. Do ceramic caps fail like electrolitics do? Is that a likely place to start or are there more likely components to fail?I’ve been looking at ESR meters to help make the job of cap testing easier, but I’m reading that an ESR meter is to be used for caps 1uf or bigger. Is there a quick way to test the oodles of .1uf, 2200pf, etc.. ceramic caps?I troubleshoot I.T. stuff all day. Networks, databases, servers and the like. Troubleshooting involves decision trees and to be quick about it, the top of the tree is normally “What is most likely the problem” , “check the leading indicators that give you better direction”, and “given no indication of what the problem might be, start with the easiest/fastest things to check and work your way down to the hardest/slowest”.Here is the schematic for the sound board. The channel with hum is Speaker 1. The output can be found on the upper right side of the schematic, CN1-1 and CN1-2. If it were you trying to find the source of hum, what would you check first, second, third, and how would you check each thing?Page 15http://mirror2.ipdb.org/files/2358/Data_East_1992_Star_Wars_Schematic_Diagrams_English_Manual_pages_46_69.pdf

author: SeanB
author_rank: Super Contributor
timestamp: December 05, 2012, 06:20:20 pm
content: If the hum is only on speaker 1, and not 2 or 3, then it is down to U31 and everything after and including R19. Likely one of C64,65,66 is open circuit, easiest to change them out. If you have changed C61,62,67 then the only thing left is U32. Have you measured the voltage at the speaker terminals with the speaker not connected, if they are very different ( more than 1V different) then either there is a dry joint on the IC or it is faulty. Reflow the pins and try again, otherwise replace it.

author: PhynixViking
author_rank: Regular Contributor
timestamp: December 06, 2012, 09:07:42 am
content: That was really odd... I posted a reply to another topic and it ended up here. (ignore this i guess...)

author: ptricks
author_rank: Frequent Contributor
timestamp: December 06, 2012, 12:29:38 pm
content: Easiest way to find it is use a audio test probe. You can make one with a 1uf cap and a 10K resistor connected in series to an audio amp. The audio amp should be battery powered for best results. Start at the inputs to the audio stage and follow till you find the hum.
Help with understanding my bench power supply. - Page 1
Forum section: electronics / beginners

author: bwat
author_rank: Frequent Contributor
timestamp: June 18, 2014, 08:32:57 pm
content: Hello,I'm going through a process of relearning all the electronics I was taught at school many moons ago. To do this I'm working my way through a book and today's topic is Thevenin's theorem. I decided to create a circuit similar to the one in the book but using voltage sources and resistors that I had available so I could verify the results with measurements. A circuit diagramme is attached.I used my bench power supply instead of batteries. Channel 1 was set to 5V and channel 2 to 10V. When I connected the circuit, channel 1 then showed 9V on the power supply and channel 2 was unchanged at 10V. This change in voltage was verified with my DMM and the voltage drops were measured to 1V so this is correct (10 - 9 = 1). When I measured the open circuit current (A-B), channel 1 dropped to 5V again.My question is this: why did channel 1 change to 9V? The model in my head says that there should be 30mA in the loop ((10-5)/166) but I'm getting 6.1mA. Its almost as if channel 1 was a 1473 ohm resistor (10/0.0061 - 166).I'm lost and I'm grateful for any help you can offer. Thanks in advance.

author: edpalmer42
author_rank: Super Contributor
timestamp: June 18, 2014, 09:11:41 pm
content: Most power supplies are designed to act as a current source, but not a current sink. In your example, the 5V supply saw 10V coming at it. It has no way to sink current to pull the voltage back down to 5V so the voltage rises. The final value of the voltage depends on the internal details of the power supply's design and the external circuit.To get your example to work as intended, either replace the 5V supply with batteries ( four Nimh cells would get you ~ 4V8), or put a 5V1 zener across the 5V supply.Ed

author: bwat
author_rank: Frequent Contributor
timestamp: June 20, 2014, 06:51:42 pm
content: I tried your Zener diode suggestion and it worked a treat. Many thanks!

author: edpalmer42
author_rank: Super Contributor
timestamp: June 20, 2014, 11:00:08 pm
content: Glad I could help. Thanks for letting me know. It's always nice to hear that an idea worked out!Ed
Help with unknown LCD 84*8 1 Line dot matrix - Page 1
Forum section: electronics / beginners

author: mj21
author_rank: Regular Contributor
timestamp: July 01, 2020, 09:36:19 am
content: hi allhas anyone ever come across these small one line Dot Matrix LCDs? I cant find any datasheet for them , seem to be some sort of OEM for some R&D company. they come in 2 different part numbers. but both the same. HC-84*8-6674 OR SCM211A .i am trying to see if i can interface them with Arduino but having no luck.any help is highly appreciated.
help with usb A to type c and MCU - Page 1
Forum section: electronics / beginners

author: dorimon1000
author_rank: Newbie
timestamp: May 21, 2024, 06:16:46 pm
content: hi everyone! im designing a board which will include RT1170 family MCU and im willing to place a Type C connector for ease of connectivity.the thing is im really confused on how should i connect it if i want to burn image to the MCU with that USB port..from my understanding , the PC is the host which will be connected to the type C via a cable TYPE A to TYPE C plugs.the thing is , i dont know if simply leaving the CC pins will do the job, (and of course shorting the D+ pair and the D- pair.i want to be able simply give power to the USB1 BUS and to be able to upload the image. meaning the MCU will be the device, the pc will be the HOST.how do i achieve that?thanks!!

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2024, 07:45:11 pm
content: For it to be a device you need to properly connect D+/D- (not shorting them). And you need to connect 5.1 kOhm resistors to the ground from the CCx pins (one per pin).You also need to check if there is some bootloader that can talk over USB on that device. And if not, you will have to find or make one. And if there is one, you need to read its exact requirements. Bootloader may put additional requirements on the crystal frequency, for example.

author: dorimon1000
author_rank: Newbie
timestamp: May 21, 2024, 07:54:55 pm
content: D+ D- arent shorted , usb C has 2 pins D+ and 2 pins D- .. so the D- are shorted together and the D+ pair are together (thats incase the type c will be plugged in other direction)what i dont understand is why put 5.1k resistors to gnd on the ccX pins , since USB A doesnt even have these pins , only the type C part has.. and my mcu has nothing to do with the CCx pins..

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2024, 08:04:31 pm
content: Well, yes, you need to connect D+ and D- pairs.You don't need CCx pins if you don't plan on using USB-C to USB-C cables. But if you actually want to be compliant to the standard and work in all cases, then you need them.

author: dorimon1000
author_rank: Newbie
timestamp: May 22, 2024, 06:13:22 pm
content: but will that allow me connect host to my MCU? i dont want to connect a device such as a keyboard , just to be able to program the MCU from PC

author: ataradov
author_rank: Super Contributor
timestamp: May 22, 2024, 06:43:39 pm
content: Yes it will as long as there is a USB bootloader running. It won't just work on its own if there is no corresponding software running. You need to check if there is a bootloader in the ROM in that device. If not, then you will have to use the regular programming interface once to place the bootloader. After that bootloader will be able to program the flash over USB.
Help with USB power switching - Page 1
Forum section: electronics / beginners

author: HodgePodge
author_rank: Newbie
timestamp: April 04, 2014, 01:57:21 am
content: Hello all!I am building a small portable music rig to carry around, to run off battery power when I'm on the go, and be able to plug in into a USB socket at home.Its basically an iPOD, an amp and a DAC and all of them use 5V so that's not a problem.For aesthetic reasons I am powering them using 4xAA batteries, and I've noticed that rechargables would give me 4.8V and alkalines give me almost 6.0V which I need to regulate to ~5V. Furthermore, if I add the ability to use USB power, I would need some diodes to keep the USB power from trying to charge the batteries. So with schottky diodes, I would additionally have to factor in forward voltage drops...Any help would be greatly appreciated.Thanks!

author: mariush
author_rank: Super Contributor
timestamp: April 04, 2014, 05:24:30 am
content: See an IC like this one :http://www.digikey.com/product-detail/en/TPS2115APWR/296-16940-1-ND/652794Page 16, Figure 14 shows an example circuit exactly for the design you want.You can use a fixed 5v switching regulator to get 5v out of those batteries, see for example MIC4575 :http://www.digikey.com/product-detail/en/MIC4575-5.0WU/576-1216-ND/771685Or LT1376.. it's not cheap but it's in DIP package :http://www.digikey.com/product-detail/en/LT1376CN8-5%23PBF/LT1376CN8-5%23PBF-ND/891357Have a look at others in the same category (source selector / switch):http://www.digikey.com/product-search/en?FV=fff40027%2Cfff80320&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&quantity=10&ptm=0&fid=0&pageSize=25
Help with USB sound card oscilloscope - Page 1
Forum section: electronics / beginners

author: sevenofnine33
author_rank: Contributor
timestamp: April 19, 2018, 06:41:43 pm
content: Hello, I just bought a USB sound card and was hoping to make it into an oscilloscope. The problem is I'm not sure how I'm supposed to do it. Projects I found online were not clear to me, can anybody help?http://www.instructables.com/id/USB-Oscilloscope-with-Signal-generator/Is this a good project?

author: abraxa
author_rank: Frequent Contributor
timestamp: April 19, 2018, 08:05:07 pm
content: Question is: what do you want to examine?Unfortunately, using a sound card to look at signals is difficult and can be quite confusing because the signal is heavily distorted before it is captured by the A/D converter.I'm not telling you that it can't be done, only that you may be better off investing your time and money in something more worthwhile.
Help with Waveguide Transitions: Continuity, Amplitude Equations, and Fourier Ex - Page 1
Forum section: electronics / beginners

author: Ahiya
author_rank: Newbie
timestamp: March 23, 2025, 01:58:24 pm
content: Hello everyone,I’m working on an assignment involving a rectangular waveguide attenuator (composed of three sections) where the middle section is wide enough that the main TE10 mode experiences significant attenuation. I understand how to calculate the attenuation itself, but I’m struggling with the exact procedure to analyze the transitions between the different waveguide sections.I’ve attached both the assignment and the explanatory notes from my instructor. These notes outline the geometric expression of the transitions and the continuity requirements for tangential fields at the boundaries. However, I’m unclear about:From Continuity to Amplitude Equations: How do I move from the boundary continuity conditions (for both electric and magnetic tangential components) to the explicit amplitude equations for the reflected and transmitted modes?Fourier Decomposition: I know I need a two-dimensional Fourier expansion (to handle the various possible TE/TM modes at each boundary), but how exactly should I set up this expansion? Which terms are essential, and how do I practically match them to obtain the reflection coefficients?Step-by-Step Method: I’m looking for a more detailed, step-by-step explanation or reference—rather than just a general outline—that clearly shows how to apply these conditions, derive the amplitude relations for each mode, and then compute the reflection/transmission (and thus the attenuation) through each section.Any concrete guidance, references, or illustrative examples would be greatly appreciated. Thanks in advance for your help!https://math.stackexchange.com/questions/211689/real-valued-2d-fourier-series

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 23, 2025, 05:03:59 pm
content: Sorry. Can't help much. This paper may help you.https://www.researchgate.net/publication/329466345_Mode_Matching_Method_for_the_Analysis_of_Cascaded_Discontinuities_in_a_Rectangular_Waveguide
Help with weird voltage/reading on HP 3456A - Page 1
Forum section: electronics / beginners

author: denimdragon
author_rank: Regular Contributor
timestamp: September 11, 2019, 09:38:29 pm
content: My HP 3456A has been reading low for a week (see photos) or so and I have no clue what I did OR if Idid anything to cause it.I usually null it when I’m checking resistance but that’s all I can recall doing to it. Any help would be greatlyappreciated before I start digging through the manual unaware of what I’m looking for to correct…

author: 0culus
author_rank: Super Contributor
timestamp: September 12, 2019, 03:41:57 am
content: I have a couple of 3455s; they have more primitive math functions than the 56, but I bet the 56 still has a scaling function. Have you triggered that accidentally? If you have some constants stored as Y and Z, and scaling is enabled, this could explain the readings being off.

author: dietert1
author_rank: Super Contributor
timestamp: September 12, 2019, 06:03:23 am
content: I would try operating the front-back switch several times. It needs movement every now and then.Regards, Dieter
Help with wiring Chinese PSU to spindle motor - Page 1
Forum section: electronics / beginners

author: matskublaster
author_rank: Newbie
timestamp: August 23, 2016, 10:17:57 am
content: Hi! Long time lurker and watcher of EEVBlog on youtube hereFinally registered an account on the forums and I kinda need some help since google turns up nothing on the specific power supplyI've been using a spindle and PSU from ebay (china) in conjunction with my shapeoko 2 set, to engrave signs and such that i've been selling. Everythings been running great for a long time, but recently the power supply went on the fritz and I had to go shopping for a new one, so I ordered one from ebay. Problem is the new power supply came with no documentation and the markings are in ChineseThis is all the info the ebay seller listed:Input voltage ?AC220VDC?0?110VThe armature voltage output: DC0 ~ 110VExcitation output voltage: DC110VOutput current: 6ADimensions: 190mm x 105mm x 60mmMatching motor power: 50W ~ 800WSupport manual potentiometer control, 0-5V/0-10V analog control and MACH3 software G code speedI've also include pictures from the ebay listing and pictures of the actual product i recieved (which is all in chinese)I need to connect it to a 220v AC wall outlet (L, N, ground) and to my 500w 110v DC spindle motor. It also came with a potentiometer, which I'm not to sure where to put.I would really appreciate it if someone had any idea how I should wire this thing!

author: thunderbolt87
author_rank: Contributor
timestamp: August 23, 2016, 10:50:57 am
content: Hi!Can't help you with the chinese but...Are you sure you want to power this thing up?Doesn't look trustworthy at all. Just look at that pathetic 110/220V switch.Is it there to select the (a) motor voltage or the (b) mains voltage?Unfortunately, if you fail to select the proper position may destroy(a) your motor or (b) the PSU.Even if you find the right position, your cat might come to another conclusion...Just be careful with that thing! And check your insurance policyCheers

author: Bukurat
author_rank: Regular Contributor
timestamp: August 24, 2016, 12:03:14 am
content: I just tried searching on some keywords from your description and found this at aliexpressThe photos on the page show wiring.http://www.aliexpress.com/store/product/300w-400w-500w-Dc-speed-control-power-supply-for-50-500w-motor-110v-220v-input/324800_32235098062.html
HELP - Page 1
Forum section: electronics / beginners

author: mateo123123
author_rank: Newbie
timestamp: October 07, 2013, 07:54:51 pm
content: Hi, im mateo, im really good at software, and know a lot about electricity and a enough about circuits, but whats something i can do over a weekend and less than $20 USD for circuitry.

author: mtbolha
author_rank: Contributor
timestamp: October 07, 2013, 08:09:05 pm
content: HahaNice oneThis is not even a bad project! It whould look nice as decorative piece and it whould be unique... for everyone that is not good at electronic

author: shk1d29
author_rank: Contributor
timestamp: October 07, 2013, 08:33:33 pm
content: Looks like you found a bug in the system. Or the bug is the system.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 07, 2013, 08:35:05 pm
content: Quote from: mateo123123 on October 07, 2013, 07:54:51 pmBuild yourself a shed, and put up a light in it.
helpe whit a arduino program to a ROV - Page 1
Forum section: electronics / beginners

author: Edwin the inductor
author_rank: Newbie
timestamp: July 09, 2020, 09:32:31 am
content: Hello!I need help. I am working on subwater ROV with one transmitter arduino and one recierver arduino. After a lot of work without getting the two boards to communicate reliably I have decided to use a principle that follows in the end of the text. Now the problem is that if I press a button I get output but when I release the button the output does not end but just continues.Can somone help me understand what I´m doing wrong?#include <Button.h>// create a button objekt for each gpio in use:Button btn1(48);Button btn2(50);Button btn3(52);void setup() {// starta buttons:btn1.begin();btn2.begin();btn3.begin();pinMode (22, OUTPUT);}void loop() {// if the 2 buttons is presed GPIO 22 goes HIGH:}if (btn1.pressed() && btn2.pressed()){while(!btn1.released() && !btn2.released()){digitalWrite (22,HIGH);}}//if the 2 buttons is relased GPIO 22 goes LOW:if (!btn1.pressed() && !btn2.pressed()){while(btn1.released() && btn2.released()){digitalWrite (22,LOW);}

author: Manul
author_rank: Super Contributor
timestamp: July 09, 2020, 02:59:36 pm
content: Well, I see some mess with curly brackets. It should not even compile. Also button logic seems to me unnecessary complicated. I do not know how your button library works, but something like that should be possible and is more simple, because you already have a loop provided by arduino environment.Code:void loop() {if (btn1.pressed() && btn2.pressed()) {digitalWrite (22,HIGH);} else {digitalWrite (22,LOW);}}