hybridfree/eevblog-posts huggingface dataset:
Troubleshooting a not working level-shifter circuit - Page 1
Forum section: electronics / beginners

author: hitech95
author_rank: Regular Contributor
timestamp: July 18, 2018, 01:53:51 pm
content: Hello,as a title I created a small circuit to interface a SIM800 module with an Arduino. (See the one used on the datasheet, 2 bypass on both rails 100nF and a 10K pullup for OE)Unfortunately communication does not work. I tried to replace the GSM module with an FTDI adapter and tried to read a serial output from the arduino. I tried to put a 50hz and 1khz square wave on side A and checked if on the opposite side I got something but i got nothing.To note after the failed attempt with the 2.8V of the SIM800 IO I decide to do some test on a more standard voltage: 3.3V on side A and 5V on side B.The pin has an intermediate value between the supply of the side from which I am analyzing and the other.Thinking I had blown with the soldering temperature when I replaced the chip, but the second and third gave a similar problem.In one case I obtained random characters as if there were a GND problem. (Not the case due to the power supply that share the same ground on both 5V and 3.3V rails)I tried to apply a pullup resistor to one side to see if the other side pin was miming the behaviour. But that pin was stuck on "HI" even if on side B i was settingthe pin back to GND.I used the same chip back in time when I was working on a serial connection between the RPI and a arduino. In that case i was having similar problems but those was due to some fake ics I got from ebay...the one i'm using right now are from farnell/element14.I don't have lots of equipment to test this out. (I don't have even have a proper scope)If someone have an idea on what is going wrong I would appreciate that.I'm still learning so it may be a dummy mistake!Thanks,hitech95Datasheet:http://www.ti.com/lit/ds/symlink/txb0108.pdf

author: hitech95
author_rank: Regular Contributor
timestamp: July 20, 2018, 03:41:11 pm
content: I started wondering if there is a problem with the OE pin...This IC is used in a lot of boards with configurations similar to the one i'm using....

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 20, 2018, 04:36:52 pm
content: The OE is active low, so tie it to VSS

author: hitech95
author_rank: Regular Contributor
timestamp: July 20, 2018, 04:47:54 pm
content: Section 8.3.4"The TXB0108 has an OE input that is used to disablethe device by setting OE = low".Actually by removing the pullup and putting VCCA directly on OE I have got a working state by toggling the pin manually.But it is till having problems with signals. I get a odd voltage in between the supply and ground.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 20, 2018, 06:55:48 pm
content: yep, sorry, I got it the wrong way. Watch out for the decoupling of the supply voltages, add to both VCCs 100n as close as possible to the supply pins
Troubleshooting a Samsung CRT SyncMaster 1100df - Page 1
Forum section: electronics / beginners

author: 13hm13
author_rank: Frequent Contributor
timestamp: August 14, 2013, 11:06:24 am
content: The front panel pwr on/off push button has an "idiot" green LED light that indicates three conds:ON (solid) -- on with signal (CRT should display input signal or monitor-generated menu)ON (blinks) -- on with no input signal (CRT should display monitor-generated menu or scrolling "NO INPUT SIGNAL" text message)OFF (unlight) -- pwr off (main pwr push-button in out position), or no pwr (unplugged, damage, etc.)I have solid on pwr button LED, but no CRT image-- not even Samsung's own internal-generated menu. Powering switch OFF and re-powering, I get the usual 2-3 sec delay and then the pwr LED turns ON.All the ICs I can stick my probe on seem to be getting clean 5VDC. But the normal "bang" of the HV section does not happen. Dunno whether HV is bad or whether HV isn't getting signal to turn on.What's weird is the solid pwr button LED, noted above. It should blink if there is no input connected. But it is solid regardless of the presence of input.Any quick ideas?Thx!!

author: Psi
author_rank: Super Contributor
timestamp: August 14, 2013, 11:18:48 am
content: Plug the monitor into a PC, so it should be showing an image, now put a torch right up against the screen at a 45deg angle.Get in close with your eyes and see if you can see any image or patterns.Sometimes the backlight dies but the LCD is still running fine.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 14, 2013, 11:23:19 am
content: Quote from: Psi on August 14, 2013, 11:18:48 amLook at the 'CRT' in the subject...

author: SeanB
author_rank: Super Contributor
timestamp: August 14, 2013, 05:38:46 pm
content: Check power supply outputs, there should be a 100-150V rail to the LOPT area that provides power there. You can measure it at a test point by the power supply, which will have the voltage marked there. Common faults are the line output transistor pops or the LOPT has dry joints on the pins, or the tuning capacitors there have dry joints. Also common is the LOPT dying internally. Another fault is the CRT drivers on the input board going faulty, you will see the cooked capacitors and resistors there in that case.

author: Tita
author_rank: Contributor
timestamp: August 14, 2013, 08:09:30 pm
content: Monitor repaire videos:1)2)Classic Monitor Repair 02 of 033)1)CRT monitors-Part 1of 42)CRT monitors-Part 2 of 43)CRT monitors-Part 3 of 44)CRT monitors-Part 4 of 4

author: Stonent
author_rank: Super Contributor
timestamp: August 14, 2013, 11:30:20 pm
content: Lick your fingers and touch random things, if you fly across the room, then the flyback circuit is working.If you don't survive, then it was working very well.

author: G7PSK
author_rank: Super Contributor
timestamp: August 15, 2013, 03:18:07 pm
content: Quote from: Stonent on August 14, 2013, 11:30:20 pmThat always works.
Troubleshooting AFSK Caller ID Decoding Issues from ATA - Page 1
Forum section: electronics / beginners

author: hitech95
author_rank: Regular Contributor
timestamp: August 01, 2025, 11:10:08 am
content: Hello,I’m working on writing software for a VoIP device using a SLIC chip, specifically for AFSK caller ID encoding.I’m using the SLIC chip to send data that is converted into an AFSK signal.I am not backfeeding the POTS but am working on the software side of an Analog Telephone Adapter.The chip should automatically handle the start and end frame bits. (I should only put the data into the fifo and turn the FSK block on)I send a preamble before the MDMF data.The issue:The phone does not seem to decode the Caller ID correctly (nothing show up it only ring).I’ve tried to send the data between ring pulses and with line inversion before the first ring, but it’s still not working.My understanding of ETSI EN 300 659-1, the Caller ID signal should be transmitted between the ring pulses,specifically during the first ringer idle (section 6.1.1), which is also confirmed by my ISP documentationso I should be using the right standard.I have a scope connected to the tip/ring with a probe in AC coupled mode (x10), measuring 145mVRMSsignal.The DC offset is about -47V, and I have the phone connected in parallel (on-hook) so the line should be properly loaded.Possible causes I suspect:The data packet might be malformed on my side.Timing issues between preambles, marks, etc. (though they should be correct).Questions:What other measurements should I take to troubleshoot the issue?What can I build to decode the signal? Just to check if the decoder locks in and the data is correct.Any tips on what I might do to better troublesahoot this?My pseudo-code:Code:# Ensure OFFHOOK ActivesetLineFeed(Linefeed.IDLE)time.sleep(0.5)# 1st Ring BurstsetLineFeed(Linefeed.RINGING)time.sleep(2)# OHTsetLineFeed(Linefeed.IDLE_OHT)# Delay 500 to 2000ms See T5 in Fig.4time.sleep(1.2)# Send data with 32 byte preamblesendFSK(data, True)# Delay more than 500ms See T6 in Fig.4time.sleep(0.75)# Second RingingsetLineFeed(Linefeed.RINGING)time.sleep(2)# Go back to IDLEsetLineFeed(Linefeed.IDLE)BTW this is a hobby project on attempting to re-create a open source implementation of a proprietary deprecated firmware.While POTS is almost deprecated by itself it was a great project to start using my first scope.
Troubleshooting AS1424 spectrum analyser - Page 1
Forum section: electronics / beginners

author: msknight
author_rank: Regular Contributor
timestamp: June 12, 2021, 08:50:52 pm
content: I've got a feeling that I'm on a hiding to nothing here, but here goes :-)AS1424 audio spectrum analyser. This one is version 6.1 and I think is prior to 2016.I've built the kit but it won't power on. I've checked the cable and I've also checked my socket soldering, and they're good. However, I'm not sure how to start troubleshooting... and I know, for a beginner like me, perhaps I've chosen the wrong thing to start going to town with, but nothing ventured, nothing learned.I think I've got a problem because the chip looks to have been lasered,(it was pre-soldered to the board)but it seems to be programmable, so there's a chance that someone might know what it is likely to be... and therefore which pins to check for power. The only spec given for that chip in the assembly instructions is, "CPU."I do have a v7 working, and another v7 that I'm in the process of building, so I'm starting to think that there's a problem with the 6.1 that I won't be able to solve.Part of me is also thinking that the LEDs are controlled by the chips at the top which I think are ULN2003 and 74HC595, so I'm wondering that with a small arduino or something, I might be able to rescue this rather than chuck it in the bin... but that's further down the line.Anyway... I'm good at getting myself into these scrapes (cough) opportunities to learn and grow... and I'd be grateful for any thoughts please.
Troubleshooting basic drone  - Page 1
Forum section: electronics / beginners

author: Seaofdep
author_rank: Regular Contributor
timestamp: September 21, 2017, 05:57:37 pm
content: Hi , I have a propel orbit hd drone that was working fine, and after a rough landing I replaced the propellers. Tested and was working. The following day I turned on the drone and only 1 led out of the 4 light turns on doesn't blink for connecting to controller or anything. I have looked at many forums and found that propel is not the best at helping out or responding. So decided to pull out the dmm. I found that the working arm is receiving 4ish V and 2 of the non working are at 0.032-0.053 and the last is receiving no power at alll. I am not sure where to begin checking for the shortage and would appreciate any feedback and or help. Thank youSent from my iPhone using Tapatalk

author: Seaofdep
author_rank: Regular Contributor
timestamp: September 21, 2017, 06:01:15 pm
content: The working is led2 I have also tested all led and they are in working order

author: Seaofdep
author_rank: Regular Contributor
timestamp: September 26, 2017, 06:23:05 am
content: Quote from: Seaofdep on September 21, 2017, 06:01:15 pmWell after countless of hours on google and determination , I managed to sniff around with the dmm and find the issue . Now I just need to figure out how to desolate these little smd lolSent from my iPhone using Tapatalk

author: Seaofdep
author_rank: Regular Contributor
timestamp: October 22, 2017, 04:46:04 am
content: Quote from: Seaofdep on September 21, 2017, 05:57:37 pmSo just wanted to update this. I tried replacing smd and that shorted out on main board but even with a rework station it was difficult lol and ended up flicking of other components. When all hope was lost, I remembered about a micro drone with bad motors I had (2x2). Long story short , I made sure mosfet can handle the amount of amperes needed to run bigger motors , modified and added long range antenna, soldered motors and new battery wires. Zip tied main board and now she fliesSent from my iPhone using Tapatalk
Troubleshooting beverage cooler control board. - Page 1
Forum section: electronics / beginners

author: freak
author_rank: Contributor
timestamp: October 03, 2025, 02:41:29 am
content: My beverage cooler failed. Compressor doesn't start. The compressor works fine. I do not have a schematic. The controller board has a 12v relay to turn on the compressor and it is not energized. The led display at the front works and displays temperature. When I look at the relay coil with a meter it shows 5v. I've attached an image from my scope that shows what is at the relay coil. Obviously not a clean 12v. Could this be as simple as filter caps?

author: jwet
author_rank: Frequent Contributor
timestamp: October 03, 2025, 02:20:52 pm
content: Attached is a rough schematic. The power supply is similar to a Power Integrations LP type- chinese clone. Its not clear how the line in gets to it, you can trace. I would look at the larger caps. On the primary, the HV cap marked PC1 and on the LV side. Most likely issue is a cap. HV Cap would be most suspect. See photo- this is approximately

author: freak
author_rank: Contributor
timestamp: October 03, 2025, 09:50:20 pm
content: Wow thank you very much!!! Can't wait to dig back into it!!

author: freak
author_rank: Contributor
timestamp: October 03, 2025, 11:56:12 pm
content: Just checked and the DC voltage looks clean on the high side. I'll replace the low side caps.

author: freak
author_rank: Contributor
timestamp: October 07, 2025, 01:02:20 am
content: I replaced the cap on the 12v output and it runs like a dream. @jwet Thanks again for your help!!!!

author: jwet
author_rank: Frequent Contributor
timestamp: October 07, 2025, 02:29:25 pm
content: Great to hear! Use the thanks button, its how I measure my impact.
Troubleshooting ESP8266 Startup Issue with Viper22A - Seeking Insights - Page 1
Forum section: electronics / beginners

author: Shubham
author_rank: Contributor
timestamp: December 31, 2023, 03:38:30 pm
content: Hi everyone,I encountered an interesting issue with my SMPS-powered ESP8266 (ESP-12F), where the program would only execute if I manually pressed the RST button on power-up. After some investigation, I discovered that the culprit was the VDD capacitor (22uF/50V 0805 ceramic) on the Viper22A.Initially, adding a 1K resistor across the 5V output of the SMPS seemed to solve the problem for a few circuits. However, when I removed the resistor and sought an alternative solution, I replaced the ceramic capacitor with a 10uF 63V aluminum electrolytic capacitor, which resolved the issue.Curiosity led me to experiment with different values of ceramic capacitors (1uF, 4.7uF, 10uF, 22uF). Although some seemed to work initially, they proved to be an unreliable replacement for the aluminum electrolytic capacitor.I'm reaching out to the electronic community to gain insights into the significance of using an aluminum electrolytic capacitor instead of ceramic for VDD (startup) of Viper22A. Your expertise and experiences would be greatly appreciated.Thank you!
Troubleshooting first PCB - Page 1
Forum section: electronics / beginners

author: JLynch
author_rank: Contributor
timestamp: August 20, 2021, 04:23:01 am
content: Troubleshooting my first PCB and hit a wall. Fairly simple board, 5v USB power, 3.3v regulator for Bluetooth & Serial Interface and H-Bridge.Both 5v and 3.3v check out as do the Bluetooth & Serial Interface, H-Bridge has power and properly grounded. Checked the Bluetooth GPIO pins to insure they can be set high / low. Traced motor wires back to the H-Bridge to confirm all’s good, there’s just no output.My PCB pretty much matches everything on my breadboard test circuit, all the same components / chips only difference is that I’m using individual breakout boards in my test circuit that have ‘built-in’ caps, resistors and such for both the H-Bridge and Bluetooth.It’s behaving as if the H-Bridge is stuck in Sleep mode so I went back through the TI datasheet and it calls for a 20 to 75K pull-up resistor. Wasn’t sure what value to use so I copied the DRV8833 breakout board in my test circuit and used 47K.Not really sure where to go from here, again Bluetooth is working, successfully made remote connections, used the serial interface to make configuration changes, power, grounds, status LED all good just no output from the motor driver.Any help or suggestions would be greatly appreciated.https://www.ti.com/lit/ds/symlink/drv8833.pdf

author: grrmachine
author_rank: Contributor
timestamp: August 21, 2021, 08:44:34 am
content: Hi,Can you share your PCB/layout pictures? And how big is your motor? With a 1current shunt, you are limited to 200mA current. Try to short the current sense resistor and see if the motor actuates then? See if pin no 8 (nFAULT) is low?Also, your schematics is not in parallel mode.
Troubleshooting Laser Diode (From Color LaserJet) - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: September 24, 2018, 05:45:37 pm
content: Hello all,I am trying to troubleshoot the laser scanner assembly on my laser jet. The fault codes indicate a problem with the laser assembly (more specifically the Yellow diode - Code 51.23). I wanted to try to probe the diodes and see if they work.How would I do this? Can I simply probe with my multi-meter on diode check? What output should I expect? I mean, I take it it is invisible light. Should it "burn" a piece of paper? I have no specs on the diodes in use.Also, what probe points should I use? I take it LD is Laser Diode, COM is GND but what about PD?I've attached a picture of the board.Thanks in advance,

author: tomato
author_rank: Regular Contributor
timestamp: September 24, 2018, 06:20:25 pm
content: Quote from: made2hack on September 24, 2018, 05:45:37 pmPhotodiode?

author: made2hack
author_rank: Frequent Contributor
timestamp: September 25, 2018, 06:19:26 am
content: I guess, but how should I try to probe?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 25, 2018, 06:44:32 am
content: The 3 pin laser diodes have an internal photodiode. One could do the normal diode test, but this would not tell much, as a broken laser diode is likely still a working LED, just a little dimmer.Laser diodes are also very ESD sensitive - about as bad as small unprotected MOSFETs. So un-soldering them is not a good idea. Even the DMM in circuit can be a problem.The next problem is that the optics needs to be aligned.So I am afraid, that the laser diode removed from the board essentially means it is beyond a realistic repair.The realistic check would be to reverse engineer the driving circuit part and than compare the driving current and PD current from a working on the problem channel.

author: made2hack
author_rank: Frequent Contributor
timestamp: September 25, 2018, 07:10:42 am
content: Hi Kleinstein,Thanks for your input. So the photodiode is there to excite the laser? To get it to "lase" ?This was more a trip down a rabbit hole until a replacement laser scanner arrives.As for alignment, they are still in the original factory holder. The PCB you see was soldered in place after the diodes were fixed.For anyone interested, I've attached a generic schematic of other laser diodes.

author: tomato
author_rank: Regular Contributor
timestamp: September 25, 2018, 07:47:19 am
content: Quote from: made2hack on September 25, 2018, 07:10:42 amNo, the photodiode is just used to monitor the output.
Troubleshooting microcontroller based audio device - Page 1
Forum section: electronics / beginners

author: artran
author_rank: Newbie
timestamp: August 23, 2020, 02:18:28 pm
content: Hi,I have an Arcam rCube iPod speaker that no longer does anything useful. It has an external line-in but I can't get it to switch to it. I have obtained a full schematic from Arcam's website and done some troubleshooting and it looks like all of the peripheral bits like keypad/display, DSP, and amplifier are working as I was expecting but the microcontroller seems to be totally inactive. For example I can see I2C signals from the keypad but I can't see the micro initialise the 74HC595 that is attached to it to extend its IO.This has made me focus on the micro to see if I can identify any issues with it. So far I've verified its supplies seem OK - it takes a 3v3 supply for IO and generates a 1v8 supply for its own core. When I look at the crystal oscillator I'm not sure if what I see is correct; it appears to be running in that I can see a 12MHz sine wave on both of the crystal's pins but the voltages on the pins seem to be lower than I expected. One side has 0.8V pk-pk and the other side has 1V pk-pk. Does that sound reasonable or not? If it's fine is there anything else that you can suggest I should look at?The micro is an Atmel AVR (AT32UC3B) in case that's relevant.

author: Manul
author_rank: Super Contributor
timestamp: August 23, 2020, 04:46:13 pm
content: Crystal amplitude seems ok. Look MCU reset circuitry, try to analyze, maybe firmware is waiting for some kind of signal to continue booting and never gets it? For example "power good" or similar critical signals.Probably there should be no I2C signals if MCU is not functioning, because almost guaranteed that keypad is a slave. So it should mean that it is running. Well, as far as my experience goes.

author: artran
author_rank: Newbie
timestamp: August 23, 2020, 05:36:50 pm
content: Thanks for confirming the crystal seems OK and for the suggestions on where to look next. There are a couple of candidate signals so I'll check them later.I initially thought that the I2C might be showing me that the micro was alive but the keypad has its own controller so I think it can generate I2C and an interrupt that go to the micro. There is another I2C and two SPI buses but they seem to be constantly idle.I'll report back on anything i find.Cheers,
Troubleshooting Microprocessor Based Systems  - book recommendation - Page 1
Forum section: electronics / beginners

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2013, 10:56:36 pm
content: To those new to diagnostics and troubleshooting on microprocessor based systems, I have a book recommendation for you.Title: Troubleshooting Microprocessor-Based Systems NOT TroubleshootingonMicroprocessor-Based SystemsAuthor: Allan H Robbins / Brian LundeenISBN: 013931296X and 978-0139312960Amazon:http://www.amazon.co.uk/Troubleshooting-Microprocessor-based-Systems-Allen-Robbins/dp/013931296X/ref=sr_1_1?ie=UTF8&qid=1372805497&sr=8-1&keywords=Troubleshooting+Microprocessor-Based+SystemsI bought this book because I am currently working on a high density MC68340 based embedded computer that HALTS during boot. A nasty fault to tack down as I have no support or information from the manufacturer. I have been hunting around for some guidance on the best approach to take.This book arrived this morning and has been an excellent read. It answered all of my questions and concerns regarding diving into a non responsive embedded computer that is providing no fault codes.The book is available cheaply in the used marketplace. It was so useful and cheap that I bought a spare
Troubleshooting videos - Page 1
Forum section: electronics / beginners

author: Enron
author_rank: Contributor
timestamp: January 10, 2013, 09:58:19 pm
content: I was curious, if Dave has made any general troubleshooting videos. I watch his repair ones, but I was wondering if there was a "Troubleshooting tips" video. Thanks!

author: EEVblog
author_rank: Unknown
timestamp: January 10, 2013, 10:39:45 pm
content: I'm sure there are quite a few with troubleshooting various things.But just a general "how to", no.Dave.

author: w2aew
author_rank: Super Contributor
timestamp: January 10, 2013, 11:32:47 pm
content: While not up to the caliber of Dave's videos, here is a troubleshooting video that I did a few months ago - tracking down a noise problem with one of my function generators:

author: Enron
author_rank: Contributor
timestamp: January 11, 2013, 01:47:49 am
content: Thanks Dave, thanks w2aew!
TRS switch question.  - Page 1
Forum section: electronics / beginners

author: xgpt
author_rank: Newbie
timestamp: May 11, 2024, 12:53:06 am
content: https://www.cuidevices.com/product/resource/sj1-352xng.pdfWhy are there (detection?) switches on the SJ1-3524NG on tip and SJ1-3525NG on both tip AND ring?What would the possible benefit be of the second detection switch? I'm sure I'm missing a very obvious use-case here.I'd also really love advice on how to answer this kind of question for myself without having to lean on communities like this to grok other people's brains who might have used this stuff themselves.

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 11, 2024, 02:11:16 am
content: Because it's not so much a "detector" switch than just a switch.ie: In the old days, they simply used these contacts to turn off the speakers (left and right) when you plugged the headphones in.

author: xgpt
author_rank: Newbie
timestamp: May 11, 2024, 02:21:23 am
content: Is there a way to figure out if what is plugged in is a stereo or a mono jack? I'm struggling to envision the circuit required for that task.

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 11, 2024, 02:37:50 am
content: You could detect that the right channel is shorted to common/ground since the "ring" on a mono jack is missing. (part of the sleeve)

author: xgpt
author_rank: Newbie
timestamp: May 11, 2024, 02:53:15 am
content: Yeah, but would I need the additional ring switch to do that detection? I can't see why I would.

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 11, 2024, 02:59:52 am
content: You are correct. No switch feature would be required. The SJ1-3523NG would work for that.

author: wasedadoc
author_rank: Super Contributor
timestamp: May 11, 2024, 01:59:42 pm
content: Quote from: Kim Christensen on May 11, 2024, 02:11:16 amYour diagram is incorrect. Convention is for the tip to be left audio, not right.

author: tooki
author_rank: Super Contributor
timestamp: May 11, 2024, 02:25:31 pm
content: Quote from: wasedadoc on May 11, 2024, 01:59:42 pmIndeed. I remember it from the mnemonic “red, right, ring”.The second diagram Kim C. posted later is correct, though.

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 11, 2024, 02:58:09 pm
content: Quote from: wasedadoc on May 11, 2024, 01:59:42 pmRight.
True beginner's video - Page 1
Forum section: electronics / beginners

author: FenderBender
author_rank: Super Contributor
timestamp: February 20, 2013, 03:43:33 am
content: Hey guys,Not sure why I'm bothering posting this here since I think most people here are far past this state, but here's my new video:Well if you bother to watch it, be sure to tell me what you think. It's a bit lengthy.
True RMS Current Measurement - Page 1
Forum section: electronics / beginners

author: MITTS
author_rank: Contributor
timestamp: June 09, 2015, 12:45:10 am
content: Hi guys,Would a Fluke 87V be displaying a True RMS current reading if a i200s Clamp is being used?TIA

author: dom0
author_rank: Super Contributor
timestamp: June 09, 2015, 08:15:30 am
content: If you put it into AC Volts mode.

author: MITTS
author_rank: Contributor
timestamp: June 10, 2015, 08:27:52 pm
content: ThanksWasn't sure if it would measure true rms same as the regular i200
solved: Truth table for '331 comparator open collector output polarity - Page 1
Forum section: electronics / beginners

author: incf
author_rank: Frequent Contributor
timestamp: April 17, 2025, 01:19:10 pm
content: Where can I find a truth table for a '331 comparator?For some reason I find I make more mistakes with open collector devices than push-pull (and I've got the faint idea in the back of my mind that the output polarity might be inverted for an open-collector comparator vs a regular op-amp?)edit: I think I found it
TRW transistors - Page 1
Forum section: electronics / beginners

author: geggi1
author_rank: Frequent Contributor
timestamp: July 13, 2015, 05:05:20 pm
content: HI!I have got about 10 TRW TPV583 transistors and have been looking all over for information about these transistors.Is there anboty that can point me in the correct direction to find a datasheet for these transistors?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 13, 2015, 06:51:05 pm
content: 1. Can you post a picture with all the markings?2. Do you have datasheets for similar devices?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 13, 2015, 09:11:52 pm
content: I also have questions about TRW transistors. I'd love to see a databook or catalog or something (probably 70s vintage). Haven't seen such a thing in the usual places.Tim

author: Stonent
author_rank: Super Contributor
timestamp: July 14, 2015, 06:39:09 am
content: I've seen TVP on transient voltage suppressors.

author: geggi1
author_rank: Frequent Contributor
timestamp: July 15, 2015, 09:02:12 pm
content: The transistors wher e pullled from som old 800Mhz (i think) radiolink equipment.on the boards I also pulled some BFQ68 and BFQ38.Link for some TRW transistors.http://f6csx.free.fr/DOC/VRAC/I was hoping that these transistors might be equivalents to the BFQ transistors or be higeher power.I'm planing to build a 23cm PA something like.This:http://www.qsl.net/iw2bc/pa1w_atv.htmlOr this:http://www.qsl.net/iw2bc/pa2w_atv.html
Try to understand this electronic load circuit - Page 1
Forum section: electronics / beginners

author: chancs
author_rank: Contributor
timestamp: September 28, 2019, 02:53:18 pm
content: Dear All,If you look at the image below, I circled 3 sections with red and labeled them 1,2 and 3. So here are the 3 questions that I want to ask.Q1. What is the purpose of this 1nF cap? Just there to form a low-pass filter with R3 to reduce input noise?Q2. In my limited understanding, this 10nF is there to do loop compensation. However, in Scullcom implementation, he also put a resistor in series with that capacitor. So which one is more correct?Q3. I really don't understand this. Doesn't look like a low-pass or high-pass filter to me.Thanks,SamFigure 1Image taken fromhttps://www.eevblog.com/forum/beginners/struggling-with-dc-load/msg2698044/#msg2698044Figure 2Scullcom implementation

author: GerryR
author_rank: Frequent Contributor
timestamp: September 28, 2019, 11:38:50 pm
content: It looks to me that "1" is just a decoupling cap to limit noise going into the op-amp which is driving the FET. (If you do the math, it filters above 30 KHz - hi-freq. Not sure of "2" though it looks to be a non-inverting integrator drive for the FET to keep the gate drive real steady. "3" is just an R-C snubber to protect the FET (R-C about 5 uS, if that is 2.2 ohms and not 2.2k).
Achieving ZVS / ZCS in a LLC resonant SMPS circuit - Page 1
Forum section: electronics / beginners

author: tigrou
author_rank: Regular Contributor
timestamp: November 13, 2024, 12:01:02 pm
content: I have created the followingcircuitin Falstad.It's a half-bridge LLC resonant circuit.The resonant frequencies should be as follow : 112.5 Hz, 159.1 HzAt 112.5 Hz, the current following through the LLC circuit seems to be perfectly synchronized with the switching frequency : it occurs almost exactly when current is 0 (ZCS).Here is the voltage / current going through the up side mosfet (you have to reset simulation to see this) :At 159.1 Hz, according to the chart below, it should achieve ZVS.I don't really understand what ZVS means nor how to measure it.
Trying to build a metal detector. - Page 1
Forum section: electronics / beginners

author: Refrigerator
author_rank: Super Contributor
timestamp: March 24, 2015, 06:55:18 pm
content: Hey.the title says most of it. I'm trying to build a metal detector that would be stable and sensitive. I've built one already, it's "the metal detector MK II" circuit but it's unstable and hard to set up, the sensitivity tends to start drifting up or down and I can't get to that sweet spot where it's the most sensitive.I want to do something similar to that one, but i'm thinking of using a Colpitts oscillator instead of the one in the circuit of the MK II and i also have plenty op-amps laying around to use, so yeah why not use those.I want to make the colpitts oscillator resonate and the inductor would be my Tx coil, while i could do the sensing part with op-amps, i have many quad op-amps from a vintage audio receiver ( too many actually ) one of them i think could be just a buffer, maybe with a gain setting, while the other one would be for the sensitivity setting, yet i'm not sure about how should i go about doing the receive coil.What i'm asking is would it be possible for the colpitts oscillator to effectively drive the Tx coil and if it would be powerful enough to do it without getting stopped, and also where could i find a simple formula to set the colpitts oscillator to work.Thanks for help.Ps: my selected frequency is about 33kHz.
Trying to decode SMD chip/module number - Page 1
Forum section: electronics / beginners

author: johnkeates
author_rank: Contributor
timestamp: August 08, 2017, 07:40:06 pm
content: Hi, I have a picture of a chip or module (seems like a BGA with a space in it for some support components) what is supposed to do 802.11 and possibly Bluetooth as well (it's used in a Samsung phone). While I don't need to buy one, I do wonder how to decode the part number on it:2749m3e708b9A picture is available at:https://stellatech.com/en/samsung-sm-g850f-galaxy-alpha-wifi-ic-wlan-module,a,817641.html/(it's zoom-able and has another showing the underside)I know a number of memory chips that have short codes on them because there is no space for the full partnumber and production number because of the small size, so they use short codes that can be expanded to the full number, but for this kind of chip I have no idea where to start. It could be Broadcom, but might as well be any of the other brands (Realtek? Atheros? RaLink?).

author: amyk
author_rank: Super Contributor
timestamp: August 09, 2017, 02:01:10 am
content: The part numbers had absolutely NO results in Google, so that lead me on an interesting journey --- from finding the schematic for that phone, to determining it's an "SWB-B80" module, which lead to identification of it containing likely a BCM4354, aninteresting datasheet for a related but not identical module, andSamsung's own subsidiary which manufacturers these "SWB" modules.

author: johnkeates
author_rank: Contributor
timestamp: August 11, 2017, 01:19:54 pm
content: Quote from: amyk on August 09, 2017, 02:01:10 amThat is one interesting rabbit hole! Thanks. I didn't think about actually trying to get the schematics for that specific phone, but that would have been the way to go of course.
Trying to derive equation out of lm317 datasheet - Page 1
Forum section: electronics / beginners

author: avogadro
author_rank: Contributor
timestamp: October 31, 2018, 04:52:12 pm
content: I was just trying to derive the equation for output voltage of lm317 for fun and I cant get it. Dont know what Im doing wrong. I attached the image of what I was trying to derive. The closest I get is V0 = Vref((R2 + R3)/(R1)) - 10.

author: spec
author_rank: Frequent Contributor
timestamp: October 31, 2018, 08:07:39 pm
content: + avogadroRevised schematic with formula for output voltage attached.

author: westfw
author_rank: Super Contributor
timestamp: November 03, 2018, 06:56:26 am
content: In your second picture: R3, D1 (a zener) and C2 essentially form a conventional -1.25 zener voltage regulator, with the -1.25V output at the D1/R3 junction.R1/R2 and the LM317 are the normal lm317 regulator, with the "adjust" input biased to -1.25V instead of ground. offsetting the normal 1.25V regulation point of the 317. (which tries to make sure that Vout is "Adjust+1.25V")

author: spec
author_rank: Frequent Contributor
timestamp: November 03, 2018, 11:02:38 am
content: Quote from: westfw on November 03, 2018, 06:56:26 amYeah, that is right. Just standard stuff, straight from the datasheet.
Trying to design a circuit - Page 1
Forum section: electronics / beginners

author: carlostex
author_rank: Newbie
timestamp: July 01, 2018, 12:27:32 pm
content: Hy there guys,here's a complete newb, who knows little of electronics and is trying to design something for a retro computer. So the setting is this:I managed to overclock a Tandy 1000 SL computer. This machine came originally with a 8086 CPU running at 8MHz. I replced the CPU with a pin compatible NEC V30HL which can run up to 16MHz. i noticed by taking a look in the SLtech manual that the OSC 24MHz goes into the buffer blue chip which divides the signal by 3 to supply the CPU with 8MHz. I took a look to see where the trace with the signal was, i i cut the trace, got a 48MHZ Oscillator, patched a wire into the spliced trace and basically i got a overclocked machine. If you don't believe it here it is:But i want to do this better. Basically i want to design a dual oscillator circuit that i control via latching switch. It would work like a turbo switch although i could maybe only switch it when the machine was off. This would be great as i would be able to use the Tandy in a variety of speed ranges, which would help with the games i want to play.I took my liberty to design a pseudo circuit. You know how when programmers write an idea in pseudo code? I did the same for my idea so i (poorly) made this drawing. This is where i need the help and knowledge to know if this is possible or not:

author: Paul Price
author_rank: Super Contributor
timestamp: July 01, 2018, 05:00:37 pm
content: You can easily switch between the two clock sources in many ways, here are some suggstions:1)Use a SPDT mechanical toggle switch mounted on the front panel to select outputs of a 14-pin bus driver (74HC126) that has three state output enables you can select with a SPDT toggle switch. You would use pullup resistors on the individual output enable pins(1k-ohm).2) You could even use a tiny 5V SPDT relay to control which oscillator source feeds the CPU.3)A bubba solution is just using a SPDT switch carrying the clock signals to a a front panel mounted toggle switch. Use twisted pairs to the switch contacts and it might work just fine. You might add a 330-ohm pullup resistor at the clock input to +5.4)A slightly less bubba solution that you can build with just about any genpurp NPN transistors you might find laying around, for example (2) 2N3904 transistors, both in common-base configuration, with the collectors connected tied together at the clock input on the CPU, using a 470-ohm pull-up resistor to +5, and a front panel SPDT switch grounding either of the 2N3904 bases. You bias both the bases each with a 1K resistor to +5 and a LED (anode to base, cathode to ground, both LED's bypassed with a .1uf cap from base to ground). Connect one emitter to each clock source.

author: glarsson
author_rank: Frequent Contributor
timestamp: July 01, 2018, 06:33:02 pm
content: Some circuits don't function well if you switch between two unsynchronized oscillators (as in the example) as this will sometimes generate short pulses (the active oscillator just went high and you switch to the other oscillator that is low).
Trying to drive a pmos - Page 1
Forum section: electronics / beginners

author: albert22
author_rank: Regular Contributor
timestamp: August 01, 2018, 03:23:29 pm
content: Hi, I am trying to make a buck preregulator based on a TL494. The unregulated input voltage is between 70 to 80v. Represented by V1 in the schematic. The TL494 ground will be at vun and it is represented by V3 its Vcc will be 16v referenced to vun. The PWM will drive Q3 (Vceo >100v). (Or perhaps a nmos). Q1 and Q2 are 2n2222 and 2n2907.The only way that I found to clamp the voltage at the collector of Q3 is by the diode D. Is there a better way to do it?I cannot use a dedicated gate driver ICSimulation seems to work. Of course I will recalculate all the resistors (their values are just for for the sim)I included a 15v zener between Gate and source of the pmos.Thanks for any help

author: Giaime
author_rank: Regular Contributor
timestamp: August 02, 2018, 07:20:00 am
content: Hi, I've noticed some strange behavior in LTSPICE if you leave the default "NPN" or "PNP" devices. Run the simulations with an actual device instead.Regarding your question, why you need to clamp Q3 collector? Why Q3 emitter is not at ground?You're also missing the recirculating diode and the inductor...Check this out:http://www.jiggerjuice.info/electronics/projects/power/buck-diode-pmos.html

author: albert22
author_rank: Regular Contributor
timestamp: August 02, 2018, 07:08:43 pm
content: Thanks for your answer Giaime.The buck regulator is already working at 16v input. That is why I showed just the driver. Now the TL494 collectors (pin 8 and 11) are driving Q1 and Q2.All the circuits that I found are low voltage. My input voltage is 80v max so the idea is to use a floating supply (represented by V2) for Q1 and Q2.I need the TL494 to be referenced to the negative of the input voltage (vun) so its output level should be translated to drive Q1 and Q2. It cannot drive those transistors directly because the max voltage that the TL can handle is about 30vI realized that placing a resistor in series with the collector of Q3 forming a voltage divider with R5, will work.For Q3 I found a MJ13003 in my junk box. So I going to try it tonight.Also I am going to find suitable values for the resistors to drive the gate of the mosfet as fast as possible without making them to low.If the smoke is not too dense I am going to post the final circuit.saluti affettuosi
Trying to figure out how to light up LEDs with a fast phone charger - Page 1
Forum section: electronics / beginners

author: chris0320
author_rank: Newbie
timestamp: June 16, 2020, 12:21:14 pm
content: Hey guys! First post here and I'm a noob when it comes to electronic components. I hope this is not too low level for this forum.I want to create a simple lamp for a decorative item (a gift for my GF), but I'm not really sure if it's going to work the way I want it.I want to use a 12V strip (a short strip with about 12 LEDs) and connect the open wires to a USB C female connector. Put that connector in the side of the housing and when she wants to light it up, she would connect her phone charger (I was also thinking of using batteries, but that just wouldn't fit).She has a Samsung Note 10. I've checked online, and as I found its charger can deliver: PPS: 3.3-5.9V / 3A 3.3-11V / 2.25A. I'm not sure how it would react if connected to a simple LED strip - does it give off 5V like a regular charger?Regarding the step-up converter, the housing is really small and I only found converters that would fit that have the max input of 1.0-2.0 amps. I dont know if it's an issue if the output of the charger is more than the input of the converter or if the charger wouldn't even give off 2.25 amps if the LEDs don't draw that much?Let me know if you need any more details.Thank you!

author: tunk
author_rank: Super Contributor
timestamp: June 16, 2020, 01:22:03 pm
content: All USB chargers should by default deliver 5V.Do you have specs or photos of the LEDs?

author: chris0320
author_rank: Newbie
timestamp: June 16, 2020, 01:39:32 pm
content: Thanks.No, I didn't choose a strip yet, but I want a white (non RGB) strip. Most of the ones I looked at were 60 or 120 LEDs/m/3.3f and around 5-10W/m/3.3f and I need about 18-20cm/7-8"

author: RenThraysk
author_rank: Regular Contributor
timestamp: June 16, 2020, 01:55:07 pm
content: Sounds like might be looking for a USB-C Trigger (USB decoy is another search term for them), to perform the USB-C negotiation to get your required voltage and provide it as simple DC output.

author: tunk
author_rank: Super Contributor
timestamp: June 16, 2020, 02:17:05 pm
content: 20cm should then draw 1-2W or ~300-600mA at 5V.Or it would be even simpler if you could find a 5V LED-strip.

author: ArthurDent
author_rank: Super Contributor
timestamp: June 16, 2020, 02:52:32 pm
content: Here's an eBay link to a listing of over 3000 USB LED strips. Some with converters, some without; some RGB, some white. There should be something there to give you some ideas if not work as is.https://www.ebay.com/sch/i.html?_nkw=usb+powered+led+strip
Trying to find 1 v trigger relay - Page 1
Forum section: electronics / beginners

author: Happyhopper
author_rank: Newbie
timestamp: August 17, 2019, 10:46:30 pm
content: Anyone know of a read relay at say 1 .v trigger?

author: ledtester
author_rank: Super Contributor
timestamp: August 17, 2019, 11:52:04 pm
content: A bipolar transistor "triggers" at 0.7V and that can be used to drive a relay.What's your ultimate goal?

author: Happyhopper
author_rank: Newbie
timestamp: August 18, 2019, 10:12:20 pm
content: To use a mp3 player as a control for a 3 volt motor thank you for your help

author: ledtester
author_rank: Super Contributor
timestamp: August 19, 2019, 01:30:41 am
content: I'm going to guess that you want to trigger a relay when the audio level is greater than a certain amount. If that's not the case you gotta give us more details on what you really trying to do.Here's a very straightforward idea:- get a LM3916 and a 555- build the standard VU-meter circuit that is described in the datasheet; there is also an instructable here:https://www.instructables.com/id/LM3915LM3916-VU-Meter/- the LM3916 VU-meter will operate from it's own supply, like +5V- wire up the 555 as a "monostable multivibrator" which will activate a 5V relay on its output;https://www.elprocus.com/monostable-multivibrator-using-555-timer/- use one of the LED outputs of the LM3916 to activate the trigger input of the 555; which one you choose will determine the trigger level

author: Audioguru again
author_rank: Regular Contributor
timestamp: August 19, 2019, 02:21:12 am
content: The LM3915 and LM3916 are obsolete, not made anymore and not in stock at Digikey.The LM3914 is still made and available only in a tiny, impossible to solder, surface mount package.

author: jeroen79
author_rank: Frequent Contributor
timestamp: August 19, 2019, 07:26:24 am
content: Quote from: Happyhopper on August 18, 2019, 10:12:20 pmCan you elaborate on this?

author: soldar
author_rank: Super Contributor
timestamp: August 19, 2019, 07:37:54 am
content: Quote from: Happyhopper on August 17, 2019, 10:46:30 pmWhy do you open several threads and so cryptic? Why don't you explain well what you want and all in one thread? Please don't waste people's time!Quote from: Happyhopper on August 17, 2019, 04:59:10 pm