Questions tagged [troubleshooting]

For questions about troubleshooting circuits. Please note that repair questions must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired.

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2answers
73 views

Need help with circuit troubleshooting, Red LED constantly lights up

I have problem with the following circuit below. The Red LED is constantly lighting up, but I cannot figure out why. For the LM339, the voltage readings I get are as below. Shouldnt Out1, Out3 and ...
2
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0answers
38 views

Need help troubleshooting Teensy 3.6 SPI to DAC8568

running out of things to check with this problem I'm having. I designed a board around the Teensy 3.6 microprocessor, and I wanted to connect a DAC8568 chip to it for some analog outputs. It works ...
0
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1answer
53 views

DC voltmeter gives unknown reading when powered

I just bought a DC 3 wired voltmeter and it was working perfectly. Here is it image: I used the yellow wire for measuring the voltages. But for some reason, I desoldered the wires and soldered pin ...
1
vote
2answers
73 views

Confirm transformer fault vs markings / spec

I'm trying to troubleshoot a German ceramics kiln controller from about 1989. There is a 100ma glass fuse in front of this PCB transformer that blows after a second or two when power is applied. ...
1
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2answers
71 views

Chua's circuit producing unexpected waves?

I have built the Chua's circuit in the following diagram: I then hook it to a soundcard oscilloscope. It produces the following wave: Such waves doesn't change no matter how many times I repeated ...
0
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0answers
52 views

Chua's circuit's pattern not fully shown

I have made a Chua's circuit, and hooked a soundcard oscilloscope to it, to measure the voltage across C1 and C2. Circuit diagram: Source:Kennedy 92(pdf). Software used: soundcard scope. The ...
0
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0answers
35 views

USB detected, no communication

I had a device come with no USB cable. Since it used a proprietary USB connector on the device side, I decided to solder a male USB A cable directly on the motherboard pins. The USB device is ...
0
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1answer
75 views

Strategies for troubleshooting buck converter

I'm trying to troubleshoot a tps65261rhbr triple synchronous buck converter from 12V producing 1.8V, 3.3V and 5V. The 3.3V and 1.8V are stable and well-functioning but the 5V is not. An oscilloscope ...
0
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1answer
102 views

Why the DC voltmeter does not read zero when it measures an AC signal?(Chua's circuit) [duplicate]

I have made a Chua's circuit that is nearly the same as the one in Kennedy 92(pdf). I don't have an oscilloscope yet, so I connect a DC voltmeter at the place where probes of oscilloscopes should be ...
1
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2answers
96 views

Help With Buffer Amplifier/Filter Type Circuit

I’m having trouble with a circuit I designed and I would be greatly appreciative if I can get some help here. The circuit I designed is a buffer amplifier type design intended to take two channels of ...
0
votes
1answer
59 views

How to check (6 pin) PCI-E power rail on a pc powersupply?

Could anyone tell me if and how i might verify whether or not a PCI-Express 6 pin power lead on a PC is outputting correct voltage(s) ? A while back, I decided to try to refurbish a graphics card ...
2
votes
1answer
60 views

Current monitor circuit not working

For part of a project, I am needing to monitor the current draw of 4 low power loads simultaneously. I like experimenting with circuits and I found one online in a TI application note (AN-31 page 35) ...
0
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0answers
127 views

Wemos D1 mini doesn't boot with common ground with PZEM-004t

I'm experimenting with Wemos D1 mini and PZEM-004t to monitor my home electricity, but I'm having a strange issue. I'm trying to supply PZEM-004t independently from a Wemos with a dedicated AC/DC 5V/0....
0
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0answers
48 views

HJS-480-0-24 Power Supply begins smelling like burning plastic after 30 seconds of running

I recently purchased a HJS-480-0-24 power supply off Banggood and I tested it out by running a 150 watt heater. After 30 seconds the power supply began to smell like burning plastic, so I immediately ...
0
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0answers
69 views

Tesla Coil / Slayer Exciter won't work

I need some help with troubleshooting a slayer exciter circuit or coils. I was following this youtube tutorial and doublechecked all the connections. The power supply I use is 12V 1.5A. My secondary ...
0
votes
1answer
61 views

tube amp - high power supply voltage ?! troubleshooting

So I started working with troubleshooting a channel imbalance on the schematic attached, 12ax7 + 6L6GC push pull. But the problem seems to be a bit different... My voltages seem to be a bit hot!! (a ...
0
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2answers
126 views

Constant flickering of TFT Display

We have an issue with our TFT display. The display constantly flickers while displaying. What are common causes for flickering in this type of display? How can we resolve this issue? It's a 3.5 inch ...
1
vote
1answer
39 views

Power button behaving as OFF-(ON) momentary switch rather than latching- Troubleshooting

I have a device which doesn't turn on normally when you press the power button like it did before. You have to keep holding it down for it to remain on. As soon as you let go, it turns back off. In ...
0
votes
1answer
71 views

Turnigy servo motor needs push to start

I currently have an inspection robot deployed in a remote part of Africa that has a failing Turnigy TGY-6114MD servo. The issue started happening during normal operation and was working fine ...
0
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0answers
57 views

EMG signal from MyoWare board - sudden increase in output voltage

I am using the MyoWare muscle sensor from Advancer Technologies (this one) to obtain EMG signals from my forearm. I want to use it in a project where I will be checking if the muscle is flexed or not. ...
2
votes
2answers
43 views

LMR33630A, my built circuit doesn't match the expected output

Using TI's "power designer", I've taken their 33630A and designed it for a 5v output. My actual circuit has a slightly different value for the divider to raise the voltage up to about 5.2v, otherwise ...
0
votes
1answer
112 views

Avoid fire on a battery-powered device [closed]

I was trying to repair a battery-powered electric razor when I suspect there was a short-circuit. The device started heating and it began smoking a bit so I took it and put it in a bowl full of water....
0
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0answers
34 views

What are some techniques to troubleshoot a second order sigma delta loop?

I have designed a slightly modified second order (3-bit) multi-bit incremental sigma delta modulator (IDSM) in simulink (system level). The SNR that I get is 45dB, which is not as expected. But ...
0
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2answers
275 views

Strange behavior of the DALI controlled luminaires

I faced a strange behavior of a DALI controlled LED luminaires circuit. I have 48 LED luimianires with a MeanWell ELG150-C700-DA drivers connaected according to the scheme below: I commissioned the ...
3
votes
2answers
374 views

32.768 kHz Crystal Troubleshooting

I'm at my wit's end trying to get a 32.768 kHz tuning fork crystal to work and I don't know what I'm doing wrong. First, some background: I'm using a 16MHz crystal in conjunction with an Atmega 328P-...
0
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0answers
61 views

can't figure out why my micronucleus/V-USB setup doesn't work

I built a small attiny85-based board using vusb and essentially the schematic of the discontinued Sparkfun "AVR Stick" (at least on the usb/uC side; see https://www.sparkfun.com/datasheets/Widgets/AVR-...
5
votes
4answers
5k views

Is a capacitor bad when it looks like this?

Hello I am new to the electronics field. I am looking inside of one of my synthesizers and I see some capacitors (I think they are Mylar, correct me if I'm wrong) that look like this. I know it is a ...
2
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3answers
1k views

Troubleshoot a backplane

I have built a simple bus backplane from stripboard and 40-pin female headers for a computer project I am working on. When I tested the backplane to make sure that it functioned, I found that it's ...
0
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1answer
86 views

Identifying damaged, burnt out, or missing components [closed]

Is it possible to deduce the identity of damaged, burnt out, or otherwise missing components (or suitable substitutes)? For example, below is the PCB of a 2 speed electric razor I've disassembled. ...
1
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2answers
241 views

MCU overheating

INTRODUCTION I've designed a custom board featuring a SAME54N20 MCU. This is the third board I assembled but I still haven't got any to work: I didn't get the first board to connect to my PC. My ...
0
votes
1answer
80 views

Best way to locate a 4k stray resistance between 2 bus lines in a PCB?

I have a faulty PCB which is showing an unexpectedly low resistance between certain pairs of bus address lines. I'm measuring a little over 4k ohms between these bus lines, but according to the ...
19
votes
6answers
3k views

Why would a buck converter IC fail and blow up?

I have a deployed design in which we are experiencing a high (~4%) failure rate in the 12V to 5V step-down buck converter portion of the PCB. The buck converter's role in the circuit is to step down ...
1
vote
2answers
97 views

AL5802 LED-Driver works on the breadbord, but not on its (seemingly functionally identical) PCB

TL;DR: I'm working on a project that incorporates (besides other things) two AL5802 linear LED-drivers in parallel. Unfortunately, I felt balsy and had my complete PCB made in China before testing the ...
0
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2answers
721 views

Why is the MCP601 better suited than the LM833 for single supply applications?

Still not answered, please need some help. If you guys don't know the answer don't be afraid to admit it, but I want to generate discussion around potential solutions/calculations and not semantics ...
-4
votes
1answer
339 views

Tesla Coil Troubleshooting Help! [closed]

A couple weeks ago I decided to build a tesla coil and after a decent amount of research and building time the coil could only light up a light bulb. I have tried many things to fix it but all to no ...
0
votes
1answer
116 views

Overvoltage at input causes small jump at IC input pins

I have a PCB with voltage regulator (5V), op-amps, 2 multiplexers, 1 counter, several pots, caps, and resistors. I supply 9V. The voltage regulator converts it to 5V. Without connecting any ...
0
votes
0answers
451 views

How to troubleshoot a switched-mode power supply?

I am trying to repair a switched-mode power supply, but as of now I have no success. The problem can be described as following: The supply does not output any voltage whatsoever. The fuse never ...
4
votes
1answer
337 views

Observing ethernet auto-negotiation packets using oscilloscope

In an answer to one of my previous posts seen here: Verifying 802.3 auto negotiation, @Zac67 mentions that by using an oscilloscope I could observe normal and fast link pulses that are sent in order ...
0
votes
1answer
58 views

Troubleshooting an op-amp for amplifying a low voltage AC input

I am trying to amplify a low voltage AC input with a gain close to 5. It has a 0 DC offset and about 300 mV of AC amplitude, at 250 kHz. This is my first venture into electrical engineering and I’m ...
0
votes
4answers
338 views

Troubleshooting expensive potentiometer

Tl;dr tested pot and it doesn't show any variation across center pin. Is it reasonable to conclude it is the broken part? Hey everybody, so recently a coworker and I were reassembling an expensive ...
1
vote
1answer
62 views

Schmitt trigger issues… lumpy outputs and wrong switching voltages

I'm trying to implement the Schmitt trigger found in "CMOS" by J. Baker. Here's what the circuit should look like: And this is how the transistors should be dimensioned to achieve switching voltages ...
0
votes
1answer
54 views

Why is the logic probe reducing current from the power supply?

I am troubleshooting a very basic circuit using an inexpensive logic probe to check values. Typically when I use the probe I see current output go up about 7mA, which I assume is to power the sound ...
0
votes
1answer
129 views

Troubleshooting Dimmer Circuit [closed]

First off I do apologize for my ignorance, I know very little on the topic so please be patient. I have one of these that are broken http://www.smartliving.com.au/z-wave-in-line-dimmer.html Its a ...
0
votes
0answers
104 views

Next step when troubleshooting a PS/2 keyboard PCB with good cable

I received a PS/2 keyboard (TypeMatrix 2020) which was known to be broken, with some hope that I may be able to fix it. I don't have a lot of experience with electronics, but I know the very basics. ...
2
votes
1answer
177 views

Computer won't post / Beep unless Unplugged for a few hours [closed]

I'm experiencing this issue for almost a year now. It is slowly getting worse. My motherboard is Gigabyte GA-Z77X-D3H and my PSU is Corsair CX600. The source of the problem most likely has to do with ...
3
votes
1answer
312 views

Troubleshooting 4066 as a button hack

I have an Arduino project which needs to simulate a human button press on a third-party board, an 883LM garage door opener controller. The other board has its own power supply which is separate from ...
2
votes
3answers
435 views

Troubleshooting wien bridge oscillator circuit with 741 op amp

I built the standard Wien bridge oscillator circuit using the UA741CN op amp IC, however I am not getting any oscillation. I am powering this circuit with two 9V batteries. I'm using the values R1=...
0
votes
1answer
164 views

Troubleshooting noisy FET buffer for contact mic

I'm trying to follow the schematic on this page to create a preamp/impedance matcher for a balanced piezo contact mic. I've reproduced the schematic below. I've built it on a breadboard and I'm ...
3
votes
4answers
4k views

SMPS output voltage too low - what to look for?

I have an old switching power supply for HP 712/60 workstation (+5V, +3V3, +12v). It was working about ten years ago when i've last tried to boot the system, but now one of the output voltages is at ...
4
votes
1answer
466 views

Switching Voltage Regulator Problems

I'm new here, so forgive me if I breach any forum protocols in the asking of this question. I have designed a voltage regulator scheme for a guidance system on an aerial drone. All components ...