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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3answers
82 views

Troubleshooting LTC4150

Earlier today i changed the value of the shunt resistor of my LTC4150 coulomb counter from 0.05 ohm to 0.5 ohm to get more precise readings.In the datasheet it was specified that voltage drop of the ...
1
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1answer
45 views

Effect on opamp lead length for non-functional wien bridge oscillator

I've built two diode stabilised variable frequency wien bridge oscillator circuits according to this schematic: (source). Both are on the same stripboard and connect to a single LM324. One of the ...
1
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1answer
71 views

Voltage spikes with ZVS full bridge

I am designing a DC/DC converter. I chose the fullbridge topology. The requirements are as follows: Vin = 75 - 125 Vdc Vout = 200V P = 600W Fs = 100 Khz The basic schematic is as follows: I use ...
5
votes
2answers
145 views

Debugging an MCU short circuit

I have a board with an STM32F103VGT6 MCU. Yesterday, the MCU worked fine, I had just gotten semihosting working, LED blinking, played around getting a timer running and so on. I then decided to try ...
0
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1answer
70 views

Wien bridge oscillator circuit doesn't work

I've connected the circuit of Fig 3.4.6 in this link which is shown below: Here is the circuit that I've connected: Where in my circuit: R3 = 100 kOhm R4 = 47 kOhm R1 = R2 = 5.1 kOhm C1 = C2 =...
1
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0answers
63 views

Troubleshooting Assembled PCB

I designed & assembled 3 copies of a circuit (BNO055 motion sensor board, used recommended i2c application from the datasheet). 1st one had some soldering issues, fixed them and it worked, ...
1
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2answers
106 views

The leads of my 3-phase motor are incorrectly labeled. How do I determine the correct labels?

I connected my new-in-box 3-phase motor to my new-in-box VFD, following the instructions in both manuals and the wiring diagram on the name plate (low voltage configuration). With the power off, ...
0
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1answer
42 views

NOR Gate is Working Correctly with Vcc Pin Disconnected

I modified my Sega Master System to have a pause button on the actual controller. To process the signal, I soldered a quad NOR gate to the I/O and CPU circuits in the console. The idea is that the ...
0
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2answers
169 views

Can I replace FP50N06 with IRFZ44N?

I own a car audio amplifier which uses a DC to DC converter having a MOSFET of the type of FP50N06. However, after prolonged use, the three of the positive rail switching MOSFET cooked and smoked. I ...
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votes
1answer
129 views

Why did my LED burn up? [closed]

My circuit was basically a push button hooked at 5 volts with a 100 ohm resistor. The push-button was directly below the LED. Why did it burn? Why didn't the resistor work properly? As you can tell by ...
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1answer
71 views

Help with son's 18 V car [closed]

I need help with the wiring on my son's car. I'm trying to run 2 x front and 2 x rear #QG550 12 V 45rmp motors using independent 18 V power supplies, 18 V front and 18 V rear. I wish to keep the ...
1
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0answers
167 views

Oscilloscopes - Comparing Traces

I'm new to Oscilloscopes and so this question may be a simple one. We have a Rigol DS1104Z Oscilloscope and would like to compare the same point in the circuit at different times as the voltage ...
1
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1answer
297 views

What is causing a loud static POP when PTT mic is keyed?

Hi folks! I have been investigating this static POP noise problem for a while now, including talking to the sound shop I bought the amp from and consulting with the manufacturer of the amp. I am ...
1
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2answers
52 views

PCB outdoor moisture effect and protection

I have been working on a project that requires me to place a pcb outdoor for days to collect data. It has been done 3 times already, and all have failed with unknown reasons. First I thought my ...
1
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2answers
59 views

Soft-on/off circuit turns on on startup despite being jumpered to stay off, why?

So, I am building the soft-on/off circuit shown below and described here on a breadboard to test it out before I actually put it into a design. However, to better fit the parts on hand, I decided ...
1
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1answer
106 views

Will this phototransistor circuit work?

I'm building an 8 stage coil gun for a physics project, and I want to verify this circuit as I've never used a phototransistor before and I'm still pretty new to mosfets. Here is a schematic: The ...
0
votes
1answer
36 views

vibration activated delay ciruit

why this circuit doesn't work? I need this circuit to sense vibration, then after some delay, turn on the piezo beeper, and then after some delay, turn it off. Q1 is turned on when vibration is ...
2
votes
1answer
94 views

How can I troubleshoot stuck/flipped bits in a serial connection?

I'm working on reverse engineering some scrap vaccuum fluorescent displays from Noritake that lived their previous lives inside a payphone. No datasheet exists for it since it's a custom part; ...
0
votes
1answer
255 views

Strange output from an AD595 in single supply mode

device under test I've got a K-type thermocouple wired up through an AD595AQ to an Arduino in single-supply mode (12VDC to pin 11), with the addition of an RC filter across the thermocouple inputs (...
2
votes
1answer
345 views

Faulty relay(s), capacitor or power source? [closed]

I have this IKEA Bekant Sit/Stand electrical desk and all of the sudden today, it won't work properly. I push it to go up or down and it goes for a little bit and then stops. I can hear well the ...
0
votes
1answer
101 views

Troubleshooting 16x4 LCD Display Showing No Output

I have a 16x4 LCD (model DCM16433) that I suspect is dead. It has 14 pins rather than 16, but this should just mean no backlight. I have hooked pin 1 to Vss, pin 2 to +5 V, and pin 3 to a 10k pot, but ...
0
votes
1answer
66 views

Toubleshooting PCB circuit - strange Zener diode behaviour

I have two units of a device which I shall call deviceA and deviceB. DeviceB is malfunctioning. Therefore I compared the resistance values of the same components on the boards of both deviceA and ...
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4answers
125 views

Explantation for fried charger with Multimeter

I have a 9v AC to DC wall adapter that I use to power my Arduino boards. The label says it gives 9v at 1000ma but I wanted to test the validity of the label to troubleshoot. When I connected my ...
2
votes
2answers
2k views

transformer has continuity but no voltage output?

I have two old transformers that appear to be fine, however no DC voltage was measured on the secondary coil. I have measured: The input voltage: 229 AC the input coil ohms: 0.015 kOhms the two ...
0
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2answers
34 views

Troubleshooting stepper motor drivers

I repair intelligent lighting fixtures. These devices have a large number of motors, and so they also have a large number of motor drivers. It's not uncommon to have a single PCB with more than a ...
0
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1answer
57 views

Tracking a circuit path across a crack?

I am new to the world of electronic repair. I have connected several wires to this board and have been successful in getting the paths across the crack to connect. Is there an easy way to trace out ...
1
vote
1answer
128 views

Burning out relays when supposed to be within ratings

I am using this Normally Closed Relay on a 24V circuit: DataSheet The circuit is 24VDC source, which I measured the Amperage in series to be 29mA at the highest. I've breadboarded a lower voltage ...
0
votes
2answers
203 views

What is causing this step-up converter circuit to fail when introducing a transistor?

I built three separate circuits with the intention of making a colored led cycling solar sun jar. Each circuit works on its own. With just the RGB ATtiny85 circuit it works with 3x 1.2 volt AA NiMH ...
1
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1answer
155 views

Z80 control pins not reading a defined logic level

I'm having trouble getting my simple Z80 based project to work. I asked for help here last week, and received an excellent response on troubleshooting the Z80; here is the relevant part: There ...
2
votes
2answers
210 views

My Chua's Circuit is flatlining (i.e., malfunctioning)

I tried to build a Chua Circuit, but it doesn't appear to be working as expected. The problem is that, while it's supposed to be an oscillatory circuit, I see no oscillations. Refering to the diagram ...
0
votes
1answer
216 views

Z80 Simple Computer Troubleshooting: IORQ pin not going low

I'm following the instructions at http://www.reocities.com/SiliconValley/2072/z80proj1.htm to build a "proof of concept" Z80-based computer. I have wired everything on my breadboard, and programmed ...
3
votes
1answer
363 views

Crystal oscillator problem

Here is the datasheet of the crystal (32 MHz) that I use for a MCU. The right layout is an older version of my board which totally works fine. The left one is the newer version where I placed the ...
1
vote
5answers
132 views

A simple voltage divider

I attended a workshop on troubleshooting and we were asked to find the flaw in the given circuit. A guy pointed out to the organizer that R3 was short ckt and R2 was open ckt. However I was pretty ...
0
votes
1answer
472 views

PWM Red LED on Stellaris Launchpad

I am trying to PWM the red LED on a Stellaris LaunchPad, following the recipe in the datasheet p.706, taking a couple shortcuts from the Stellaris® Peripheral Driver Library. I cannot figure out why ...
0
votes
1answer
53 views

can an ammeter damage zeners

So I got this small circuit that plugs to the mains as power source. as for its DC converter, it's one of those transformer-less ones that drops the voltage with a resistors and filters before ...
0
votes
3answers
353 views

Tube Screamer PCB trouble shooting?

I recently bought a tubescreamer PCB from Tonelab and soldered it together yesterday. I decided to go for Ts-9 model which requires (Ra=470ohm, Rb = 100kohm, Ca = unused) I tried to match all parts as ...
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1answer
154 views

ATTiny85 wont turn on, not sure how to debug

The ATTiny85 in the below circuit refuses to do anything. ...
1
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1answer
462 views

GPIO using StellarisWare with LM4F120H5QR LaunchPad. SW2 not working as expected

I am trying to figure out how to properly use StellarisWare, the built in ROM calls, for GPIO. The Stellaris LaunchPad has two switches (SW1, SW2) and three LEDs (RED, GREEN, BLUE). I wrote a little ...
1
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1answer
252 views

undefined reference to `ROM_SysTickIntRegister'

I am trying to program the Stellaris LaunchPad to blink the red LED at 1 Hz, driven by the sysTick interrupt. I get an error though that I've been unable to solve yet. The C source I came up with ...
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votes
1answer
165 views

Help Identify Faulty Component - Dishwasher Controller Board [closed]

Not sure if this is the right place to post this. Recently my dishwasher gave away :(. It works fine (goes through wash - rinse cycle)when empty but the moment it is loaded, the display lights go ...
1
vote
4answers
2k views

Can a current be induced in an HDMI cable that runs parallel to a 120v AC cable for 15 feet?

I just went to go unplug an HDMI cable and got shocked from the end of it! The only possible causes of this that I can think of are that the receiving or sending end of the long (50ft) HDMI cable is ...
5
votes
2answers
176 views

Ideas for troubleshooting a noise generator on a PCB

I am building an electronic "dice" that uses an ATTiny84 to sample avalanche noise from a 2N2222 in reverse-bias and generate random numbers, which are then displayed on 2 7-segment displays. When I ...
6
votes
3answers
1k views

Troubleshooting/debugging PCB

This may be an off topic question, but I'm sure many of you have the knowledge and experience to help out here. A quite complicated motherboard was flexed. The resulting symptoms include cross-talk ...
0
votes
1answer
254 views

Teensy 3.0 Problems with moderate range (~40m) OneWire Signals

I'm using a Teensy 3.0 (with its 3V TTL signaling) to try and communicate with some Dallas DS18B20 temperature probes. I'm not using parasitic power because I've heard a separate power line allows ...
0
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2answers
218 views

Multimeter question [closed]

I was trying to measure some voltage on cables going to ECU (car computer) and I had my multimeter in wrong configuration. It was set for 10 sec max 10A fused. When I touched the cables there was a ...
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2answers
205 views

Likely to fail components in amplifier board [closed]

I'm troubleshooting a car audio amplifier that has no life except for power led. I'd like to avoid having to pull it in a million pieces to find the broken component(s), so: What are the most likely ...
6
votes
2answers
2k views

My serial receiver verilog implementation does not act as expected

I have coded my own implementation of a serial receiver. It will work for incoming data at a baud rate of 115200. Here's my code: ...
0
votes
2answers
866 views

Why is my simple relay circuit only half working?

I am new to electronics and I am following the book "Make: Electronics" by Charles Platt. I have built a circuit with a 12V DC power supply, a 1K resistor, a relay, two LEDs, and a momentary-on ...
0
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2answers
2k views

Heating element as resistor for motor fan assembly in heat gun

Repairing the heat gun is not an option at this point, but out of curiosity I want to dig deeper into the problem: There are four wires associated with the heating element assembly, two of which ...
1
vote
2answers
222 views

Weird Behaviour with Bootstrapping Circuit

I'm trying to make a 3 phase BLDC driver and picked up some FAN7888s since they're inexpensive gate drives with all 3 phases on one chip. I read the relevant datasheets and application notes and ...