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0
votes
1answer
43 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
106 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
105 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
vote
1answer
36 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
129 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
43 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
108 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
109 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
143 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
47 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
156 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 ...
1
vote
1answer
84 views

ATTiny85 wont turn on, not sure how to debug

The ATTiny85 in the below circuit refuses to do anything. ...
0
votes
0answers
147 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
vote
1answer
92 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 ...
-3
votes
1answer
78 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
479 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
148 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
748 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
149 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
votes
2answers
124 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 ...
-1
votes
2answers
97 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
1k 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
271 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
votes
2answers
688 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
137 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 ...
0
votes
0answers
142 views

L7805 Not Outputting Current from Solar Panel

This question goes with a question I had a week or so ago here if anyone is interested. L7805C/L7812C Voltage Regulator with 22V Solar Panel Not Outputting a Constant Voltage Anyway, here are the ...
1
vote
0answers
357 views

L7805C/L7812C Voltage Regulator with 22V Solar Panel Not Outputting a Constant Voltage

First, here is my solar panel: http://www.amazon.com/Instapark%C2%AE-Black-Mono-crystalline-Charge-Controller/dp/B005LR9IOG And the regulator: ...
3
votes
2answers
236 views

Oscilloscope sweeps only once with DC sources and shows nothing on GND setting

I got an old CRT oscilloscope someone had laying around unused in his garage (an ATAIO AI 751A which seems pretty obscure, not getting any meaningful Google results). Unfortunately the user manual is ...
2
votes
2answers
403 views

Arduino: Only reads serial input when Serial Monitor is open. Fails when it's closed

I feel like maybe I'm having a brainfart, but I've been searching around a lot. Setup: I have a Python script using pySerial that connects to the device and writes a line to the serial port @ 4800. ...
6
votes
6answers
631 views

How do I find a short in an unpopulated 4-layer PCB?

I have a 4-layer PCB, designed in Eagle CAD 6.5. The stack-up is: Signal GND (ground) DVDD (digital power) Signal GND and DVDD are solid planes, with vias connecting them to layers 1 and 4. I ...
3
votes
1answer
531 views

ATtiny45 Timer1 clock misconfiguration

I am overlooking something with a very simple program for my ATtiny45. A program that divides the 16MHz system clock by 16 and outputs that on pin 5 (OC0A) using Timer0 and on pin 6 (OC1A) using ...
3
votes
0answers
91 views

Horrible noise after plugins power to my laptop plugged into effects chain [closed]

I'm using some stompbox effects with my guitar. I'm comparing them with my laptop where I have few VST effects. Everything sound clearly until I plugged power supply to the laptop. Then horrible noise ...
1
vote
1answer
189 views

Omron G5V-2 relay NO pins not working

I could swear that it was working for a while. I got back to my desk, tried it again, and it's no longer working. Could I have fried the NO pins on both sides? This is a DPDT relay. Everything works ...
4
votes
4answers
5k views

How do I check a BJT transistor if it is still functional?

Is there a simple method to do a sanity check on a bipolar junction transistor whether it is still functional or defective? simulate this circuit – Schematic created using CircuitLab Say ...
4
votes
1answer
830 views

Switching Boost Converter only works while probing with o'scope?

/See Edit below/: Why was the collector drive current not sufficient? I'm trying to improve a 4S LiPo (14.4V nominal) to 19V/3.5A boost converter based on the MC34063 PWM switch controller. I ...
2
votes
2answers
341 views

How can I improve my Freq to Voltage circuit?

I had a term project which was based around Analog-to-Digital convertors. We used anLM2907 Freq-toVoltage convertor to take a 150mVpp sine wave (0- 1kHz) and convert that to a voltage. The voltage ...
4
votes
1answer
684 views

FM Transmitter Circuit

I'm trying to make a FM transmitter work properly. I built the following circuit : I can synchronize with 94.8Mhz channel on any FM radio, I know that because the original sound from that radio is ...
2
votes
2answers
1k views

Setting up an ATtiny45 as I2C master - SCL toggles low, but refuses to toggle high

Another pin, another question: However closely related to Setting up an ATtiny45 as I2C master - SDA stuck low this is different question. I'm trying to control a DAC from an ATtiny45, but somehow ...
2
votes
1answer
752 views

Setting up an ATtiny45 as I2C master - SDA stuck low

I'm trying to control a DAC from an ATtiny45, but somehow the SDA line is stuck low. To find the problem in the code I did the following: I simplified the circuit to only the controller with the ...
2
votes
2answers
205 views

Why doesn't this (adapted) circuit work with the given power voltage?

I'm helping a little friend with his first project: an electronic dice from Velleman. The circuit is here (click to enlarge): He built it, I checked and improved it, everything was okay - except we ...
2
votes
2answers
3k views

Troubleshooting UPS failure

My wife said her office had an old UPS that was being scraped because it wasn't working. I picked it up and plugged it in and nothing happened. No lights, no warnings, nothing. It's a small ...
-3
votes
3answers
151 views

Troubleshooting embedded system [closed]

I am in process of troubleshooting an embedded system.It has a 3.0V DC bus line. Accidentally I connected a 12V bench supply..after that the embedded system doesn't seem to be working at all. The unit ...
4
votes
1answer
1k views

Resistor in series with primary side of transformer failing

I was given a Trio CS 1554 Analog oscilloscope. It hasn't been turned on for at least 2 years, but probably a whole lot more. Today I plugged it in and it turned on. It was usable for approximately ...
3
votes
1answer
1k views

How to stop a switched current affecting an IC?

I have 10 circuits each consisting of a Touch IC (Atmel at42qt1010) and electrode, and 2 x 350mA Constant current regulators (NSI50350AST3G) and LED's. All connected to a Arduino Mega, by ~1 meter ...
1
vote
2answers
181 views

Can a pogo pin spring cause an inductive spike?

I have an IO pin on a LM3S1751 microcontroller tied to a pogo pin which shunts to ground when engaged. There is a 100k external pullup on the pin. The pin sees 3.3V when not engaged and 0V when ...
1
vote
1answer
118 views

How do I troubleshoot a broken SAA3004 Remote control transmitter used in a remote control?

I'd like to troubleshoot and fix a broken remote control for a Guldmann ceiling lift that uses the SAA3004 remote control transmitter (documentation below in link). Can someone explain the tools ...
2
votes
2answers
544 views

Weird failure: Loud Sweep Tone on SMPS, ideas?

my brother has an old mac computer that didnt work, so he asked me to fix it, its one of those macs from the early 90s, a Macintosh Classic II. So i opened it up and i found electrolyte all over the ...
5
votes
2answers
2k views

Isolation transformer and scope when troubleshooting SMPS

I have a simple question, when troubleshooting a SMPS is highly adviced to use an Isolation transformer. But my question is this, if im using a scope to troubleshoot the "hot" side of my SMPS, both ...
3
votes
2answers
807 views

Why did my FM transmitter mysteriously die?

I made a little FM transmitter project a few months ago. I used an Arduino, a litle 4-digit serial LED display, a couple of buttons and an FM transmitter component with breakout board I had this put ...
2
votes
1answer
278 views

Help Troubleshooting This Circuit

This is a follow up to an earlier post I made here. Below is the relevant portion of the schematic for this issue (stuff to the left of Y1 is in original post if necessary). I have finally gotten ...