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2
votes
2answers
79 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
375 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
59 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
98 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
59 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
503 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
128 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
210 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
82 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
95 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
238 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
194 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
192 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. ...
5
votes
6answers
505 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
293 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
83 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
123 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
3k 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
636 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
211 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 ...
3
votes
1answer
598 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
755 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
576 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
180 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
1answer
2k 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
133 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
950 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
929 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
159 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
107 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
501 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
1k 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
496 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
252 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 ...
7
votes
2answers
162 views

1/2 screen on 1953 Zenith TV

I have been working on a 1953 Zenith TV; I can get raster on the top half of the screen only. If I reverse the leads on the Vertical deflection coil, I get raster on the bottom half only. So far, in ...
7
votes
2answers
2k views

Poor eye diagram, where to start looking?

I'm trying to debug a 100Mbit ethernet board and I'm running up against a problem I'm having trouble trying to resolve. This is the eye diagram for the transmit pair. The receive pair is very ...
1
vote
2answers
614 views

What other than capacitor rot could cause a capacitor to bulge and fail?

I've been teaching myself the fine art of monitor repair - replacing capacitors on a trio of lcd screens. Apparently they all had capacitors that had suffered from the plague - though a mild case of ...
7
votes
2answers
218 views

How do i test capacitors?

I've just gotten through replacing capacitors on a trio of dead LCD screens (nothing's blown up yet, so far) - they either had one or two capacitors on their inverter circuit SLIGHTLY bloated, and not ...
6
votes
3answers
9k views

How to find a faulty LED in a LED Christmas lights string

I have a LED Christmas lights string, which consists of two circuits of LEDs connected serially. It is working directly on 110V AC. Most LED sockets have 2 wires connected to them, some have three. ...
7
votes
3answers
3k views

Why is SMPS controller IC failing?

I'm back to diagnosing power supply failures, in an LLC resonant SMPS based on the L6598, from a 400 V PFC supply with ostensibly 400 W output. I'm new to SMPS, and learning this all as I go, and the ...
9
votes
4answers
4k views

Find short location on PCB

I am trying to find a short on my board. So far, I have used my fluke to measure the resistance to gain some clues but everywhere I measure 4 ohm, so that didn't work. I am thinking of trying to ...
2
votes
1answer
293 views

How to identify shorts on IC's

I've been trying to solder an SSOP 0.1" onto sparkfun's breakout board. However Somehow I've managed to short a positive to ground. Are there any tips you can give me in identifying it? I'm quite ...
3
votes
4answers
3k views

Arduino serial communication fails when stalling/loading a DC motor controlled by PWM

I'm using the following circuit (from http://luckylarry.co.uk/arduino-projects/arduino-control-a-dc-motor-with-potentiometer-and-multiple-power-supplies/) to control the speed of a 6V DC motor powered ...
3
votes
1answer
151 views

Sharp Distance Sensor

I have a Sharp GP2D120 which is a distance sensor for the range 40mm-300mm. Reading the datasheet the output voltage should change from quite high to very low. I cannot get this change to happen. The ...
1
vote
1answer
200 views

Power brick with a high pitched whine

The powerbrick for my computer emits a high pitched whine. What could be causing the noise? Any way I can stop or reduce it?
4
votes
5answers
534 views

Troubleshooting a broken speaker system

First I apologize if this is the wrong place for this question. Recently my sub-woofer/amplifier stopped working, and I would like to know what is broken. I opened the case and didn't find any ...