Questions relating to electrical / electronic repair. Please ensure your questions are somewhat generic in nature so they are likely to help future visitors and not too localized to a specific piece of equipment.
14
votes
3answers
497 views
Why the arc when bonding-on during high voltage repairs?
When working on high voltage power-lines via helicopter the technician will "bond-on" with a steel wand called a hot-stick. During this process an arc is conducted from the line to the wand. Now, ...
13
votes
4answers
552 views
Wire broke off and stuck in a header
I'm working with an Arduino, and one of the stripped portions of the wire broke off at some point and managed to get pretty wedged into the 5V pin slot. Obviously, this wouldn't matter as much for a ...
11
votes
4answers
533 views
Choosing my first oscilloscope
I'd like to repair older computers, such as C64's, Atari's, Apple IIe's etc and their power supplies. I have a multimeter already but I'd like to get an oscilloscope. I've been offered an Owon ...
9
votes
3answers
416 views
Cleaning Circuits with Compressed Air
I've been arguing with a colleague whether it is a sensible solution to clean dusty PCBs with compressed air. While I think this is the best solution (nothing touches the PCB), he claimed that ...
9
votes
3answers
7k views
How do I fix an Omron d2fc-f-7n microswitch from unwanted clicks?
Omron d2fc-f-7n microswitches are used in computer mice all around, and they eventually start clicking several times per hit. AFAIK there is a flexible metal plate that wears out due to metal fatigue, ...
9
votes
2answers
2k views
Can I swap an electrolytic capacitor with one with a higher voltage?
I wish I knew more about this stuff, but alas I do not. I have a radial lead aluminum electrolytic capacitor (rated 470mF and 25v) that died on me. Can I swap it out with one rated at 35V, or do I ...
7
votes
4answers
1k views
How do I buy and test an oscilloscope?
I am looking to buy an oscilloscope that will last me a few years. Application is everything but RF: digital and analog with as wide a frequency range as possible/affordable. I would like to buy used, ...
7
votes
3answers
282 views
Sensibility and health hazards of reflowing computer PCBs in a domestic oven
This is a bit of a fringe question, SE-wise, but I think EE is the best place to ask it.
Some acquaintances of mine had a problem with their laptop - the graphics card stopped working. They've ...
5
votes
4answers
1k views
I took apart an LCD module. How do I fit it back together again?
To repair something, I had to disassemble it. Unfortunately, it had an LCD, and that used an elastomeric connector to connect to the LCD. Now I have an LCD, a PCB, and a spare elastomeric connector. I ...
5
votes
1answer
168 views
How to find a replacement for an antiquated transistor 2N2148
I need to replace a transistor in my guitar amplifier. The model number listed on the original schematic is 2N2148. It is in a TO3 package and the rest of the specs are listed here.
I am having ...
4
votes
2answers
952 views
Fixing an ATX PSU
I have an 800W ATX power supply given to me by a friend because it doesn't work any more. It's quite a beast and would set me back a considerable amount new, so I'd like to see if I can fix it.
Well, ...
4
votes
3answers
2k views
Detect damaged SMD capacitors
How can I easily find damaged SMD capacitors without removing them from the PCB? I want to repair my laptop's graphics card (ATI Mobility Radeon x300). I have done a visual inspection of the board and ...
4
votes
2answers
112 views
Testing an old Geiger tube?
I have an old Soviet personal radiation dosimeter that I broke as a kid by dropping it into water. I opened it up a while ago and the electronics in there were quite simple - mainly a ~10cm Geiger ...
4
votes
3answers
570 views
How to rebuild Ni-Cad battery pack for power tools
I have some cordless power tools which all require a certain 12V nickel-cadmium battery pack.
My battery packs are dead, but the good news is they're held together with screws, so I took them apart ...
4
votes
1answer
251 views
A good technique for removing 50-pin SMD CF/MD card slot with Hot air
I have a piece of equipment that has a CF/MD card on it. Somebody tried to force the card in and broke 2 pins off. I managed to replace the two pins temporarily, but it was kind of a hack job, but it ...
4
votes
1answer
666 views
how does a transistor behave when it's broken?
I'm trying to get a circuit to work (linistepper driver) and I suspect I may have fried the drive transistors (tip122's in this case).
Are there common behaviors of broken transistors?
does c->e ...
4
votes
1answer
266 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
125 views
Advice needed for replacing old ER3055 transistor
I have a transistor in a guitar amp with the label ER3055 that needs to be replaced. I asked about another transistor that I needed to replace in a post a few days ago here and I tried using NTE to ...
3
votes
2answers
414 views
is it possible to repair a DMM which was burned by putting the leads into 230V on a frequency-measuring setting?
There is a DMM (not a cheap one, so its worth to repair it), whose leads where put into a 230V AC socket on the frequency measuring range. The meter did "bzzzt" sound and stopped showing anything.
...
3
votes
1answer
95 views
Safely testing a DC supply with an unknown output configuration
This picture shows the connector for the DC end of a power supply I extracted from a dead HP MFD (Multi Function Device):
As you can see it consists of 4 pins in a 2x2 configuration. The sockets ...
3
votes
1answer
1k views
Fixing APC UPS buzzing noise
I have an APC UPS and one of the caps - an SIEMENS EPCOS 20uF 150V Capacitor - started making a buzzing noise.
This seems to be a AC, non-electrolytic capacitor and most local stores have it priced ...
3
votes
1answer
136 views
RFID coil - ends broke, can I resolder?
The 125kHz RFID scanner / reader device I have, has a coil like this:
NB> Don't have a good camera handy at the moment, so had to share a cropped image from Alibaba, but the pic is very close to ...
3
votes
3answers
344 views
How to diagnose and repair a radio?
A friend gave me a Marine VHF Radio Receiver which is working badly, and asked me if I can look into it and try to repair it (I'm not going to charge him).
The first time the radio is turned on, the ...
3
votes
1answer
579 views
Testing an Audio Power Amp with Paralleled Transistors
A question concerning my current repair project of an audio amp that uses big (600 W) but otherwise rather classic complementary output stages:
I assume when testing an audio power amp with 6 pairs ...
2
votes
1answer
141 views
How to find a replacement MOSFET
I have a small, dead power supply for a camera battery charger (cheap replacement, no brand name). I opened it up and discovered that one of the MOSFETs is burned out. The datasheet (in chinese) is at ...
2
votes
3answers
497 views
Repairing broken trace on commercial board
A friend has a USB flash drive on which the SMD USB connector broke off. When it broke, it pulled the pad traces off the board with the solder. We are trying to think of a way to reconnect the ...
2
votes
2answers
377 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 ...
2
votes
2answers
259 views
In this project, where does the rectifier go?
I was a backer of an early Kickstarter project, and now the project leads have dissapeared. Before they left, they offered some advice to fix some of their faulty units. Here's a picture of the ...
2
votes
2answers
196 views
Are there any dangers to consider when replacing a permanent AA NiMH battery?
The battery in my electric razor has failed to charge for several years. It does not turn on unless I leave it plugged in for 20 minutes and it turns off immediately if I unplug it. To save some ...
2
votes
4answers
1k views
Repair a burned trace on a PCB
I've got a PCB (from a multimeter) that apparently has 2 traces on the PCB burned away.
How they did it, I don't exactly know, but the traces are really gone completely.
The problem is however, that ...
2
votes
5answers
116 views
Want a Second Look Do all of these Capacitors Need to be Changed? [closed]
I pulled apart my monitor to check the capacitors and I think almost all of them need to be replaced but there are a couple I am not sure about
2
votes
0answers
214 views
Fixing a blown oscilloscope? [closed]
I recently bought an old Philips PM3340 oscilloscope from eBay.
I used it for a few minutes to look at a clock signal, and it was working fine. Then I heard a noise from inside, and saw a cloud of ...
1
vote
2answers
211 views
What is this component(pic)?
It's the one dead center of the circle that exploded. I was thinking it was either a diode or a capacitor of some kind, but I don't know how to tell its value from its markings. This picture is of a ...
1
vote
1answer
951 views
How can I repair lifted traces without a conductive pen?
I've recently lifted a trace (first time in 2 years) on a board in a PC power supply. What is the best way to repair this issue and similar issues (consumer PCBs) without something like a conductive ...
1
vote
3answers
80 views
Identifying SMT element 331K
I am trying to repair a remote from a car lock. The symptoms are that a red led is lit longer than usual after button press and no respond from car lock. It works sometimes. The battery and ...
1
vote
2answers
189 views
How to fix a broken sub connection and wire?
The wire connecting to my sub has snapped off, and it brought the metal connector piece with it.
I don't want to buy a new sub, but it looks like this is going to be hard to repair. Anyone have ...
1
vote
3answers
451 views
How to safely discharge high voltage (> 42 V) capacitors?
I have a 1200 watt PC power supply (yeah that's for a gaming rig!). Unfortunately it's failing on me after about 3 years. As the guarantee is over and I don't want to have shipping costs, I want to ...
1
vote
2answers
325 views
My inverter keeps flipping between battery/mains slowly at first, then faster. Why?
Here's the situation.
I'm possessed of an inverter purchased nearly a decade ago.
A few months ago it started to make a clicking noise of it's own volition
The repairman said he replaced the relay ...
1
vote
1answer
170 views
How do I choose the right replacement fuse for my multimeter?
I have a BK Precision 2709B Multimeter. I managed to blow the uA fuse (500mA/500V fast blow ceramic) on it. Is it an ok to replace this fuse with a 500mA/1kV fast blow ceramic fuse? What impact would ...
1
vote
1answer
109 views
Is it possible that a new transistor is not good even if a current runs through it?
I just got an NTE121 replacement transistor for an old 2N2148 that was in a guitar amp. It was the only part I replaced and now I have no sound coming from the speaker. I checked every component on ...
1
vote
2answers
493 views
Replacement Transistor for Ultrasound Cleaner
I'm trying to repair the generator board on a Sonix IV ultrasound cleaner. I need to find a replacement for a transistor (in a TO-3 package), but the manufacturer uses an in-house part id, so I'm ...
1
vote
1answer
692 views
Repairing a digital multimeter?
don't know if this is the right place to ask such a question but i'll try.
I opened up my DMM to check fuses. Now I would like to close it but before I can do this I have to put in the right place the ...
1
vote
1answer
478 views
220VDC motor slow and jerking
I'm troubleshooting issue of a motor from a washing machine I bought from a garage sales. Based on the service manual, I'm suppose to replace the motor assembly. So I decided to take a closer look at ...
1
vote
2answers
587 views
Repair a ripped touchscreen cable
I have an Ampire AM800480STMQWT00 touchscreen display. In the course of testing the device, the cable for the touchscreen proper got ripped by accident.
Is it possible at all to repair the cable ...
1
vote
1answer
260 views
Programming Xilinx XC9572
Can I read and save the program from a Xilinx XC9572 and burn it to another blank DC9572? I have a Needhams EMP30 which has this device on its list. I need the adapter for the PLCC 44 pin to DIP. But ...
1
vote
2answers
291 views
Capacitor value for Mini PCI type III pins 97 & 101
On the motherboard of my old Fujitsu Siemens laptop A1650G, a capacitor (C316) burned out. It seems to be connecting pins 97 and 101 of Mini PCI type III connector, which are 5V and Ground ...
1
vote
1answer
678 views
V-control broken on old (CRT) TV-Set?
I found a TV-Set in a dumpster, and checked if it's still working.
Indeed it is somewhat functional, but the picture is distorted:
(screenshot of the TV)
Depending how bright the picture is, it ...
1
vote
1answer
194 views
Using a broken Linksys WMP54G radio
I have a Linksys WMP54G v 4.1 Wireless PCI card from an old computer I would like to use it for something but I have a problem.
The end that the antenna attaches to is broken (See picture). I was ...
0
votes
5answers
4k views
Fix remote controller button contacts
On almost every remote controller the buttons stop reacting after a while, and you end up squeezing the remote out of his life while trying to switch the channel...
I found some link where it ...
0
votes
2answers
136 views
Identify a fuse part
I'm trying to identify a fuse part that says 125V T 2A on it.
It seems to be a solid state fuse soldered in place. IE I can't just snap in another replacement fuse in a glass tube like I'm ...
