46
votes
Accepted
How did smacking electron tube TVs help?
This practice is generally known as 'Percussive Maintenance'.
Any touching contacts, for instance in connectors, valves and their bases, and between the wiper of a potentiometer and the track, have a ...
- 171k
35
votes
Can I safely use a 6 A, 600 V diode in place of a 6 A, 400 V diode?
Yes, higher voltage rating is fine. It just means more safety margin against mains transients (which is good). The only difference between the -4 and the -6 is the voltage rating (see datasheet).
31
votes
Accepted
How can I cover PCB burn marks to identify burns later?
Non-reversible temperature-sensitive labels are available which will change colour irreversibly if they experience a defined temperature. These for example are 14 mm diameter which should be small ...
- 1,488
29
votes
Accepted
PCB Crack Repair
Look at the copper traces on each side of the board. Find a solder pad that each of the (on each side of the crack) gives access to the trace. Solder some 24 to 28-gauge wires to those pads that ...
- 4,116
24
votes
Can I safely use a 6 A, 600 V diode in place of a 6 A, 400 V diode?
Generally as the comments and answers already state it's ok to use a diode of higher voltage rating when the amp rating is sufficient. It would even be ok to have a slightly higher amp rating normally....
- 335
24
votes
Accepted
What is this spongy material?
It is some kind of soft-open-cell foam, wrapped in conductive tape, to ensure a good grounding and shielding contact between pieces. The foam may or may not have large amounts of carbon particles in ...
- 12.6k
19
votes
How did smacking electron tube TVs help?
It's worth noting that older TV's were constructed with point-to-point electronics soldered by hand, lacking a firm place for the components to be anchored to, such as this image showing the underside ...
- 1,530
18
votes
PCB Logic Board Reference Designator "E"
IEEE Std 315 suggests that you use "TP" for testpoints. The single letter "E" can be used for many things, including "circuit terminal", "electrical contact", ...
- 31.6k
17
votes
Troubleshoot a backplane
This is what I found, these tiny little copper bridges were all over the board. Problem solved, thank you for the help.
- 219
17
votes
Accepted
PCB Logic Board Reference Designator "E"
It's a pad for a flying probe test (which happens at assembly and you can see indentations from a probe or meter, if this is a production board then it's probably a flying probe test point).
Flying ...
- 87.1k
16
votes
Accepted
How to fix overly sensitive switch
Those flexible contacts are supposed to be centered on their places. These are called "tactile membrane switches", by the way.
It seems that metal switch domes were attached carelessly ...
- 13k
15
votes
Can I fix my monitor?
From the marking beside it (ZD) and its appearance, it would be a zener diode.
Zener diodes can be used as (simple) voltage regulators.
They can also be used to protect signal lines from over ...
- 73k
15
votes
Accepted
Using diode mode on my multimeter to debug circuits. A good idea?
The main reason for everything you ask can be summed up in one simple statement:
ESD Protection Diodes.
Pretty much every digital input on any chip has them. It's the voltage drop across those ...
- 56.3k
15
votes
Can I use a 250 nF instead of a 200 nF SMD ceramic capacitor?
No problem - just replace both capacitors that are next to each other, since they are both on the same differential signal pair. Anything that happens to one line in the pair, in terms of component ...
14
votes
How to best clean this sealed mechanical rotary encoder / volume knob?
By the limited information you give and the (not too great) photo, it seems it is a mechanical encoder, not an optical one.
You don't give any information about the equipment it is mounted on, but 15 ...
13
votes
Accepted
Is forcing power through a faulting board a good diagnostic tool?
It is a fairly standard technique when a node has a short circuit (low impedance) failure. The reason it is safe is that all of the current flows through the faulty device.
You do have to have some ...
- 29.4k
12
votes
Can I fix my monitor?
They are Zener Diodes in a Metal Electrode Leadless Face (MELF) package (*).
The blue paint indicates the cathode.
It is difficult to identify the characteristics of the diode if it is broken. ...
- 68.6k
12
votes
Accepted
How do I de-solder cheap proto boards without pulling pads off?
Remove the pins first, then remove the solder.
Heat and melt the solder on one pin. Pull the pin out. It may help to add solder to each pin before removing it. Once all the pins are out, go back ...
- 73k
11
votes
Accepted
What is the name and purpose of the following component?
I was wondering what is the name and purpose of the white box component ? It seems to be just a wire with some white body around. Is it a resistor or a fuse ?
It's a resistor, perhaps wirewound.
...
- 18.3k
11
votes
Distorted Oscilloscope Trace
Check if the unwanted waveform is 50/60/100/120Hz.
If this is the case, suspect a huge ripple on the power supply of a specific stage, perhaps due to a dry electrolytic capacitor.
If it is in the 20-...
- 80.3k
11
votes
PCB Crack Repair
If by "repair" you mean broken traces then if it's a 2-layer board, get a fiberglass burnishing pen and rub off the solder mask around the breaks in traces so you can solder to reconnect ...
- 57k
11
votes
Accepted
Disconnect vertical tab connector from PCB
Those are commonly called Faston(tm), quick-connect, or tab connectors.
They often require significant force to remove (unless you want them to stay connected, in which case they will fall off).
If a ...
- 60.2k
11
votes
How do I de-solder cheap proto boards without pulling pads off?
You don't need tons off flux. If you do it right, the pin header can be de-soldered pretty easily. You can try this method.
Apply some flux on the pins
Apply solder on a thick copper wire or a bundle ...
- 1,271
10
votes
How can I cover PCB burn marks to identify burns later?
You could use a blob of wax on the components that you suspect are getting hot to see if it deforms due to the high temperature. Waxes come in many different melting points. For example, beeswax melts ...
- 5,616
10
votes
Accepted
Why do the television manufacturers (Samsung, Sony, LG, so on) exceed the voltage capacity on LED strips (backlight) on TVs?
Isn't 133V the open-circuit voltage? When LEDs are working, voltage should be lower.
LEDs are driven by constant current sources, it's far better than using voltage regulation, because LEDs have ...
- 3,492
10
votes
Accepted
How can a marginal connection become "good" by just applying a little more voltage?
Congratulations, you've rediscovered the surprising electrical properties of a loose connection, which have historically played a major role in radio engineering.
In the 1900s, this phenomenon was ...
- 7,267
10
votes
Can I use a 250 nF instead of a 200 nF SMD ceramic capacitor?
The allowed range of AC coupling capacitance is specified by the PCI Express Base Specification:
For PCIe 1.0, the range is 75-500nF as per PCI Express Base Specification Revision 1.0 (29th April ...
- 10.9k
9
votes
How did smacking electron tube TVs help?
Bad connections, corroded vacuum tube sockets making poor contact, cold solder joints and so on could sometimes be temporarily mitigated by the judicious application of 'percussive maintenance' ...
9
votes
Mitutoyo LCD repair
Figure 1. An LCD connector. Units are cm. Look closely for the stripes in the middle layer. Source: Elastomeric Connector.
The elastomer strip is known as a "zebra strip". It has a sandwich ...
- 178k
Only top scored, non community-wiki answers of a minimum length are eligible