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46 votes
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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 ...
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  • 142k
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).
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31 votes
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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 ...
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  • 1,473
29 votes
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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 ...
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28 votes
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Phone disassembly: what's that part for?

It's a shield. It absorbs EM radiation by draining it to the electrical ground of the phone. They are used in order to meet emission specifications created by the FCC or similar authorities, or to ...
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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....
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  • 341
24 votes
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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 ...
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  • 12.1k
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 ...
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  • 1,390
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.
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  • 219
17 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", ...
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17 votes
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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 ...
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  • 63.7k
16 votes
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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 ...
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  • 10.7k
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 ...
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  • 58.5k
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 ...
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13 votes
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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 ...
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  • 55.5k
13 votes
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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 ...
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  • 24.4k
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. ...
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11 votes
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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. ...
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  • 16.7k
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-...
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  • 60.1k
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 ...
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  • 47.3k
10 votes
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Is it safe to clean contacts with an eraser?

It all depends on what you mean with safe. To cut it short: if what you are doing is some sort of professional work, the answer is not at all. As @Jodes said in a comment, the right thing to do is to ...
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10 votes
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Accidentally removed SMD pad

Yeah, you lifted the pad- it's missing entirely now (well, actually I see it on one end of the cap). It can be fixed by soldering the capacitor down to the remaining pad and jumpering the free end of ...
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10 votes

How can I fix these broken wires?

Match and mark Wire positions , clean old solder joints with vacuum solder sucker tool or gauze wire to absorb solder and clean out plated thru hole. Mark wire with ink for pin 1 so ensure same as ...
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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 ...
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  • 5,410
10 votes
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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 ...
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  • 3,877
9 votes

Is this TV power supply board damaged?

Those two main filter caps definitely look bad, as though the electrolyte has boiled away. I'd try replacing them next.
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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' ...
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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 ...
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  • 160k
9 votes

Are "rusty" capacitors enough to cause a computer monitor to malfunction?

Those caps look like they’re failing. Notice that the ends are bulged out - the score marks on the caps provide a relief point for them to ‘vent’. And it looks like they’re doing exactly that. That ‘...
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  • 40.6k
8 votes
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Please help me identify the SMD component in the picture (or help me fix my Wacom)

The part is connected to pin 5 of the USB connector, which is the 5V supply from USB. It is most likely to be a fuse: either a PTC resetable fuse or a non-resettable fuse. Its marking are consistent ...
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