Quote from: Jazz P Bass on August 06, 2021, 12:08:21 AM
Ohms Law
I=P/V
375W /120V = 3.12Amps

What you should look for is a cord that is the proper length for how you plan to use the amp.

At home a 5 or 6 ft cord will be fine.

On a stage you may want a 10 footer.

Also, it's a good choice to get a short power cable and a longer IEC13-to-IEC14 extension cable.

Then you can make sure that the power cable is able to be short enough to eliminate mess in domestic condition and long enough to reach the outlet on the stage.

Also we can use lazer printers to print the toner onto a piece of "heat-transfer paper" which is, technically, the "oily" bottom layer of stickers. Print on the oily side, use a clothing iron at 200 degree centigrade without steam to melt the toner to the copper-plated raw boards, cool it down, peel the paper away, and throw the board into the solution of iron chloride.

It's never too frequently to say that everyone should ALWAYS BE RESPONSIBLE TO YOURSELF and THINK TWICE before doing anything at your workbench. NONE of the safety measures can protect you from being ZAPPED TO DEATH if you actively rely on them and ignore basic safety principles.

High voltage kills, but you can't see'em with bare eyes. Thus, always keep a neon tester within your reach and use it to confirm the circuit is not at a deadly voltage before touching it.

Capacitors are, kinda, like bee stingers or snake fangs, still able to give you a painful stab after de-energized (even for a long while sometimes!) There're normally powerful capacitors between power rails, so NEVER touch a circuit immediately after it's unplugged from the mains. Wait for at least a minute, and then short the rails to ground before working on the circuit.

While working on powered circuits, e.g. adjusting the bias of a head, ALWAYS insulate yourself from the ground. Use a chair with non-metal legs, put your feet on a thick piece of wood or styrofoam panel, and avoid touching the walls. Also, use an isolation transformer to power your circuit so that you won't get zapped while touching a single point of it. Connect a momentary footswitch in the circuit before the transformer and make sure the current is only on while stepping on the switch. By doing this, the power will immediately be cut off while you're leaving the workbench or you're zapped.

However, while working on low-voltage solid-state systems, things will be totally different - In this case, you'll have to get yourself grounded to prevent any static discharge to the delicate FET-based chips and consequently fry'em. An antistatic wristband would work well - Connect it to a safe grounding point like a piece of metal water tubing. Do not connect it to the ground pin of a power outlet or to the grounding of a lightning rod, as that'll electrocute you while something is having a power leakage or while there's a thunderstorm. Talking about thunderstorms, try to avoid electrical working in them.

That'll work well. Actually, any IEC power cables would work equally well for home and information products. Always use cords with a wire gauge of 0.75mm² or greater(I dunno how much AWGs it equals to ... In my country, we use squared millimeters instead of AWGs to measure wire gauge ) to ensure an abundant supply of current and to eliminate risks of fire.

Quote from: teemuk on November 19, 2011, 10:41:34 AM
Someone also instigated a rebellious act to sell those light bulbs as "heat balls" ...or something in that manner. Really a genious idea to get around the loopholes.

I'm all for protecting environment and saving energy but I don't support total ban of something that in the end is just a drop in the ocean when considering the big picture. The electricity consumed by my house's light bulbs is peanuts compared to street lights not to mention some industrial plants that alone may draw as much as electricity as mid-sized towns.

I couldn't agree with you more. Compared with illegalizing incandescent tungsten bulbs, why don't ban the over-updating of intelligent products like phones and computers? New models of phones and laptops continuously fountain up in electronics shops and lots of old(but still well-performing and even powerful!!!) ones floods down to trashcans and landfills. Huge enterprises like Apple ban the re-using of second-hand IT products by blocking kernel authorizations(like jailbreaking and rooting) and applying activation locks intentionally.  That trashes many tons of chips which need huge amount of energy to produce.

Also, when it comes to so-called energy-saving illumination devices, do they really cost less energy and cause less pollution than traditional ones? Mentioning that some companies intentionally overloads LED elements in order to limit their lifespan and therefore to force customers to replace elements more frequently, it really drives me crazy. That's the REAL CRIME TO THE EARTH, even more guilty than producing tungsten bulbs.

Quote from: g1 on June 06, 2021, 03:06:57 PM
I was wondering the same thing.  Image search couldn't find it.
But searching the name 'jiangchengdianqi' came up with this:
https://item.taobao.com/item.htm?id=640352366664&ali_trackid=2:mm_35034521_1365150179_110185350026:1623006068_299_1403283794&union_lens=lensId:MAPI@1623005665@2106c1d5_0842_179e2ad1a0b_97ca@01;recoveryid:1623006068_299_1403283794&pvid=100_11.229.250.111_75062_5841623005665736351&ak=28580521&scm=null&bxsign=tbkKZ3DH41tDAmbZch0LDRimB4X+3jr4PZun2KcrKwVzZST0LXPw3/Kq+NERoNL84IAhYxeDN7JPfM2ZnD2sEznYCyUrv/MY22EwiSQscXTT/s=

It leads to the correct link of the product. However, that's sold on a Chinese e-commerce site called Taobao. I'm not sure if you can get access to it from other countries.

Quote from: RC cola on September 17, 2011, 07:16:38 PM
Overhead cranes with a ride on operator has this foot switch better known as the "dead man" switch.

Haha......Railway locomotives also have similar designs. German locomotives are usually equipped with dead-man detectors called the SIFA system or the PZB system, while Japanese ones have trigger-like buttons at the back of the throttle/braking handle that'll immediately smash the brakes while released.

Uh...I ignored this point... The lightbulb can be considered as a PTC thermo-resistor... uh-oh. Thanks for your correction.

Seems like there's already commercialized version of "lightbulb limiter" with built-in multi-parameter (voltage, current, power, cos-φ, energy consumption and mains frequency) electrical meter and a GFCI-protected outlet...
Kinda fun to see a lightbulb socket on this factory-made version haha. I anticipated that it'd use a power resistor instead, but...lol

toast resistors, fried amps, fused relays......Why're geeks always speaking so FuNnY?
In my opinion the problem might be caused by neutral wire breakdown in the club , which could lead to a 380-volt high voltage on mains.
It's tragic but, even switching power supply modules can't handle such a CRAPPY voltage so always use a surge protecting extension cord

Quoting from Youtuber ElectroBoom, you need a FULL BRIDGE RECTIFIER!......no, a single puny diode (1n4007) would be ok.

As for signal generator, a cheap MP3 player with several WAV files inside(100hz sine wave, 1khz sine wave, 12000hz sine wave, 10hz to 24000 hz sweep, white noise, pink noise) is a pretty good choice. Smartphones with portable DAW software like Garage Band, Caustic 3 or FL Studio Mobile are much better choices.

Hi there!
I'm keen to help you but ...... It seems that the information you offer is a little bit limited.
First, you can try using a 3.5mm TS to 6.35mm TS audio cable to feed line-level sine wave into FX return jack. If the sound is distorted, the problem is in the power amplification section.
If it's not distorted, then the power section is OK. Check if the lead channel works as common to probe out whether the problem is only on the clean channel or not.
If the lead channel is also broken, then the problem might be at the input stage(probably the feedback resistors are not well soldered )Otherwise, it is out of my range of ability and I must apologize that I'm unable to help you further.

If your amp has 2x8ohm speaker outputs which are paralleled, it will be certainly OK to use 4ohm load. However, it'll be dangerous to use 4 ohm load on amplifiers which have only ONE 8ohm output-The current going thru the transistors will be doubled and they'll overheat and, plausibly, burn themselves down under such a current while using original cooling systems so using larger heat sinks and adding fans might be the first thing essential to be done. Replacing a transformer may help to prevent overloading and burning among the area with mains voltage but NEVER use any transformers with higher output voltages. Use ones with the same voltage and higher output current instead. In addition, don't forget to check the rectifier circuit and the fuse to prevent potential overloading.

For safety reasons, a hold-down type pedal switch(It activates while you press it down and deactivates as soon as you release it) might be connected in series with the powerboard and then, while you're zapped, you release your feet and then the power goes off and it saves your life. Good gadget.