60hz hum

Power supplies had caps sizes that peaked out back in the mainframe computer days of the 70's and 80's. Computer and stereo power supplies do not have huge EL cap banks in them any more.

"newbies"? So, "Oldbies" do not buy such things?

I think you are a "guessbie".

Amp chassis needs a tin foil hat.

reposting

The hum is developed by the guitar and hook-up.

Check amp input sockrt ground, guitar connector cable shield and signal path and guitar socket for continuity.

Check guitar body pick-up for continuity, dry solder joints and loose wires.

RL

** So you have no idea what magnetic induction is - legg ???

Happens a lot with coils of wire wound around bits of steel.

Also got no idea how far the stray magnetic field extends from an AC supply transformer ??

EVEN WHEN YOU HAVE JUST BEEN TOLD !!!

Wot a FUCKWIT.

..... Phil

Depends what you call a ground loop and the source of the current flowing in it. Beware particularly of equipment using switch-mode power supplies which almost invariably inject a 'nasty' mains frequency related waveform into the the earth / ground ( signal return path of an unbalanced system ) and it sounds horrible.

50 / 60 Hz hum can also easily be induced into unbalanced cabling from adjacent magnetic fields such as power transformers for example which is nothing to do with ground loops.

As audio equipment gets better and better people become more discriminating about the level of hum they will tolerate. It is a subject I have studied extensively and intend to bring really good products to market to help avoid it as opposed to the 'snake oil audiophool' ultra-high priced items on sale in the hi-fi market right now aimed at the gullible.

If you want to avoid to hum run ALL your signals balanced like professionals do. The difference is startling and doesn't need silver or gold plated wire soldered by virgins at midnight at a full moon.

Graham

due to the hugely increased level of spam please make the obvious adjustment to my email address

A rather poor one.

Graham

-- due to the hugely increased level of spam please make the obvious adjustment to my email address

"Eeyore"

** On the contrary - that is the classic "ground loop hum " scenario.

Magnetic field injection is only possible where there is a loop to receive it - the cabling between items of equipment completes that loop with the same items' safety ground conductors.

Any mains transformer in the vicinity can then inject a voltage into that loop, typically of about 1mV.

If the cabling is unbalanced - you will get a 50/60 Hz hum voltage appearing at the input to the amplifier.

Proof of this that:

1. If you move the cables so as to close up the loop area, the level of the hum drops.

1. The hum itself is predominately 3rd harmonic ( ie 150Hz or 180 Hz ) which is only possible from radiated field of a mains transformer.

.... Phil

A good rule of thumb is don't touch an electric guitar and anything else (such as a microphone or mic stand) at the same time. Either one can be electified and the other grounded, and if so the path for electricity would be through you, with possibly fatal results.

That's not a ground loop, it's a lack of ground connection between the guitar and amp.

While you're at it, check out the continuity of the guitar cable with an ohmmeter. Shield-to-shield should be shorted, as well as tip to tip. Not having the ground connected will make hum as well as the amp getting very little signal from the guitar.

Have an electrician fix that outlet and test all the other outlets.

The hum that went away is electrostatic - the chassis, when not connected to ground, has some 60 Hz voltage that is capacitively coupled from the transformer primary winding.

Do you have other outlets you can plug the amp into?

The source of the remaining hum when the chassis is grounded is still unknown - if it changes wht moving the guitar around it's surely magnetic from the transformer. If it's constant it could be some electrical problem in the amplifier.

I've had an experience with that. Back when they still had nonpolarized

2-prong plugs, I had heard that turning the plug around on ONE piece of equipment would ensure that at least both of their chassis were at neutral.

Well, I was at a resort one summer, and there was this one room, like a party room, with a damp concrete floor, and there were a few other teenagers in the room, one of whom had an electric guitar and an amp.

There was some hum. I proclaimed, "Oh, just turn the plug around on the amp!" So, he did, turned it on, and I proudly, in bare feet, on a moist concrete floor, reached out and laid all four fingers across all six strings.

BZZZZOW!!!!

We all laughed, we turned the plug back around, and I was afraid to check the guitar again. ;-)

Cheers! Rich

There is no such thing as a "dry solder joint".

I think the term "bits" is sadly the wrong choice in this case.

Yes there is - it's an alternative expression for "cold solder joint."

Although, it's kind of a misnomer - I've never seen a _wet_ solder joint, or when I have, I've dried out the board. ;-)

Hope This Helps! Rich

I've heard it both ways, and I knew what you meant. When soldering a connection the flux has to "wet" the surface before the solder itself will stick "to" the surface. But "cold" is more common. I wonder how many people can see the difference nowadays between a "good" and "bad" solder job by visual inspection?? Obviously, functional testing is required for suspicious joints, micro-cracking, etc.

Absolutely NOT!

It is a well known FACT that some dopes in the industry coined this STUPID term, and NO, it has NO analogy to a cold solder joint.

A cold solder joint is a cold solder joint, and there are no other descriptions for it.

"dry solder joint" is now, and has always been a total mis-nomer, and ANYBODY that uses the term does not know about soldering.

You have NOT seen a "wet solder joint" either.

The term "wetting" used in solder operations relates to cohesive and covalent "wetting" that occurs between two very clean surfaces that have the ability to bond by valence shell or by surface intermetallics.

In RoHS operations, it is hard for even a good, seasoned inspector, unless he or she has a firm intimacy with metallurgy, and lots of experience with both inspection as well as actual creation of such joints. You have to know how to make them before you can claim to be able to inspect them.

Most today are grainy in appearance, but that is now the accepted norm.

Flux doesn't "wet". The flux de-oxidizes the surface to yield bare, fresh media. Then, the hot solder makes an intimate "wetting". It is the solder's surface tension that is the functional physical agent here.

Very true. "Wet" should not be used here. Some of my use of paste flux wicking into copper tube joints spilled over into a thread of electric wire joints using rosin core solder.

If you have any relevent points to assist the OP, feel free to make them.

RL

I did, dumbfuck. I educated the idiot that used the term improperly as well as any reader that might think that the idiot was actually using a proper term.

He was not. You are a stupid twit for making nothing but a retarded, peanut gallery comment on the content instead of actually making any form of contributory post based on the topic.

These are both common coloquial terms that describe defective solder joints common to manual and wave soldering operations for terminal-mounted or through-hole pcb-mounted components.

Dry joints are most commonly created by overheating or prolonged heat application, exhausting or burning the flux, but they can also be created by physical movement of the parts being soldered, during subsequent cooling. They are often some of the first defects experienced by the novice assembler or hobbyist.

The cold or dry joint terms may make more immediate sense to the average user than the listed 'nonwetting' or 'dewetting' terms, are more popular (see below)and actually precede them, historically, in use.

Nonwetting:a nonwetting solderability issue is when the solder does not "wet" or make a metallurgical bond with the surface you are trying to solder

Dewetting: a dewetting solderability issue is when the solder does initial "wet" and makes a metallurgical bond with the surface you are trying to solder but then puddles/retracts on that surface similar to an oil on water reaction.

The JSTD-002C, Figure 2B, page 43, has photos of dewetting and nonwetting - microsections, actually. A draft of the later revised standard is currently available:

Hope this helps.

IPC terminology may use the latter terms to describe absence of a required defined quality or quantity rather than the presence of a defect, but it's probably just style. For example, the word cold is not present anywhere in the standards - absence of heat, sub-optimal temperature or other descriptors are prefered. The word dry is only applied when refering to materials that are liquid at room temperature.

- As far a poopoolarity is concerned:

"dry solder joint" gets 175,000 web page hits when googled. "cold solder joint" gets only 14,500.

de-wetting, dewetting, non-wetting or nonwetting all find less than

75,000 hits, many of which are not used to describe a soldering process or a solder joint.

This just the way it is, Junior.

RL