TOS FANTASTIC BUT...........

[TIMBO]

Hi guys, The TOS rebuild is just about done BUT the BUZZ thing is happening again  I followed merlins grounding but i am getting the buzz again and tried a few other ways of grounding but no change. I can't believe that in two builds i am still having to battle with this  The buzz sounds the same in both builds and goes away when you touch the guitar strings (almost dead quiet at higher volume)

Things i have tried :-
Different valves
Different guitar leads
Different power outlets
Different IEC cords

VERY FRUSTRATING 

[PRR]

With power un-plugged, what is the Ohms from guitar-plug shell to IEC inlet center pin?

[The_Gaz]

Don't know about your other build, but you're saying the buzz goes away completely when you touch your strings? Does it buzz with you guitar volume down? How about with no guitar plugged in? If not, then it's not your amp.

[TIMBO]

Hi guys, PRR i get a reading of 1ohm. Gaz no buzz w/o guitar lead plugged in. I just did a few things to see what my guitar does,First my Les Paul, Bridge pup I get no buzz with tone on 0 and vol on 0, buzz with tone on 10 and vol up to 9.5 and goes away at 10 but buzz goes away with vol on 10 and tone on 0 same with neck pup. The same with the strat buzz goes away with tone on 0. Thanks


Tried another amp a VJ hot rod thinking it might only be the higher gain amps that is effected but it's the same. I got three good brand guitars and all have the same do thing, house wiring??????

[tubeswell]

... no buzz w/o guitar lead plugged in.

So no buzz without a guitar plugged in - even with amp volume up? - if that's the case, then its not grounding in your amp causing the buzz.  Its more likely to be a bad guitar cable or poor shielding in your guitar body cavity.

If your input socket is the non-grounding type, you can wire a ~.01 - .1uF cap from the input jack sleeve contact to the chassis (near the input jack). This can 'suck' cable shield noise away.

[tubenit]

Well good news is that you've eliminated a grounding problem with the amps!    

That leaves:  guitars (would be weird to have 3 guitars do this especially if they're different brands), or guitar cords, or house wiring.

And does it buzz in every outlet in your house?  Are you near any variable speed ceiling fans or adjustable slider switches for lights?

Can you take the guitar and amp to work or a friend's house in another neighborhood & try it for hum?  I say another neighborhood in case the builder for your entire neighborhood wired everything up wrong.

And of course, try other guitar cords.

With respect, Tubenit

[LooseChange]

This is a local issue. Happens at your place, in the area that you're setup.

I have a buzz issue in my shop. I know it's there and I know how to deal with it. Turn the volume down when idle or keep your hand on the strings. I've also found that if you hold the guitar in a certain angle it goes away. It does not happen in my music room.

I think the interference is coming from a circuit breaker box that is within 10 feet of my shop setup.

Take Tubenit's advice and move the show to another venue and check it out there.

[TIMBO]

Hi guy's, Thanks for all that. I did try to rule out external problems (leads, power outlets,wife etc.) but the ceiling fan i thought might be the problem because when the speed setting was turned a click came through the speakers but that was all.

I work as a civil contractor to the local electricity company and part of what i do is putting copper cable(70mm sq.) in the ground to earth the metal structures. I don't understand all the theory of doing this but sometimes when the earth grid is tested the ground is not conductive enough to dissipate the electricity, so earth spikes are driven into the ground and connected to the cable to help dissipate the electricity.

As discussed the house grounding is via an earth spike at point of entry (meter box) so i'm thinking that the ground around the earth spike may have become dry and non-conductive due to the lack of rain over the past few months  

So hopefully i can find an electrician at work that could shed some light on this.
I looked up my post on the original TOS and i had little problems with BUZZ os i believe that something HAS changed  

Thanks

I asked an electrician today if the ground spike for the house could be the cause and he said that it would be very unlikely as the neutral and earth are bonded at the meter box and that if the earth should be disconnected there are other groundings in the supply network. I am yet to try another location. Thanks

[TIMBO]

I asked an electrician today if the ground spike for the house could be the cause and he said that it would be very unlikely as the neutral and earth are bonded at the meter box and that if the earth should be disconnected there are other groundings in the supply network. I am yet to try another location. Thanks

[PRR]

Indoors, it does NOT matter if your electric is connected to dirt. (What you do at work is for much bigger outdoor systems.)

The amp chassis, guitar cord, guitar shielding, and ideally your body should all be at the "average" of all the electrical fields in the room (wiring, lamps, etc).

Measure resistance from guitar cord all the way back to the screw on the wall-outlet. Should be same as touching probes together, dead-zero (or as low as your meter gets). Certainly less than a few ohms. You already tested from guita cord to IEC and that was OK; if g-cord to wall fails, your IEC cord is bad (or you have busted ground somewhere).

Now measure AC Volts from wall-outlet U-hole to the other two holes. Ignore the one that jumps over 100VAC. The other one should be very-nearly zero. If there are other loads in the house, a volt or two is normal. If you have a long feeder (like mine) and run the microwave or toaster, 2V or 3V is not-wrong. However anything over a Volt ground-to-neutral with no heavy loads is suspicious.

What is the history of the house? Built in 1999 with master electrician and sharp inspection? Or farmer-wired bit-by bit in 1909, 1931, 1959?

EDIT I just noticed your Location says Australia. No major difference except "U-hole" may be round and "over 100V" will be headed for 200+V. And I dunno how much idiot-wiring is tolerated there. Still, and as your sparky says, G and N are tied in the fusebox and should be nearly the same at every 3-pin outlet.

[TIMBO]

Thanks PRR,All measures out as OK and the house is about 5yrs old and has a earth leakage trip safety switch. Its now down to and if you can believe that this could be the case that the body emits electricity that interfears with the guitars electronics this is the next thing to fix (but its not  just one guitar but all three). Just posted RADIOACTIVE MAN. Thanks

[archaos]

You're right Timbo, we do are radioactive men at different levels 
Yet I've well-understood what kind of nightmare you're living...
I just dunno why, but I feel like stg could be wrong with the input jacks. You used isolated jacks didn't you (your pics are a bit blurry for me, sorry I'm as blind as a bat) ?
If so, how & where are they connected to the chassis ? I mean the ground-chassis connection must be done right at the very input of your amp, but I didn't notice that in your .sch files.
Furthermore, how did you make use of Merlin's grounding scheme ?