I just bought my first real practice amp -- a 25 watt Washburn. I plugged in my latest build (which has 2 humbuckers and a Tele control plate) and it sounds great, but when I flick the amp's overdrive switch, it gets noisy (ha ha) with the usual grounding-problem hum. When I touch a finger to the metal jack plate, the hum drops off.


Am I supposed to run another ground wire to the jack plate, or is there something wrong with my Washburn amp?

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Hiya, You will need a wire from any part of the ground circuit, usually one is run from the back of the volume pot, up to under the bridge, it only has to be touching the bridge, no soldering is required on this end. This will ground your strings and will have the same effect as touching the jack plate.

 

Hi Jeremy:

 

I have already grounded the bridge, which grounded the strings and the trapeze tailpiece I used. The only things making noise are the jack plate and, to a lesser extent, the adjustable screws on the pickups.

Errm, is the output jack wired the right way round, that can cause hum too, caught me out once, just a thought. jez

Mister Scott (the Nacho Libre face wrestling mask on your profile pic still cracks me up, because I imagine James Doohan saying, "Captain, I canna hold 'err enny longurrrr!"),

 

Anyhoo, if you've wired your ground from the pot to the proper lug on the jack itself (which should be the one that connects to the inside ring of the jack, not the lug that is part of the outside ring that has the long tip), then the jack plate should also be grounded, since it holds the jack itself in place. All of your grounds from bridge, pickups, etc. should terminate on the back of the pot, according to most of the wiring diagrams I've seen, and then a single ground wire runs to the ground lug on the jack. Can you post a photo, sketch or diagram of your wiring set-up?

Also, it could be that the ground on the back of your pot may just be loose, or improperly soldered. Many people seem to be having trouble lately with proper soldering of the ground to the back of the pot (me included), usually not scraping enough down to bare metal on the back of the pot. I'm seeing lots of posts here lately about having to resolder ground wires. Another issue could be a loose connection in your guitar cable; some of mine go wonky when I least expect it, because they get pulled on so much. Then, see if your amp has a 3-pin plug (it probably does, but it never hurts to ask) as opposed to a two-pin; that third pin is your ground into the wall socket. Sometimes, the smaller practice amps are incorrectly grounded and or shielded internally, as well, even when they bear the UL listing seal of approval. 

 

Electricity is a beeyotch, ain't it? Trying to give advice without seeing the setup, much less being able to trace the current with a multimeter, puts one in the same position as the tech support guy with the script on the computer help desk phone bank: "Is your machine plugged in? Have your turned on the power switch? Have you..."

S-O-N-T,

Thanks for your message. THere's a lot of helpful info there. Here is an update of this situation:

Before you sent your message, I resoldered a number of the lugs and grounds in the build. i replugged it in to the practice amp, and the problems were still there.

I tried out 2 other CBG builds of mine that were sitting near, and both of them had the same issues as that latest build: ground hum when I touch the pickup screws or jackplate while plugged into he practice amp.

Now here's the kicker: I dug out my 2-watt, battery powered Danelectro mini-amp. NONE of the grounding issues were there. This leads me to believe I bought a faulty used amp, and I'm not sure how to fix it.

MS,

It was a used amp? If you can get me a model or serial number, I can research it on the amp forums, and see if it has any known grounding issues. Another thing you might try is to take your git over to Guitar Center, plug it into several of their demo amps, and see if you still have the problem. We can sort this out; could try taking the issue over to the CBG wiring Group and see what they say. They'll probably want to see your wiring setup, with both diagrams and photos.

S-O-N-T,

It was an amp i purchased at a Pawnshop. It's a Washburn Bad Dog BD25R. It has 2 channels, and on the first channel, the hum isn't so bad. It's when I select channel 2, which has the Overdrive feature, that hum becomes really noticeable.

Scotty,

Ok, I'll do some digging, see what I find, and get back to you. May be a few days, but I will get back to you.

Scotty,

 

Here's what I got so far: one reviewer at FixYa.com, in a post on a related Washburn amp, say the capacitors on the power block are used to cancel the 60-Hz hum that comes from your house current. It is possible that one of these is bad, or maybe one in the Overdrive channel on your amp. Another reviewer in the UK suggested making sure that the outlet you are plugging into is actually properly grounded (I have had grounding problems with two houses I've lived in in the past 10 years, with both being improperly grounded, and outlets varying in their ability to cancel that 60-cycle noise). Apparently, a fair number of amps, including some famous names and models, not just yours, have insufficiently grounded power sections. Will keep looking, not much info out there, haven't even found a wiring schematic for your Bad puppy yet.

Hey, i found the schematic... Washburn sent it to me.
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