What's the buzz, tell me what's happening with my Teisco Bass ?

[windmill]

Hello

So I have a 60's Teisco bass with one single coil pickup which makes an electrical buzz when plugged in.

Its a strange thing, I'm mystified

When the volume and tone knobs are turned down it silences the buzz
The buzz can be significantly reduced by turning the guitar about 90 degrees from the amp.

I have shielded the cavities with copper tape, it has an aluminium pickguard.
Touching the metal parts of the guitar makes no difference.

When I touch some of the soldered connection the buzz increases.

Any suggestions as to how to eliminate or lessen the buzz?

Thanks

[oid]

Does touching the metal barrel of the 1/4" plug lessen it? If so run a string ground to the bridge. Many of these sorts of instruments have no string ground and aluminum can produce some very unconductive oxides which can isolate the pickguard from ground, which is one reason aluminum pickguards often have copper shielding stuck to them.

And/or you just have a noisy microphonic pickup, tapping on the pickup comes through the amp loud and clear? If this is the case you can pot it or have it rewound, both will change the sound considerably.

It could also just be something in your environment throwing a good deal of EMI, try unplugging everything about that can be reasonably unplugged and turn off the lights, see what happens. I do not expect this to be the case since turning 90 degrees to the amp is a classic sign of a missing string ground and or a very microphonic pickup.

[windmill]

Thanks for the response

There is a wire which runs from the bridge to the back of the tone pot. Is that ok

The pickup is simply a coil of wire which sits on a couple of magnets and and a piece of metal which fits in the coil with threaded holes for the height adjustable screws. Simple really and a bit difficult to pot as it is !

When the pickup is tapped it can be heard through the amp quite clearly.

It is similiar the one below with the side magnets and the magnets on the base but without the base plate.

The picture is almost the same bass and shows the height adjustable pickup screws.

[dobrojoe]

Microphony and hum are two separate issues. Microphony can be cured by potting the pickup in wax - which is something you can do easily at home.

If you don't have a base-plate, you will get hum. The base plate, apart from providing a foundation for the rest of the bits, acts as a shield and connects with the pickup cover and ground wire. If there is no base-plate, your best bet is to line the pickup cavity with screening foil and connect it to your tone pot casing.

Ideally, ALL grounding should be done to one single point - the casing of you tone pot. If there are other ground points, you can have a 'ground-loop' but it is hard to imagine that this would be a problem with such a simple, single pickup guitar.

[oid]

Microphony, hum, and buzz are three separate issues, exceedingly microphonic pickups do make more noise, never figured out why though. The old Japanese pickups are almost as a rule exceedingly microphonic, but that is a good part of their sound. We will get there eventually, base plates will cut back on some of the hum, but not buzz, buzz is ground not EMI, semantics sort off, technically it is all EMI in the case of pickups.

I would reflow the solder joints in the ground path and check that the pickips case is grounded, if you got a meter check for continuity from the pickups negative to the strings.

[windmill]

Have made some progress with this.

Took it round to bloke who knows his electronics, after surmising that the pickup is the problem, he then attached a capacitor to a volume pot tag and its casing.

This reduced the amount of hum significantly, although it is still there.

Thanks for your help.