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right, my guitar squeals, i put my finger on the metal plate with the volume knobs on and it stops the squealing (mostly). i therefore deduced that my guitar is picking up oscilations, and i need to put a decoupling capacitor across the source (pickups) am i right or am i drastically wrong?
if so, around what size capacitor shall i experiment with?

[Alex]

I had a similar problem with my guitar, and had to rewire it because the live wire exposed and soldered really badly. I'd check the wiring. Decoupling capacitors are only typically used in DC circuits I think. Z=1/jwC and all that malarkey.

[soundian]

Yup, sounds like bad wiring. That's certainly the first avenue to explore. Cheapest to fix and the likeliest. Bad earths are a very common problem.You seem to be earthing it when you touch the metal plate, which is probably in electrical contact with your volume and tone pots. Does it do the same when you touch the stings as well?

well, bad earthing was my first theory, i checked the wiring and there was some bad connections, re-soldered them, thing is, i cant see any connections to the metal plate witht he pots on, which is why i changed my theory to picking up wobulations (it happened on a regular basis in the labs last eyar when i did electronics, but we had a scope, a little easier to fualt find with an oscilly)) and its cured by using a decoupling capacitor, i cant see why adding in the impedance of the capacitor would make any difference, am i wrong? im going to maplin to buy some tubes and a set of capacitors, ill experiment after iv resolered all the wiring.
i think the strings do effect it aswell, and the plate that the strings are attached to aswell, but strings to lesser extent.

iv got another possible solution - , nothing guitar related turns out,


"(Note... the high pitched ringing sound your amp usually makes is not parasitic oscillation. It is a microphonic preamp tube, a problem that is far more common. Here's how to tell the difference: pull the guitar cord out of the input jack. Turn it up really loud and smack it. Does it make the amp ring more or stop rInging? Yes? Then reach around back and tap on each preamp tube individually. The one that makes the sound needs to be replaced.) "

[David]

if its a cheap guitar it couls be a microphonic pickup, that would need replacing or wax potting to stop

David

it is,,,
i ordered new pots and switch selector, gonna re-wire the whole thing with new parts and see what happens, otherwise itll be new pickups, i havean open coil and a closed coil, squire tele, which one dya reckon is the offender?

[soundian]

Originally posted by lime
it is,,,
i ordered new pots and switch selector, gonna re-wire the whole thing with new parts and see what happens, otherwise itll be new pickups, i havean open coil and a closed coil, squire tele, which one dya reckon is the offender?

How did you come to that conclusion.

And surely if you change pickups, the squealing will stop if it's ONE microphonic pickup. I'm not ruling out both, or there being more than one problem.

i didnt really come to any conclusion, i just got fed up and decided to gut the bastard.

[Alex]

I'd just ground it properly.