Loud buzz plugging in effects, main input.

[sonofmickel]

This is probably my newbie-ist question ever. It is in regards to amp buzz.

This is on a single input Fender AB763 circuit, no reverb. Amplified sound is good.
Signal path: Guitar > dist pedal > amp, or even Guitar > amp.
When I unplug a cable the amp makes a non-denominational God awful buzz! It is loud and sounds like the amp will explode! It is not the regular grounding out the cable buzz you would expect.

Another thing: When testing plate voltages on preamp pin 6 V1b. There is a very loud pop when the probe touches. Testing voltage at Pin 1 V1a results in the normal low level scratch when touching the probe.

Related?

[Littlewyan]

Hmm my Express makes a lot of noise if I measure the plate voltage of the 12AX7s, not sure if it makes a loud pop or not. Can we have some gut photos please?

[Smokebreak]

When you unplug the cable from the amp? Or when you unplug the cable from your guitar?

[sonofmickel]

From guitar side. BUZZ!

[Littlewyan]

Thats pretty normal then to be honest. Some amps will squeal if you do that.

[sonofmickel]

To me this is near thermo-nuclear buzz. Almost as loud as reversed OT leads.

[Structo]

Pretty normal and some areas are worse than others.
Especially on high gain amps.

That's why I like to use Neutrik Silent plugs on the guitar end.
If you unplug it, it shorts to ground to silence the input.

Or if you use a tuner in your chain, you can use that to mute the amp when you unplug from the guitar end.

[Reeltarded]

Don't ever do that.. unplug from the amp first..

You have an ungrounded antenna wagging it around. This is like asking why you get holes in your head from shooting yourself in the face.

[pdf64]

This is on a single input Fender AB763 circuit, no reverb

It may seem obvious to you what is meant by this, but readers are going to have to make assumptions about the schematic, mistakes will be made etc.
It's not hard to mod existing schematics in Paint and every Windows PC has got it.