Oscillations problem help

[Helmholtz]

Then a grid leak resistor will be necessary, but is not my case, I omitted the grid leak from circuit just for this reason. Is not necessary for my aplication so I didn't putting in.

I don't understand that reasoning. Even an active bass might have an unterminated output coupling cap - though it's not good practice.
What's wrong with adding the resistor - even if it's typically not required?

[catalin gramada]

Egal with or without, I may put in as a "good practice". Still don't see the ground loop in my layout please.

[vintagekiki]

Ground loop can't even see, because your layout is not complete, because it doesn't show the actual layout of the complete assembly.
Layout means a photo or detailed drawing of the wiring and layout of all components on the chassis.

1)
Here’s idea for the wiring and layout, how Fender does it.

champ_5f1_schem.pdf

champ_5f1_layout.pdf

[catalin gramada]

Hey VK , I revired whole circuit as you drawing. Grounding and changing shielded wires with normal wires and put it back in circuit one by one...nothing works to cure osscilation. It is identical same manifestation as it was before. So I rewired everything back and decided to close the problem with a grid stopper but not as big as 100k tried before...And surprise even a 470 ohm in grid soldered directly at the socket stopped the oscillations. I changed with 1k just to be sure and leaved in place.

[vintagekiki]

Check the hot pins on the input jack whether make good contact with the gnd pins.
It happens that everything looks fine and the switching contact is unreliable.

[Helmholtz]

Hey VK , I revired whole circuit as you drawing. Grounding and changing shielded wires with normal wires and put it back in circuit one by one...nothing works to cure osscilation. It is identical same manifestation as it was before. So I rewired everything back and decided to close the problem with a grid stopper but not as big as 100k tried before...And surprise even a 470 ohm in grid soldered directly at the socket stopped the oscillations. I changed with 1k just to be sure and leaved in place.

I'm not surprized that even a small grid stopper helps.

And I don't think VK recommended to repace the shielded wires with normal wires (see post #46).

[catalin gramada]

I'm not surprized that even a small grid stopper helps.

And I don't think VK recommended to repace the shielded wires with normal wires (see post #46).

No he didn't but I did to keep it simple, anyhow the noise was horrible without a chassis bottom shield but same osscilation in same po potentiometer position. I wired shielded then but didn't do any difference for osscilation just reduced the noise. Definitely the grid stopper iwas compulsory. The shielded wire just makes it as quiet as a mouse but no diference mounted in one way or other.

[catalin gramada]

Check the hot pins on the input jack whether make good contact with the gnd pins.
It happens that everything looks fine and the switching contact is unreliable.

Thanks, I know what you mean, pretty familiar syndrome, special with cheap jacks, but not only. Found often the chrome layer act as a kind of isolator and in some circumstances peel off was happen to me for some connectors, dmm probes and also bought from Germany some Chinese turrets with same issues. I don't know if was galvanic treated or just sprayed with some...seems more decorative than electrotechnic layer.

[tedmich]

I cant resist! 1968!

[catalin gramada]

I cant resist! 1968!

They knew what they do it

[vintagekiki]

About grid stopper

#3
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Grid Stopper Resistor Calculator