Deville 410 noise

[dev]

Hey hope i am on right area for some help from other members.i have noise problem with my blues deville 410..it has a high pitch squeal.when on drive channel..move the drive knob past 3 and hellfire breaks loose,ear piercing high pitch sqeal..on normal channel all is good..just want nice functioning amp again..it is a reissue..built 2004 by all accounts..any help would be great..

[52 Bill]

Hey hope i am on right area for some help from other members.i have noise problem with my blues deville 410..it has a high pitch squeal.when on drive channel..move the drive knob past 3 and hellfire breaks loose,ear piercing high pitch sqeal..on normal channel all is good..just want nice functioning amp again..it is a reissue..built 2004 by all accounts..any help would be great..

Welcome to the place. What you are describing sound like the amp is oscillating when you turn up the gain. This can be caused by a number of different things.

Bad tube or a bad filter cap first come to my mind. What sort of skill set do you have? As a first test, you could try and swap the position of the first two tubes to see if there is any effect.

[nsubulysses]

This should help too -- Squeals

I would think lead dress, or tube as 52 Bill said . Tube is easy to check. Lead dress not so much because you would have to move wires around with the amp on, which is potentially dangerous. Need chop sticks

[Jazz P Bass]

Right behind the input jacks is a large capacitor, labeled 'C36'.
It is a 22uf/ 500Volt cap & it is most probably bad.

[Chuck H]

If the amp is stock (and since it's a PCB design) it's not lead dress. Also, if the preamp filter is faulty I should think it's wise to at least consider the main filters as well which work harder. Filter caps are a common fault in some of these amps and their failure is known to cause oscillation.

I'd try the preamp tube replacement. A microphonic preamp tube is an easy fix. If that doesn't fix it, suspect the filter capacitors next.

[Jazz P Bass]

By measuring the Vac ripple on C36 in normal mode & then in drive mode. the cap can be ruled in or out.
When C36 goes bad, the guitar signal can actually be seen to ride on the + end of the cap.
The cap is there to prevent that.
Hense the name 'decoupling capacitor'.

[TimmyP1955]

If it has JJ power tubes, make sure that the grid stoppers are mounted directly to the tube socket as opposed to mounted on a PCB and connected to the socket with a length of wire.