5e3 amp build help!

[Guitardednow88]

I'm building a 5E3 clone amplifier and have fitted the components into an old boombox enclosure to make it an amp head. As soon as I turned the standby switch on, it starts oscillating and feedbacks. I notice the output tubes have blue spots that appear immediately after powering on the amp as well. I almost feel it has to be a grounding issue. If I touch the enclosures I used to mount the tube sockets I can almost get some noise to go away. I also have a video of me moving the speaker jack around and it going completely away when it's in a certain spot...very weird. I have checked the schematics more times that I would like to admit. Not sure if it's a lead dress issue? Or the fact the the entire enclosure is a plastic boombox? And help is greatly appreciated. Thanks!

[Stuff4bikes]

They are going to want to see pictures of the circuit....
I am fairly new to amp building but I have built a 5E3
How are you grounding the input?

[glass54]

Do you mean it howls at some frequency, no control of frequency?
Could be your layout? could be earthing problems? You need to be very particular with earthing/shielding in a plastic enclosure.
(Maybe even use a compact metal sub-chassis??)
As S4B said, some good resolution pics of your project would help. 

[ALBATROS1234]

My first amp squealed like a banshee, it was because I was thinking like an electrician. I just grounded stuff wherever.  You need a good grounding scheme , try a star ground,  that's my usual method.

[Guitardednow88]

I'm trying to post pictures but it's saying to the files are too large?? It's just a Standard picture from my phone. Anyone know how I can post pictures?

[sluckey]

Take smaller pics with your phone.

[Guitardednow88]

I used new bare pedal enclosures to mount tube sockets. Left side has rectifier and output tubes and right side has preamp tubes. Power transformer in left of center. Grounding is probably not the greatest. I have all earth grounds going to the isolated lug where the old radio antenna is. Should I move them all to a bolt on the power transformer?

[Guitardednow88]

Pic

[Guitardednow88]

I'm trying to post this pic after resizing.

[sluckey]

These kind of projects are doable but usually require much greater skill than just building in a traditional chassis.

[Stuff4bikes]

It's hard to tell if your wiring is correct when the pictures don't show anything landed.
You need to keep filter grounds seperate from preamp grounds....
Some people include the preamp filter cap with the preamp ground.
I ground my boards,  pots, inputs, filters exactly like the circuit I am copying if possible.
Also I find turret boards more eye appealing if the legs of components are bent
And soldered in the hole in the turret.....connecting legs with wire is easier when its
Soldered to the base of the turrets.

[timmyjoe]

I'm very new to this, so this is probably a wrong direction in terms of a fix.

Did you do a simple 5E3 circuit, or did you add in the popular negative feedback option? Negative feedback can be wired wrong and create a positive feedback. https://robrobinette.com/5e3_Modifications.htm#Switched_Negative_Feedback

[uki]

Although the enclosure idea is really nice, remember the fact that tube amps usually run really hot   
that plastic enclosure may suffer with the heat, maybe deform/melt.

About the circuit problems, post the schematic you are following, check twice all connections and component values.
post pictures of the circuit with the working amp, so people can gather info and help you!

[HotBluePlates]

I used new bare pedal enclosures to mount tube sockets. Left side has rectifier and output tubes and right side has preamp tubes. Power transformer in left of center. ...

But you haven't mention the Output transformer, right next to the preamp tubes.

Photo doesn't show the turret board in place, but I'm guessing that went across the open space in the middle?  If YES, then you have very large signals from the output of the amp right next to tiny, high-impedance signals at the beginning of the amp circuit.  And that's what is probably causing your oscillation.

"But everything is roughly where it would be in a normal amp build."
That's true, except you don't have the benefit of the metal chassis acting as a shield between the output transformer & the preamp circuit board.

[Guitardednow88]

Sorry everyone. I'm pretty new to this forum platform and am learning how to navigate replying and posting pics and such. It's really hard to see but the board is mounted upside down right above the power transformer.

[sluckey]

I've looked at you last pic and I think I have an idea about your problem. I think a lot of your grounds do not have a connection back to the PT red/yellow wire. Use your ohm meter to check this. DON'T USE THE IDIOT CONTINUITY BEEPER! Connect one probe to the red/yel wire. Now move the other probe to every one of your ground points, noting the actual resistance. Every ground point must show zero ohms resistance to that red/yel wire. I bet they don't.

I have no idea what layout you may have used or what your electronics background is. Use the linked 5E3 layout as a guide. Notice all those ground symbols? Every one of those will have zero ohms resistance to the red/yel wire. Many of these are provided by the metal chassis. But since you built your amp on a non conductive platform, you must use a wire to string all those ground points together.

     https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_5e3.pdf