Please help me with my Deluxe Reverb Kit

[vpierceiii]

Hi all. This is my first post, but I've lurked for some time.
My name is Victor and I'm a retired electrician that decided to build a Blackface Fender Deluxe Reverb from the Mojotone small parts kit.
The rest I built myself: chassis, cabinet, etc.
My problem is that I've got a low hum that's too loud (with all knobs turned to one, no guitar hooked up). I've double, triple checked my connections, and all components are brand new.
One thing I did notice though was when I touched my multimeter probe to the plate (pin 1) of the first power tube (V7), the hum totally went away; and came back when I lifted the probe off.
Any ideas?
Here are the specs:
Mojotone AB763 small parts kit,
Mojotine power transformer, choke and reverb transformer,
Tung Sol GZ34/5AR4 rectifier
Tung Sol 6V6GT power tubes (12 watts)
V1,V2,V4, and V5 are Electro Harmonix 7025
V3 and V6 are Electro Harmonix 12AT7
None of the tube seem microphonic or make noise when touched/wiggled.
Filter caps and bias cap have been substituted with F&T
I added the brass plate at the front and tried to follow the ground scheme I see on youtube (Psionic, d-lab, and uncle doug).
Bias is currently set at 16 mA per tube (7.2W / 458V = 15.7mA)
I hope this is enough info for you.
Here are some pictures:

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[vpierceiii]

Here is a picture of it put together:

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[sluckey]

One thing I did notice though was when I touched my multimeter probe to the plate (pin 1) of the first power tube (V7), the hum totally went away; and came back when I lifted the probe off.

Nice work!

Pin 1 is not the plate. Pin 1 is not connected to anything inside the tube. Pin 1 is simply used as a tie point for the 1.5K grid stopper resistor that connects to pin 5 (grid).

[vpierceiii]

Sorry you’re right. It’s not the plate. However when I put my probe on that pin, the hum stopped.

[vpierceiii]

When I touch the red wire.

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[Stevem]

That yellow ground wire coming off of the negative end of the the first two 16uf filter caps needs to go all the way back to where both of the red/ yellow stripped wires from the power transformer are picking up there ground, not to that long brass strip .

I would drill a hole for a long #8 machine screw that you bolt down where all those wires going to ground are now by the Transformer.
Then solder on bare wires rings to all of those wires and stack then on the stud and use a lock nut or a nut with a lock washer to keep things nice and tight.

I say this because it looks like you do not have a big and hot enough soldering iron to make a good ground connection of all of those wires to the chassis.

Daisy chaining grounds in amps / audio circuuts makes for 120 hz noise floor issues like your having. It’s not like wiring up AC power in a house because you’re dealing with a DC voltage ground path.
In a house chaining all the grounds is never a issue.