drilling brass plate for fender-like deluxe build rework

[mikepukmel]

Hi All,
Finally scrounged up a small drill press. Id like to rework the brass plate that I botched on a Deluxe Reverb build. Having some difficulty figuring out how to drill the pot holes in the right spot. I think if I drill it first, then have someone with a brake bend the plate, the holes probably won't line up. And if I get the plate bent first, and mark the holes with a sharp scribe, it will be a real challenge to clamp down into the drill press due to that odd angle. Any suggestions greatly appreciated.
Thanks
MP

[Helmholtz]

I personally don't think it's worth the trouble.
A ground bus wire soldered to pot cases a la Marshall will work the same.

[mikepukmel]

Thanks Helmholtz. That's what I have working (mostly) now, wasn't sure if it was 'the best way to go". I have a bus wire, its not soldered to the back of the pots, bit is connected to the turrets. Should I leave the plate installed and ground it separetely, e.g. wire from the plate, soldered to the chassis someplace?

[Helmholtz]

With the bus wire connected to pot cases, a plate is not necessary.
Ground wires connecting to the plate should be soldered to the bus wire instead.

[Chuck H]

And I'll add...

If your bus wire is currently "connected to the turrets" the I have to assume these are two grounded turrets on the board? You should only be grounded on one end to avoid ground loops, noise or potential instability. Preferably the input end of the board and only use the bus for the preamp circuits.

[Enzo]

The brass plate was there in the first place to be easier to solder to than the chassis. If you use something else to solder to, like a buss wire, then the brass plate serves no purpose.

[nevetslab]

I gather you don't have a Whitney XX Punch set. I never had the funds for a bench-mounted long-lever punch with their more-expensive punch & dies, but the XX punch I have has a deep throat, (and I have punch/dies from 1/16" thru 1/2") allowing me to punch all those thin brass plates that begin in the flat pattern,

Years ago, I invested in layout tools (calipers, small adjustable machinists squares & combination squares with blades out to 24". So after careful measuring of the hole locations onto a drawing, I'd then do the layout with a scribe and measurement tools to mark up the brass plate with scribe lines for punching the holes and bending. Granted, I haven't tackled a full width brass grounding plate as used in the earlier Fender chassis, but I long ago stopped trying to drill thru thin stock and find the resultant holes where I had intended them to have wandered a bit from their C/L, Without a small brake for bending, I'd clamp it on a flat surface, and slowly start knocking the flap into the direction of the fold Maybe even go as far as cutting the angle on the edge of the wood surface being used for the bending form so you can knock it into being flush with that 'wooden bend fixture'.

[Chuck H]

...

https://www.tedweber.com/5e3bp/

[mikepukmel]

This was patient zero, first amp build I ever did, so you can imagine what it looks like inside (despite my best efforts). I managed to drill the plate, can't believe its been this long, used that, removed it, put bus wires in, because I thought it was causing noise problems. Noise is still there. This was, without a doubt, the most fun project, thanks in large part due to you all, all your great suggestions and comments. Thinking about taking this amp back apart, and going through one last re-wiring, and try harder this time to make it as close to the original circuit as possible. its got a few odd things in there. And my first attempt at heater wiring is not, how should I say, photo worthy.

[Chuck H]

And my first attempt at heater wiring is not, how should I say, photo worthy.

Neither was mine. And maybe not even my most recent build

[mikepukmel]

I think something like this.

[Helmholtz]

Don't overlook that a Fender amp has quite a few not so obvious chassis grounding points including all input and output jacks as well as the reverb connectors.
At all these points ground return currents can flow into and through the chassis, making the chassis part of the circuit ground.
So when you deviate from the original ground wiring, results are hardly predictable.

To me the original grounding of my vintage Fenders works well enough.

[mikepukmel]

Don't overlook that a Fender amp has quite a few not so obvious chassis grounding points including all input and output jacks as well as the reverb connectors.
At all these points ground return currents are flowing into and through the chassis.
So when you deviate from the original ground wiring, results are hardly predictable.

To me the original grounding of my vintage Fenders works well enough.

Thanks, Helmholtz. Yes, that's where "I am" now. Ive re-read Merlin's chapter on grounding, looked at what I did in my franken-deluxe build, then re-read the layouts, looked at more photos of the original amps. I have a brass plate that I had originally made, badly. Its too thick so that the shorter threaded section of the pots don't have quite enough thread for the nut to hold the pots in, with the thick plate in there.

The grounding "scheme" I have now, is, I think, causing ground loop/hum issues. As you write above, I counted something like 16 or so ground points, tied in to the chassis directly. Im sure I don't understand the brass plate thing. The plate is not soldered to the chassis, it has, in the factory 64 amps, several wires running from the turret board. So, that plate could have "good" grounds to the actual chassis in multiple places? As the years go by and the brass and steel oxidize.

[Helmholtz]

In the other tread we already told you that the brass plate can be replaced by a bus wire (I'd use maybe 1.5mm dia) running along the backs of the pots.
Run the ground wires from board to bus along the chassis to minimize magnetic loop area.
Are you really sure you have a ground problem? What's the frequency of the hum? Scope pics?

Pease don't jump between different threads.

[mikepukmel]

In the other tread we already told you that the brass plate can be replaced by a bus wire (I'd use maybe 1.5mm dia) running along the backs of the pots.
Run the ground wires from board to bus along the chassis to minimize magnetic loop area.
Are you really sure you have a ground problem? What's the frequency of the hum? Scope pics?

Pease don't jump between different threads.

Thanks, Helmholtz, just went back and forth, got all the info you guys posted now.
And, sorry about bouncing threads, its annoying. I'll stop doing that.

***

After reading through a bunch of threads again, I think there is a ground loop at least. maybe other issues. What I did had two problems: I did not do the ground bus wire correctly. So, the input jack must have a ground there due to the Fender wiring. I ran a bunch of wires to the chassis, under the turret board right below where first input jack is. And there is the "dirty" ground lug near the power transformer, with: 1) the negative side of the reservoir caps, and 2) center tap for the transformer. But the ground for the 2 reference resistors is grounded at another point. And also you mentioned the reverb ckt. So I think there are at least 5 places that circuit reference is tied to the chassis.

I will start to take it apart and write down all MEF suggestions and make a plan. (and not drive everyone crazy with thread switching )

There is a lull at my work (praise the lord) so I have some time nights and weekends to get this amp cleaned up. Mike K posted some photos on the other thread, wow, wish I could get to that level of wiring lead dress.


General question, sorry if its a dupe: It looks to me, untrained eye, that Fender, when they worked out the original amps, they minimized the length of every wire put into the amp. The wires from the ckt board to teh brass plate, very short. The wires from the ckt board to the tube sockets, same. And they didn't use any wire on the pots, they just soldered to the back of the pots.

For the preamp end, could long, rambling ground wires pick up signals? maybe in addition to ground loops, some of these wires are picking up junk that if the wire was shorter, or not there at all, would be ok?

(Thanks to everyone for putting up with me! )