Still humming some.

[Revor]

So my new 5E3 is still humming a bit.

I had it apart last night and did some little heater wiring mods that helped a bit.

I have been reading about grounding the centertap (a real one, green w/ yellow) to the cathode pin of the Power tube. Pin 8 righ? Going through the 250 Ohm Resistor and the 25uf Cap to ground?

[Chuck H]

That would be something to do once you have the amp working correctly. Once the hum level is normal you could then look into ways of reducing it further. If your hum level is abnormal something is wrong and needs fixing. The DC elevation trick is an improved circuit for a properly working amp. Not a circuit for correcting problems but for maximizing potential.

Look at it like this. If your rain gutters are too small and tend to overflow before the water reaches the drain, adding a better drain won't help much. You should put up higher capacity gutters first.

[Revor]

Gotcha, I do believe that is working correctly.
The amp sounds great! The hum goes up and down with volume with an instrument attached or not, a bit noisy with a Strat, quiet with My LP as I would expect. The hum abrupty goes off within a half second of switching the standby switch.
My wiring mistake was running the heater wires from PT directly to the filiments originally and adding the Pilot seperatly, oops. As a test I simply disconnected the pilot lamp it did reduce some of the hum so I will need to rewire that correctly.
Input side grounds are on their own seperate buss and ground at the #1 input jack. The Cathode grounds at teh PT stud along with the CT's and the line ground.
I tried two other things on helped one did not. The OT ground for was originally soldered to it's case which grounds to the chassis, I lifted that from teh case and soldered a connection to the ground side of the output jack, that made some difference. I also noticed the the output side of the OT was facing the PT, so I turned it around, no difference.
The filiment wires are run Marshall style.
The wires connected to V1 are very Microphonic, (normal?)
Tubes have all been swapped with exception of the rectifier.

[Chuck H]

Gotcha, I do believe that is working correctly.
The amp sounds great! The hum goes up and down with volume with an instrument attached or not, a bit noisy with a Strat, quiet with My LP as I would expect. The hum abrupty goes off within a half second of switching the standby switch.

If it's quiet with humbuckers then your hum source is external to the amp.

My wiring mistake was running the heater wires from PT directly to the filiments originally and adding the Pilot seperatly, oops. As a test I simply disconnected the pilot lamp it did reduce some of the hum so I will need to rewire that correctly.

Right. You definitely want the filament wiring to take the shortest reasonable path. There should be no problem having the filaments wired and then the pilot parallel from the same starting point. It's the same amount of lead length as going to the pilot first and then to the filaments.

Input side grounds are on their own seperate buss and ground at the #1 input jack. The Cathode grounds at teh PT stud along with the CT's and the line ground.
I tried two other things on helped one did not. The OT ground for was originally soldered to it's case which grounds to the chassis, I lifted that from teh case and soldered a connection to the ground side of the output jack, that made some difference. I also noticed the the output side of the OT was facing the PT, so I turned it around, no difference.

It's always hard for me to get a picture from a description. But I can say that grounding scheme can make a big difference. One thing to consider is that it only takes a very small amount of coupling for hum to present and even wire has resistance. This is why daisy chained ground leads can be a problem. Especially if you have high current circuits grounded with sensitive preamp circuits.

The filiment wires are run Marshall style.

You mean a twisted pair instead of the stock wiring? That's pretty normal on 5e3 type designs anymore. It is important to make sure you have the right side of the 6.3V secondary going to the right tube pins to achieve hum cancellation.

The wires connected to V1 are very Microphonic, (normal?)

Yup. Normal. It's also pretty standard practice on these amps to include a shielded input lead.

[Revor]

If it's quiet with humbuckers then your hum source is external to the amp.

Sorry I wasn't clear, when I plug in an instrument the Single coils make some noise like I would expect, teh HB's are quiet. This is an observation apart from the hum.

As for Marshall type heater wire routing, twisted pairs stuffed down along the edge of the chassis as compared to up in the air like many I've seen.

The "buss" was a suggestion that might reduce hum.

I chicken scratched the grounding I used in red.

[Revor]

"If it's quiet with humbuckers then your hum source is external to the amp."

Sorry I wasn't clear, when I plug in an instrument the Single coils make some noise like I would expect, the HB's are quiet. This is an observation apart from the hum. The hum is present without instruments.

As for Marshall type heater wire routing, twisted pairs stuffed down along the edge of the chassis as compared to up in the air like many I've seen.

The "buss" was a suggestion that might reduce hum.

I chicken scratched the grounding I used in red. the cases of the pots are not grounded, they ground directly to the buss with exception of the tone pot that grounds through the cap. All of the input and output jacks are isolated from the chassis with Fiber washers with exceptioon of #1 normal, it is the ground for that end of the chassis.

[loudthud]

Hum can enter the signal chain from two different paths. 60Hz hum (sounds like a low organ note) comes from heater wiring usually. 120Hz hum (sounds like a buzz) comes from grounds in the power supply. If you flip the Standby switch off, the 120Hz hum should stop instantly, the 60Hz hum will fade out for a second or two.

Your grounding looks fairly good. The two things I would change are: 1) Move the ground from the filter cap and 6V6 cathode resistor to the same transformer bolt as the center taps. 2) Remove the connection for the speaker jack ground and just ground the jacks to the chassis. The ground from the output transformer should go to the same place.

Moving the heater winding center tap (Green/yellow) wire to pin 8 of the 6V6s will get rid of some of the 60Hz hum.

[Revor]

Thanks Loudthud!

I will try that tonight and we'll see how it goes.
Last night I had enough time to warm it up and measure the level of the hum so I would have a baseline to work against.
When first powered up and the hum appears it sits at about 40 db with the meter about a foot from the speaker, after a good ten minutes the noise level is at about 52 db and there it stays so it's probably as warm as it's going to get just sitting there.
I also got out mu chopstick and moved some wires around to see if it made a difference, it did in some cases but I found alarmingly that the input wire from the #1 input jack to pin two on V1 was very sensitive, making a fair bit of noise if I probed it. I also found that if I push on the two PT studs closest to the outside of the chassis I got a lot of crackle and static !?!?! Got to look into that.
After I put it back together I took an hour to just play the guitar, I love how this amp sounds!

[Bruce / Mission Amps]

Simple.
If it hums with out anything plugged into the input jacks and it gets worse with the volumes up... then one or more of your input jacks are not working right.
The switching portion of the jacks are wired wrong, not shorting to ground or misaligned.

[Revor]

Hi Bruce and thanks!
I will look again, while poking around with the chopstick last night, one at a time I would push the the tip portion of the jack away from the grounding portion expecting to hear a difference. But I never heard one, if I understand correctly I should have heard the hum grow louder as one of the tip connectors was pushed away from the ground connection.

[Revor]

Hookay I made sure my grounds at the input jacks there was a problem so I fixed it. Now when I push a tip away I get noise!
There's still a hum though dead quiet now at zero growing loud with the volume. I spect I'll check for more gounding issues.

[überfuzz]

Congrats! Are you sure the hum is more than, lets call it, a vintage hum?

Seriously, compare with an amp or two. Is the hum in the same realm or worse..?

[Revor]

That's a very good point! When I hear "whisper quiet" and "Dead silent" when folks refer to their amps my mind goes into "get the hum out" mode! Old amps do hum a bit.
To be honest I have a Bassman Blackface that I just recapped and put new tubes in. I should fire it up and measure it for a comparison. I know it had hum I just never got that excited about it other than after I recapped it and it did quiet down a bit.
Maximum hum on the Deluxe is 53 db at a foot using the high tech (read free) sound meter app on my Atrix.

[Jazz P Bass]

The hum really must be defined.
I think what must be a measurement is the amp on & no input connected.
All controls off.
Measure the residual hum at the speaker connection (Vac)
That is the amplifiers hum.
If any controls affect that hum, that may or may not be an issue.
Now when you plug in a guitar & start turning controls, that is a different tiger stripe.

[Revor]

A great place to start.
I think this hum can be narrowed to a 60hz hum, it is simply a hum, no crackle, fizz. Like a mantra, a deep mmmmmmmm.
All measurments have and will be done w/o an instrument or cable plugged in. No extra antenna's for RF to get in.
With all controls to zero the hum is well nearly non existant.
With using volume controls (either) the hum increases relative to the level of volume, to a point. I can define this further at several settings.
As the volume is increased to above ten the hum is "over-ridden" by break-up that I will describe as fizz, like blowing out with your upper teeth placed upon your lower lip as you would at end of saying "F". This is a secondary issue which I would sorta expect.
The amp is buss grounded as shown in the layout before. I have since grounded all the input jacks better, grounded the CT for the heater to DC (made a difference) Poked and prodded, removed the twisted pair to the pilot lamp, re-flowed each connection (I'm good with an iron)
I'll report back.