Fender Twin Amp 6G8

[uki]

Hey guys

I got into the next step on this amp, the amp worked well in the 1st power up (I had someone skilled helping me with it). I've managed to build almost everything right except for some not recommended grounding(I should had read some more about it), there is hum and it is very present, the normal channel works well but in the vibrato channel there is some whistle or high pitch frequency noise. When volume is turned down to zero there is still a little guitar signal going out the speaker(probably due to bad grounding also there is some messy wiring). Oh and when the standby is turned off, there is a loud pop. How to proced now to trace down the sources of the problems?

Related links to this amp:
http://el34world.com/Forum/index.php?topic=18650.msg190792#msg190792
http://el34world.com/Forum/index.php?topic=18968.msg194798#msg194798
http://el34world.com/Forum/index.php?topic=19225.msg198141#msg198141

Here some pics:

[g-man]

Deleted

[eleventeen]

Good eye!

[Paul1453]

It's a Beast!  What you got, 4 6L6's in there?  100W output?  Extremely loud I bet.   

[uki]

In the third photo it looks like the ground connected to the transformer bolt is not tightened down. Can you check that?

Yes, that was loose while doing the sodering, aluminum chassis is too cold and acts as heat sink while sodering the ground wires making it dificult, once sodering was done it was bolted down to the chassis. I know there is some bad grounding there that will be changed, didn't had time yet to modify that.

Good eye!

Indeed !

It's a Beast!  What you got, 4 6L6's in there?  100W output?  Extremely loud I bet.   

Yeah 4 6L6GC 100W !! It is LOUD !!

[Ed_Chambley]

The brown twin is loud, but normally they have a early breakup so it makes them easier on the ears to get a good tone at a lower volume.  I remember getting backstage during Ted Nugents heyday and he was playing a stack of them.

This is a nice looking build.

[uki]

The brown twin is loud, but normally they have a early breakup so it makes them easier on the ears to get a good tone at a lower volume.  I remember getting backstage during Ted Nugents heyday and he was playing a stack of them.

You mean those? https://courses.physics.illinois.edu/phys406/Amps/Amp_Pix/5G8_Twin_Amp/5G8_Twin_Amp_Stack4.JPG
Would the Brown be model 5G8 ?

This is a nice looking build.

Thanks !  This is the "Blonde Twin" 6G8.

This is my 1st built, I did learn a lot in the process, there is lots more to learn I know and things to get right in this amp, it is working surprisingly well without major problems for a 1st, still there is the hum to fix and the whistle in the second channel, didn't get the chance/time yet to work on it. The chassis still out of the cabinet, only going in when the amp is 100% ready.

Here some more pics:

[Ed_Chambley]

The brown twin is loud, but normally they have a early breakup so it makes them easier on the ears to get a good tone at a lower volume.  I remember getting backstage during Ted Nugents heyday and he was playing a stack of them.

You mean those? https://courses.physics.illinois.edu/phys406/Amps/Amp_Pix/5G8_Twin_Amp/5G8_Twin_Amp_Stack4.JPG
Would the Brown be model 5G8 ?

This is a nice looking build.

Thanks !  This is the "Blonde Twin" 6G8.

This is my 1st built, I did learn a lot in the process, there is lots more to learn I know and things to get right in this amp, it is working surprisingly well without major problems for a 1st, still there is the hum to fix and the whistle in the second channel, didn't get the chance/time yet to work on it. The chassis still out of the cabinet, only going in when the amp is 100% ready.

Here some more pics:

No, when I say Brown, I mean Brownface and not the Tolex Color.  His was the Blond Rough Tolex, the same thing I use on most of my cabinets.  I really like the Blond/Oxblood look.

[uki]

No, when I say Brown, I mean Brownface and not the Tolex Color.  His was the Blond Rough Tolex, the same thing I use on most of my cabinets.  I really like the Blond/Oxblood look.

I didn't know that, those details are a way to identify the amps ? And would the 1st half of 60's the golden age of Fender amps? Those Twins are just awesome !
Got some more pics:

[uki]

    

Can the hum be fixed, or did I messed up too much with the layout?  I did read somewhere to not mess with the layout.
What about the whistle or hight pitch frequency when volume is turned up in the second channel, what can that be ?
I would like to hear sincere views from the gurus about the layout and everything else, what did I do that I shouldn't and what can be done to get this to work right if that is the case.

Thank you so much for your time and patience, I really appreciate that !

Here pics with full view of the amp:

[Paul1453]

I'm not a guru or anything, but I did notice one thing I suspect could be a problem.  You have 3 signal wires going above what I believe is your just rectified unfiltered source HV, and then under the yellow and green twisted wires that may also have some AC hum on them.  I would try replacing those with shielded wires, I would suggest using shielded wires wherever your signal leaves the board, and not running them between or close to other unfiltered HV or AC heater wires.     Those three wires might also explain the pop you get when going to standby.  You cut the HV and there is a big change in the magnetic field around your HV source wire that those signal wires pick up and amplify before the rest of the DC drains from the system.   

[trobbins]

Perhaps at least rewire the PT HV CT to just go to the first filter cap, and then back to a star 0V.  Similarly, take B+ from the first filter cap, not the diodes.  Look up the excellent schematics showing 0V grounding around first filter layout from the likes of RG Keen and Merlin.


After that, it probably gets harder to diagnose for anyone without time up their sleeve - perhaps then look up ways to diagnose where hum is coming from - eg. get an AC meter on the output and check levels with pot settings, and with various stages with AC shorted signal inputs.

[Toxophilite]

I'm curious as to your grounding scheme, Is everything running back to the same star point at the PT lug?


On my builds I had bad hum if I didn't separate the preamp and the power amp grounds


preamp grounded at the input jack
power amp grounded at the PT lug


This made a huge difference in hum


Also I'm curious as to the picture 'ground 3'  It looks like there is a brown cap with one lead just touching the back of the pot Is that right?


Are your preamp tubes new? a bad tube could cause a whistling


I think having the power supply near the inputs is pretty unconventional, that's an area which is VERY sensitive to noise, could you move that board to an external doghouse ala the blackface later amps?


THat's all I can think of with my limited knowledge


And this is a nice looking build

[uki]

I'm curious as to your grounding scheme, Is everything running back to the same star point at the PT lug?

Almost everything is going to the PT lug, there are grounding at the back of the pots(more about this ahead).

preamp grounded at the input jack
power amp grounded at the PT lug
This made a huge difference in hum

So saparete the ground by section of the amp?

Also I'm curious as to the picture 'ground 3'  It looks like there is a brown cap with one lead just touching the back of the pot Is that right?

It is soldered there, I used the back of the pots to ground those capacitors, because the pots' back are all grounded, there is more like this in all pots. This is bad right  ?

Are your preamp tubes new? a bad tube could cause a whistling

All tubes are new, I thought about that too, I'm going to switch tubes to see what happen.

I think having the power supply near the inputs is pretty unconventional, that's an area which is VERY sensitive to noise, could you move that board to an external doghouse ala the blackface later amps?

Yeah bad layout, Inexperience paid its price here, too much inthusiasm and not enough knowledge. 
There is no way around moving the filter caps to the botton of the chassis in this case ?

THat's all I can think of with my limited knowledge
And this is a nice looking build

Tell me if any more info would help,
Thanks a lot  Toxophilite

@Paul1453  Thanks for the tips!
@trobbins I'm no so sure about what you are saying, but I'll keep that in mind(my electronic knowledge is limited), Many Thanks for the reply !!

I still would like very much to hear from those that have large experience with amps their sincere thoughs about this layout and everything else, I want to get this working properly, for me this is a dream comming through, Fender amps like this, down here in South America cost over 10 grands and this kind of price is for a 50watts or less, I couldn't afford to pay so much for it, so building was the only way to have a decent Fender amp and it did cost much much less, than the prices you are about to see in the following links.
Here is the reality:
http://www.playtech.com.br/combo-guitarra-fender-68-custom-twin-reverb-32125.aspx/p?gclid=CLaDtrvBg8kCFQYJkQodSGIP2w
https://www.madeinbrazil.com.br/combo-fender-59-bassman-ltd-para-guitarra,product,11714,515.aspx
Here is a small 40w amp:
https://www.madeinbrazil.com.br/combo-pguitarra-hot-rod-iii-deluxe-se-2340200900,product,38248,515.aspx

[Paul1453]

@Paul1453  Thanks for the tips!
[/quote]

Just checking to verify you see the 3 green wires going to your pots I'm talking about?  I definitely think those unshielded signal wires running so close to other power wires is at least part of the hum problem you are experiencing.  A simple troubleshooting test.  Strum a chord, switch to standby.  After the POP, is the hum gone as the chord fades away?  If not, you still have your unshielded signal wires, or something else, picking up hum from your AC heater circuit.       Best regards.

[uki]

Just checking to verify you see the 3 green wires going to your pots I'm talking about?  I definitely think those unshielded signal wires running so close to other power wires is at least part of the hum problem you are experiencing.  A simple troubleshooting test.  Strum a chord, switch to standby.  After the POP, is the hum gone as the chord fades away?  If not, you still have your unshielded signal wires, or something else, picking up hum from your AC heater circuit.       Best regards.

Thanks Paul ! I will check that too, making a todo list. Did you see the prices down here ??! OUCH !!

I still would like very much to hear from those that have large experience with amps their sincere thoughs about this layout and everything else, I want to get this working properly, for me this is a dream comming through, Fender amps like this, down here in South America cost over 10 grands and this kind of price is for a 50watts or less, I couldn't afford to pay so much for it, so building was the only way to have a decent Fender amp and it did cost much much less, than the prices you are about to see in the following links.
Here is the reality:
http://www.playtech.com.br/combo-guitarra-fender-68-custom-twin-reverb-32125.aspx/p?gclid=CLaDtrvBg8kCFQYJkQodSGIP2w
https://www.madeinbrazil.com.br/combo-fender-59-bassman-ltd-para-guitarra,product,11714,515.aspx
Here is a small 40w amp:
https://www.madeinbrazil.com.br/combo-pguitarra-hot-rod-iii-deluxe-se-2340200900,product,38248,515.aspx

[Paul1453]

I can't afford the prices here in the US, and don't really want to see how much more they rape you for down there.  But I'll take a look.  That is why I try to salvage/scavenge most of my parts.   

[Toxophilite]

I'm one of the less experienced on this forum, though I have built a few amps, with help from the folks here.


I too build my own amps because I an't afford to buy them


regarding your power supply(filter cap board)(and I could be wrong about this some chime in if I am)
Is there no room on the outside of the chassis to mount the board, run the wires through a few grommeted holes and then have a small metal box covering them?


Could you put a busbar(long thick copper wire) behind the pots and solder all the grounds to it and have it ground at the input jack?


I asked about the cap because that sort of attachment(end of wire to flat surface) doesn't look too strong


I'm really hoping someone  lot more experienced than me will jump in but I'm betting a lot of your hum could be grounding


All the best!

[uki]

I'm one of the less experienced on this forum, though I have built a few amps, with help from the folks here.

Still you are probably much more than I am !!   

regarding your power supply(filter cap board)(and I could be wrong about this some chime in if I am)
Is there no room on the outside of the chassis to mount the board, run the wires through a few grommeted holes and then have a small metal box covering them?

Maybe that could be possible the space is very tight, I got a picture of that side of the chassis with a piece of paper simulating the power supply.
Maybe could spin the choke to fit the power supply, or is that a bad idea ? Tell me what do you think.

Could you put a busbar(long thick copper wire) behind the pots and solder all the grounds to it and have it ground at the input jack?

You are probably talking about what is shown in this link: http://el34world.com/charts/grounds.htm
And yes I will do that.
My thoughts was if the back pots are touching the chassis then I could use them as ground points, is that bad ? 

I asked about the cap because that sort of attachment(end of wire to flat surface) doesn't look too strong

All solders on pots are well done. But, is that a good or bad practice to do the groundings there ?

I'm really hoping someone  lot more experienced than me will jump in but I'm betting a lot of your hum could be grounding

All the best!

You are a great help Toxophilite THANKS, and I'm taking notes about all your guidance, from the others too.
Been learning tons from you guys!

I just want to hear the thoughts of those that are very experienced with amps, If it is really possible to fix all that AC close to the signal wires, only now on this thread I've grasp what is going on with the amp(bad layout). Also I been thinking if it is not fixable, I got the idea to remove the vibrato(don't really need or want it) and maybe the second channel too making a much smaller circuit board putting it alway from all the AC, that would also give me 3-4 spare tubes and components, yet before taking that extreme decision and change, the comments of those that have large experience would be very much helpfull. The amp works for the most part, one important thing I forgot to mention it worked with a 250mA fuse all the time in the 3-4 powers it had so far without getting blowed. Is that a good thing ?


Thank you in advance !

[Willabe]

Slow down and think about it some more and wait for any more input before you start tearing things out. 

[Toxophilite]

+1 on that
I was just making suggestions from my limited experience but ideally you should wait for more experienced people to chime in

[trobbins]

Recommended learning curve:
 R.G.Keen's article on grounding.  http://www.geofex.com/Article_Folders/star%20grounding%20amps.pdf
  Merlin Blencowe’s article on grounding.  http://www.valvewizard.co.uk/Grounding.pdf


RG's schematic has a few inconsistencies, but is 99% a good target.

[uki]

I'm waiting, not doing anything without knowing exactly what to do. Thanks for the advice guys.

Recommended learning curve:
 R.G.Keen's article on grounding.  http://www.geofex.com/Article_Folders/star%20grounding%20amps.pdf
  Merlin Blencowe’s article on grounding.  http://www.valvewizard.co.uk/Grounding.pdf
RG's schematic has a few inconsistencies, but is 99% a good target.

  Thanks for the links ! 1st paper is contradictory thou where it says to not solder a bus in the back of the pots, but that looks like depend on the amp in question.
I've download the 2nd paper already but they are slitghly different, same paper different versions, there are some differences between the 2.
Some of you might be interested.

[Willabe]

1st paper is contradictory thou where it says to not solder a bus in the back of the pots,

Technically it is a ground loop soldering to the back of the pots. But, it is a small loop with not as much current as the output tubes and their filter caps flowing through it.

Look in Doug's library of tube amp information (link found at the very bottom of any page in the forum) and study his grounding scheme. It works, proven here many times by many guy's on many builds.

Doug separates the high current B+ grounds, ie, power tubes/filter caps from the low current B+ preamp tubes/filter caps.

If it was my amp the 1st thing I'd try is like Doug shows in his library. Then go from there. It might be all you need.

but that looks like depend on the amp in question.

No, I don't think that's why.

I've download the 2nd paper already but they are slitghly different, same paper different versions, there are some differences between the 2.

With the free on line info at Merlin's web site there's sections missing from his books. And with the web site he can change/update the info as he want's/needs to for what ever the reasons.

I'd probably go with the latest info from him and not the earlier writings. 

[Toxophilite]

There does seem to be many different possible grounding schemes that work


Separating the power amp from the preamp like Doug does does seem to help a lot and is relatively easy/non-destructive to implement


Apologies I should looked closer at the exterior of your chassis before suggesting mounting a cap doghouse on it

[PRR]

Your High Volt PT winding has three leads. On Fender they are Red-Red-Red-Yellow; yours seems to be plain Yellow.

Where does that (Red)Yellow wire go?

It MUST go direct to the first filter cap "-" leg.

It seems to snake off in the other direction and get lost?

That wire has BIG current spikes. If it goes anyplace except the first filter cap, it will inject buzz everywhere.

Grey cases. Hoffman returns the yellow, the first-cap, and all other grounds to one transformer bolt. This works because the resistance of the bolt is very-very small, the BIG current spikes induce very-very small buzz, he does not have a problem. There are other variations which "do work". However since you have buzz, I would trace that wire and wonder what trouble it may be injecting along the way.

[uki]

Your High Volt PT winding has three leads. On Fender they are Red-Red-Red-Yellow; yours seems to be plain Yellow.

Where does that (Red)Yellow wire go?
It MUST go direct to the first filter cap "-" leg.

I got 3 wires going to the diodes red red and yellow, green green going to pilot lamp and then heaters, black and blue going to ground transformer bolt, I've followed what is in the schematic, the colors are not exact as they should be, seen like they are:
Red-Blue = Yellow
Red-Yellow = Blue
Green-Yellow = Black

Confusing I know , the makers have flipped the colors.

It seems to snake off in the other direction and get lost?
That wire has BIG current spikes. If it goes anyplace except the first filter cap, it will inject buzz everywhere.

Grey cases. Hoffman returns the yellow, the first-cap, and all other grounds to one transformer bolt. This works because the resistance of the bolt is very-very small, the BIG current spikes induce very-very small buzz, he does not have a problem. There are other variations which "do work". However since you have buzz, I would trace that wire and wonder what trouble it may be injecting along the way.

Yea things looks a bit confusing there, I will arrange that better it isn't totally done yet, some wires from PT still too long(this maybe one source of the buzz?), also I'll probably flip the rectifier board 90° so the red 330v wires get alway a lil more from the pots.
So one of those wires or black or blue should then go to the 1st filter cap "-" leg , is that cap the one also receiving the stanby switch and one leg of the choke ?  Ok what is the trick with that? How does it work , what changes instead of sending that wire directly to the transformer bolt? Aren't the "-" legs of the filter caps going to that bolt too ?   

The presence pot wire going from the pot to the circuit board is going around the PT and in the other side the wire going to the speaker jack, it is just beside the PT primary, that is a big problem yes? So shield those two wires ?

Another thing I been told about is: the wires to ground from the circuit board they are in a bus and then going to the transformer bolt, I know already that they have to be separated but where to send them? To the back of the pots bus?

Here a picture of those wires and PT schematic.

Thanks tons PRR for the insights !!

[PRR]

> red 330v wires get alway a lil more from the pots.

I missed that, but it is a very likely part of the problem.

[birt]

those red wires also go under the board close to signal wires. go over it and keep them short. if you want to have them longer (for future re-use or whatever) have all the excess wire at the transformer itself, away from boards and signal paths.


use shielded wire for your inputs, they are crossing the psu caps board. (shield grounded on 1 side!)


i would also try to make the black/white mains wires follow the chassis as tight as possible. i'd probably tape it in the folded edge of the chassis with aluminum tape.


your layout would make much more sense if the pots were on the side of the tubes.
i tend to keep high voltage and AC wiring as far as possible from signal wire, especially preamp wiring. like crossing them at minimal points instead of running them parallel. thinking in 3 dimensions and keeping them bottom or top in the chassis... and good grounding. i've used star grounding, a ground buss for each section combined in a star and variations on that. i don't trust the backside of pots for a good ground and i'm very paranoid about grounding but many commercial amplifiers have proved in the past that you might be able to get away with pretty shitty grounding schemes.
this is a good read as well: http://www.valvewizard.co.uk/Grounding.pdf


but if my own 'layout rules' are not possible i've resorted to "excessive" shielding. like metal plates bolted or riveted to the chassis separating sections of the circuit. shielding multiple wires together using braided wire 'socks' taped to the chassis with aluminum tape. i've done this with mains wiring instead of shielding all the wires around it. drilling holes in the chassis to have certain wires run over the outside avoiding parts of the circuit... i guess this is not good design practice but some situations make you get creative. it might work for you too.




this is the messiest one i guess. all connections are on the same front panel and the PT is in the back, so you in the left and right of the chassis you can see the mains and standby wiring going through these "socks". there is a metal plate around the power and standby rotary switch. part of the tone stack is on the outside of the chassis because the controls are there. there is shielded wire used on the input as well.

[uki]

those red wires also go under the board close to signal wires. go over it and keep them short. if you want to have them longer (for future re-use or whatever) have all the excess wire at the transformer itself, away from boards and signal paths.


use shielded wire for your inputs, they are crossing the psu caps board. (shield grounded on 1 side!)


i would also try to make the black/white mains wires follow the chassis as tight as possible. i'd probably tape it in the folded edge of the chassis with aluminum tape.


your layout would make much more sense if the pots were on the side of the tubes.
i tend to keep high voltage and AC wiring as far as possible from signal wire, especially preamp wiring. like crossing them at minimal points instead of running them parallel. thinking in 3 dimensions and keeping them bottom or top in the chassis... and good grounding. i've used star grounding, a ground buss for each section combined in a star and variations on that. i don't trust the backside of pots for a good ground and i'm very paranoid about grounding but many commercial amplifiers have proved in the past that you might be able to get away with pretty shitty grounding schemes.
this is a good read as well: http://www.valvewizard.co.uk/Grounding.pdf


but if my own 'layout rules' are not possible i've resorted to "excessive" shielding. like metal plates bolted or riveted to the chassis separating sections of the circuit. shielding multiple wires together using braided wire 'socks' taped to the chassis with aluminum tape. i've done this with mains wiring instead of shielding all the wires around it. drilling holes in the chassis to have certain wires run over the outside avoiding parts of the circuit... i guess this is not good design practice but some situations make you get creative. it might work for you too.




this is the messiest one i guess. all connections are on the same front panel and the PT is in the back, so you in the left and right of the chassis you can see the mains and standby wiring going through these "socks". there is a metal plate around the power and standby rotary switch. part of the tone stack is on the outside of the chassis because the controls are there. there is shielded wire used on the input as well.

Hey thank you very much for the reply ! Those seen to be great Tricks, so you put a plate close to the PT ? Is that thick shielded wire the main AC input ? I see the idea and looks good anything that help get rid of the hum helps !!

Your High Volt PT winding has three leads. On Fender they are Red-Red-Red-Yellow; yours seems to be plain Yellow.

Where does that (Red)Yellow wire go?

It MUST go direct to the first filter cap "-" leg.

Please explain what is the trick with that connection, as far as I understand the filter cap "-" leg is going to the same transformer bolt as this wire is already, what changes ? Does it get grounded differently ? Thanks in advance!

[Willabe]

Your High Volt PT winding has three leads. On Fender they are Red-Red-Red-Yellow; yours seems to be plain Yellow.

Where does that (Red)Yellow wire go?

It MUST go direct to the first filter cap "-" leg.

Please explain what is the trick with that connection, as far as I understand the filter cap "-" leg is going to the same transformer bolt as this wire is already, what changes ? Does it get grounded differently ? Thanks in advance!

Uki, it's explained in Merlins grounding info and he has drawings of it.

[Willabe]

Those seen to be great Tricks, so you put a plate close to the PT ? Is that thick shielded wire the main AC input ? I see the idea and looks good anything that help get rid of the hum helps !!

Adding a metal shield and/or things like shielding to the AC power wires are not the 1st things to go to in trying to eliminate hum in and amp. They are mostly used as a last resort when other attempts have failed. 

[sluckey]

It's important that the filter caps for the power amp be connected directly to the HT center tap lead. This is usually done at a PT bolt. It's also important that the filter caps for the preamp to NOT be connected to the power amp ground, especially in the case you have where a single ground wire connects ALL of your filter caps to the PT bolt. The power amp caps put big dirty stuff on that single ground wire and it will show up in the preamp because the caps for the preamp share that same ground wire. The answer is to separate the power amp ground and the preamp ground.

Fender did this on the original 6G8. It's hard to see on the layout, but if you look closely you'll see two grounds coming from the cap board. I've circled them in red on the attached pic.

So, separate your grounds. Cut the ground buss at the "X" on the pic. Leave your gray ground wire (this is now part of your power amp ground) connected to the PT bolt. Insure that the PT center tap is connected to this same bolt. Now drill a small hole and install a screw/nut near your input jacks and connect the right end of the cap board ground buss to that screw. This becomes part of the preamp ground.

Hopefully this will help with the hum issues. I see several other issues also but they will not be so easy to correct. Make this simple ground change first to see if it helps. Then I'll discuss the other issues I see.

[uki]

@Willabe thanks for the hints, I'll do 1st things 1st and progress on the fixing as sugested, I'm still reading the grounding doc.
Actually I've been reading lots of things about tube amps..

It's important that the filter caps for the power amp be connected directly to the HT center tap lead. This is usually done at a PT bolt. It's also important that the filter caps for the preamp to NOT be connected to the power amp ground, especially in the case you have where a single ground wire connects ALL of your filter caps to the PT bolt. The power amp caps put big dirty stuff on that single ground wire and it will show up in the preamp because the caps for the preamp share that same ground wire. The answer is to separate the power amp ground and the preamp ground.

I did seen some on that but I didn't understand before why, now I know that it is important to saparete those caps grounds.

Fender did this on the original 6G8. It's hard to see on the layout, but if you look closely you'll see two grounds coming from the cap board. I've circled them in red on the attached pic.

I had no clue  about that! Thanks for clarifying this.

So, separate your grounds. Cut the ground buss at the "X" on the pic. Leave your gray ground wire (this is now part of your power amp ground) connected to the PT bolt. Insure that the PT center tap is connected to this same bolt. Now drill a small hole and install a screw/nut near your input jacks and connect the right end of the cap board ground buss to that screw. This becomes part of the preamp ground.

Hmmm I think that will be a bit more than that, I did switch the order of the caps to have the resistors legs all sodered to the next one(got pictures and schematics), and not having one floating around, I think I'll have to do 2 or 3 cuts and link the power cap ground in the middle to the ones in the edge, check out the pics, and also by looking at it I found something that maybe a mistake, the choke is connected directly to the stanby switch and the OT center wire also is connected there, could it be the source of the pop noise when turning the stanby switch off?

Hopefully this will help with the hum issues. I see several other issues also but they will not be so easy to correct. Make this simple ground change first to see if it helps. Then I'll discuss the other issues I see.

Thanks tons sluckey, I'll do 1st things 1st and then procede from there.

Ok here is the pics, A is what it should be, probably. B is how I did it. (the PS board schematic was done by Pete or DummyLoad (thanks)).

[sluckey]

I would personally rewire the cap board as per drawing A. However, here's a simple mod to drawing B that will separate the grounds with minimum rewiring. Should be fairly easy. Give this a try. If the hum improves, consider rewiring the board as per drawing A.

[uki]

I would personally rewire the cap board as per drawing A.

Thanks Sluckey, I did A to get things right.

I got questions:
-> About the ground wires comming from the main board, there are 5 of them, I did at 1st a buss and send all of them to the transformer bold(removed it already), I know it was a bad choice because the guy that helped me with the 1st power up told me to change that, so I'm doing it but I don't know what is the best way, are there preamp and power sections of those wires, can the sections be put in separated busses or in busses at all, or they must go to ground with separated wires? I did look at the grounds doc but I'm still in doubt about how to do it http://el34world.com/charts/grounds.htm

-> The pots, do they must have a buss soldered in the back or just touching the chassis works ? (as is now the back of the pots are closing circuit with the chassis)
 
Got pics.

[Willabe]

You have ground loops set up with the way you daisy chained the grounds on the cap board AND daisy chained the grounds on the turret/eyelet board AND then ran a wire from each filter cap ground end to each ground star connection on the turret/eyelet board.

Look at Sluckey's drawing and look at my drawing below. Ground loops are red arrows. To many/multiple paths for the ground to flow through.

You should remove the daisy chain on the turret/eyelet board, purple in my drawing. This will break the loops and the circuit grounds will now have only 1 path to ground.

 

[Willabe]

Or, like this;

[uki]

You should remove the daisy chain on the turret/eyelet board, purple in my drawing. This will break the loops and the circuit grounds will now have only 1 path to ground.

Thanks Willabe,
When you say turret/eyelet board you mean the main circuit board yes?
Are you referring to the black wire in the picture, same as purple in your draw ?
If that is what your are talking about, it was already removed(it was just sitting there when I took the pic),
I see your are pulling wires from those points, to the minus legs of the filter caps, but there are 5 of them,
do they all go to the minus legs of the pre-amp section of the filter caps ?

[Willabe]

When you say turret/eyelet board you mean the main circuit board yes?

Yes.

Are you referring to the black wire in the picture, same as purple in your draw ?

Yes.

I see your are pulling wires from those points, to the minus legs of the filter caps, but there are 5 of them,
do they all go to the minus legs of the pre-amp section of the filter caps ?

There's 2 basic ways you can run these grounds, 1. like Merlin in the ground loop 2 drawing, 2. Like Doug in the ground loop 3 drawing.

Look at them again. 

[Willabe]

I see your are pulling wires from those points, to the minus legs of the filter caps, but there are 5 of them,
do they all go to the minus legs of the pre-amp section of the filter caps ?

I only drew out 3 gain stages with 3 B+ filter caps as an example.

In 1 of your pictures you 5 ground(?) wires numbered. Each of those ground wires are going from the main circuit board to the B+ filter cap board, each ground wire going to a single filter cap's ground end? Like in the groung loop 3 drawing?   

[Willabe]

Merlin points out in his grounding info about the circuit grounds from the gain stage(s) goes back/is grounded to the B+ filter cap's ground end of the filter cap that supplies the B+ for that gain stage. This forms a ground star. Then he runs a wire from that ground star to the next ground star. Look at Merlins drawings.

This daisy chain string of ground stars gets grounded to the chassis with a single wire from the ground star string to the chassis.

Sluckey showed you how to separate the power tubes chassis ground connection from the preamp chassis ground connection so the heavy/noisy power tube ground current doesn't get picked up by the preamp tubes grounds.   

[uki]

... Like Doug in the ground loop 3 drawing.

Look at them again.

I did look at them again and the answer looks to be yes.

In 1 of your pictures you 5 ground(?) wires numbered. Each of those ground wires are going from the main circuit board to the B+ filter cap board, each ground wire going to a single filter cap's ground end? Like in the groung loop 3 drawing?   

I had those 5 wires soldered to that black buss wire before, but going to the transformer bolt, would that cause the hum?
I've been told to separate those five wires, like in your ground loop 2 drawing, would that be a better choice ? Or is the ground loop 3 drawing type better ?

Merlin points out in his grounding info about the circuit grounds from the gain stage(s) goes back/is grounded to the B+ filter cap's ground end of the filter cap that supplies the B+ for that gain stage. This forms a ground star. Then he runs a wire from that ground star to the next ground star.

This daisy chain string of ground stars gets grounded to the chassis with a single wire from the ground star string to the chassis.

Oh I think I got this, sounds like a stair of grounding scheme, like going down step by step in a stair.

Sluckey showed you how to separate the power tubes chassis ground connection from the preamp chassis ground connection.

Yes I did that in the filter caps board.

Ok I think I got the groundings of this part at least, I'm also remaking the diode board to it have a little more distance from the pots, also going to rewire the pots in that area taking the wires away from the diodes board. Once that is done then turn up the amp and see what happens to the hum.
   

[Willabe]

Sluckey showed you how to separate the power tubes chassis ground connection from the preamp chassis ground connection.

Yes I did that in the filter caps board.

What happened? Did it make a difference in hum?

[uki]

Sluckey showed you how to separate the power tubes chassis ground connection from the preamp chassis ground connection.

Yes I did that in the filter caps board.

What happened? Did it make a difference in hum?

I'm still working on the amp, can't turn it on yet, the diode board is out, I'm remaking it. I'll post news as soon as it is done.

[Willabe]

When your trying to track down a source of hum you want to try 1 thing at a time. That way you'll know what caused the hum.

[Willabe]

Don't for get this;

Your High Volt PT winding has three leads. On Fender they are Red-Red-Red-Yellow; yours seems to be plain Yellow.

Where does that (Red)Yellow wire go?

It MUST go direct to the first filter cap "-" leg.

It seems to snake off in the other direction and get lost?

That wire has BIG current spikes. If it goes anyplace except the first filter cap, it will inject buzz everywhere.

Grey cases. Hoffman returns the yellow, the first-cap, and all other grounds to one transformer bolt. This works because the resistance of the bolt is very-very small, the BIG current spikes induce very-very small buzz, he does not have a problem. There are other variations which "do work". However since you have buzz, I would trace that wire and wonder what trouble it may be injecting along the way.

[uki]

When your trying to track down a source of hum you want to try 1 thing at a time. That way you'll know what caused the hum.

OH!! That is totaly true, ok I wont change anything else yet but those grounds.

[uki]

The changes on the grounding are done as suggested by Willabe. But the hum persist at the same amount.
Ok what next ?

[Willabe]

Which changes?