SluckeyAmps 1960 Vox AC15 Build

[SkipJohnson]

What is the ground for in the red circle? 

Exactly how many ground connections to the chassis do you have, 2, 3, 4, 5?

That was Ground Scheme 1.2 (i.e. part of a partial implementation og Slucky's suggested changes to the grounding scheme).
I later re-did the entire ground scheme (GS 2.0), this chassis ground connection is no longer there.

[SkipJohnson]

Exactly how many ground connections to the chassis do you have, 2, 3, 4, 5?

Four as follows:
1) AC Power Cord Ground
2) Power Amp Ground
3) Control (Preamp) Ground #1 (volume pots)
4) Control (Preamp) Ground #2 (Effects and inputs)

[SkipJohnson]

Can we see some pictures of the whole amp, inside? And I'd like to see where the speaker jacks are and whats next to them.

And some pics of the back side of the chassis, showing the PT/OT?

Will do. 
I have been trying to catch up on all the replies on this thread, and I need to complete the power section changes you suggested first.
Pictures will be later today.
thx!!!!!!

[Willabe]

3) Control (Preamp) Ground #1 (volume pots)
4) Control (Preamp) Ground #2 (Effects and inputs)

Chassis grounds 3 and 4 should be combined together into 1 ground.

[SkipJohnson]

Can we see some pictures of the whole amp, inside? And I'd like to see where the speaker jacks are and whats next to them.

And some pics of the back side of the chassis, showing the PT/OT?

Will do. 
I have been trying to catch up on all the replies on this thread, and I need to complete the power section changes you suggested first.
Pictures will be later today.
thx!!!!!!

Pictures are ready for viewing at:
https://www.flickr.com/photos/23805934@N02/albums/72157690742479393

[SkipJohnson]

3) Control (Preamp) Ground #1 (volume pots)
4) Control (Preamp) Ground #2 (Effects and inputs)

Chassis grounds 3 and 4 should be combined together into 1 ground.

I'll work on that.

[sluckey]

What is the ground for in the red circle? 

Exactly how many ground connections to the chassis do you have, 2, 3, 4, 5?

That was Ground Scheme 1.2 (i.e. part of a partial implementation og Slucky's suggested changes to the grounding scheme).
I later re-did the entire ground scheme (GS 2.0), this chassis ground connection is no longer there.

Why did you remove that ground connection? SEE PIC...

[SkipJohnson]

What is the ground for in the red circle? 

Exactly how many ground connections to the chassis do you have, 2, 3, 4, 5?

That was Ground Scheme 1.2 (i.e. part of a partial implementation og Slucky's suggested changes to the grounding scheme).
I later re-did the entire ground scheme (GS 2.0), this chassis ground connection is no longer there.

Why did you remove that ground connection? SEE PIC...

Both the terminal strips are connected directly to the chassis now, NOT isolated.  Per Willabe I plan to combine these into a single terminal strip near the input jacks (where the 5 lug is now).

[sluckey]

Are all the lugs on those terminal strips strapped together?

[Willabe]

Sluckey meant to run the OT secondary wire around the end of the board, not all the way around to the chassis end.

Now you have that wire laying on the ac power and other things.

[SkipJohnson]

Are all the lugs on those terminal strips strapped together?

Yup

[SkipJohnson]

Sluckey meant to run the OT secondary wire around the end of the board, not all the way around to the chassis end.

Now you have that wire laying on the ac power and other things.

OK.  I'll fix that.

[sluckey]

Has anything you have done today affected the top cut hum issue?

[SkipJohnson]

Nope 
I re-re-routed the yellow OT wire around the board instead of the end of the chassis.
I am in the middle of changing the two control ground terminal strips into one 7 lug under the input jacks.

[sluckey]

Measure resistance from pin 2 of each EL84 to chassis. What do you have?

[SkipJohnson]

Measure resistance from pin 2 of each EL84 to chassis. What do you have?

Finished re-working the preamp ground from two terminal strips to one.  Stay tuned for results (things have changed for the better).  I will post results when I complete a set of tests.

Here are the EL84 Pin 2 resistance readings:  221k ohms on both tubes.

[shooter]

since ur testing.............
play something;
remove the cap on the PA tubes cathode, play again;
Did the hum decrease with overall gain drop from pulling cap?

add a BIG cap, something 2, 3 X's bigger, gatorcippin is fine
any change

[SkipJohnson]

since ur testing.............
play something;
remove the cap on the PA tubes cathode, play again;
Did the hum decrease with overall gain drop from pulling cap?

add a BIG cap, something 2, 3 X's bigger, gatorcippin is fine
any change

Hold that thought...……………
As I said, things have changed.  I am methodically testing and documenting and will post in a bit.

[SkipJohnson]

I completed all the changes discussed over the las couple of days including re-working the preamp ground from two terminals to one.
The result of this last change or a combination of the recent changes is that the HUM is gone!!!!!   

I have performed a series of tests.  The details can be viewed in the attached Test Notes.PDF file.

Bottom line is I have a couple issues to address as follows:
   1) Major Items
      a. Effects Not Working
   2) Minor Items
      a. Some Nor/Vib Vol Noises
         i. The noises are eliminated by setting the Top Cut above 2.5
         ii. This is similar Top Cut behavior when the loud Hum issues was present

I think the effects issue will be solved fairly easily as they worked before I did a last few changes, so I (think I) know where to focus.
The other Volume related noises are a nuisance and seem related to the gremlin we have been chasing.  But I'll keep working it.

Thanks for all the help so far EVERYONE, especially Slucky and Willabe.  REALLY appreciate it.


 

[SkipJohnson]

BTW: I think that the one change I made that might be the fixer was moving the PI ground from the power amp ground to the preamp ground.

[shooter]

 
gonna  for a quick clarification
Since PP PA's tend to noise cancel, would the "sharing" of cathode parts "lessen" that cancelation 

thanks

[Willabe]

gonna  for a quick clarification
Since PP PA's tend to noise cancel, would the "sharing" of cathode parts "lessen" that cancellation 

That's a good question.

I would think no.   

[sluckey]

PP PAs have common mode rejection due to the OT. This means that if the same signal appears on both inputs that signal will be cancelled in the OT. That same signal might be power supply hum. Or it might be some other stray signal/noise picked up in the air. But for it to cancel it must appear on the top and bottom of the OT. For it to cancel perfectly, it must be identical. This is one reason that it's important to have equally balanced tubes and perfect OTs. I don't think a properly bypassed cathode resistor will be a factor.

[SkipJohnson]

OK, back at the bench.
I found the issue with the effects not working.  As soon as I looked at that area closely I saw that I have the depth pot slights twisted off center, causing the resister between the speed and depth pots to make contact with the right post of the depth pot.  A quick straightening of the depth pot corrected the situation.

So the only remaining issue is the minor Volume Pot noises.  With the top cut turned up past 2.5, these are eliminated.
I am calling it good until someday these bother me enough to dive in some more.

Thanks for everyone's help.  You all have been super helpful and relentless.  I hope I can be as helpful to someone with issues I can help with.

[sluckey]

You really did a super job on this project. I hope you enjoy it. I know Ed's gonna start talking Celestion Blue so I'll kick it off for him. They are pricey but they bring out a lot of good in this amp, especially the EF86 channel.

[SkipJohnson]

You really did a super job on this project. I hope you enjoy it. I know Ed's gonna start talking Celestion Blue so I'll kick it off for him. They are pricey but they bring out a lot of good in this amp, especially the EF86 channel.

I was going to put this atop my Fender Custom Shop 2x12, but I like the idea of a speaker that is "One of the most famous speaker voices of all-time, helping to define the '60s British Invasion".  Just ordered one on Amazon that will be here on Sunday.
Thanks again!!!!!

[ElusiveMoose22]

Glad you got everything squared away finally!  Way to stick it out and trouble shoot that hum 
Any vids or audio of what this thing sounds like now that you're done?  Let us bask in the glory of that classic EL84 overdrive lol
Also I'm curious how your EF86 channel sounds.  Working on an amp project with EF86's in the preamp myself right now and I'm curious how other people are finding the sound to be in their amps.

[SkipJohnson]

Finished my head and speaker cabinets today.
Amp - https://www.flickr.com/photos/23805934@N02/47567024481/in/dateposted-public/
Head - https://www.flickr.com/photos/23805934@N02/47567023881/in/dateposted-public/
Speaker - https://www.flickr.com/photos/23805934@N02/47567023831/in/dateposted-public/
Celestion Blue - https://www.flickr.com/photos/23805934@N02/47567024071/in/dateposted-public/

Sounds amazing.  The normal channel is really loud, responsive and the overdrive is awesome.  The Vib channel is also great.  Alot less volume, but the analog vib/trem effects sound great.
I am used to the vintage Fender amps I have been building, what a difference.   I still like the Fender sound, but this is really a different ballgame.

I also tried plugging the amp into my Genz Benz 2x12 speak cab.  Sounds really different, but it is a ported cabinet.  The G/B sounds bigger, the Celestion Blue (in a sealed cab) sounds a lot tighter.

Anyway, I am really glad I did this project.  I love the amp, I learned a ton and REALLY appreciate and respect the folks who helped me out begugging this beast.

Glad you got everything squared away finally!  Way to stick it out and trouble shoot that hum 
Any vids or audio of what this thing sounds like now that you're done?  Let us bask in the glory of that classic EL84 overdrive lol
Also I'm curious how your EF86 channel sounds.  Working on an amp project with EF86's in the preamp myself right now and I'm curious how other people are finding the sound to be in their amps.

I'll see about posting some video, I am relatively shay about my playing So I'll see.
As for the EF86 channel, it is nothing like the Fenders I have been building.  As I said above, this thing is really loud, responsive and overdrives really early when [playing with a heavy hand, and clean when lightening up the play.
In my opinion, you cannot go wrong with the EF86.

[sluckey]

Very nice! I like putting the chassis on display in that head.