AB763 Deluxe Lite build.

[sluckey]

Did you purposely omit one of the bias caps?

[Papa Jim]

Did you purposely omit one of the bias caps?

Did you not see post #49
Ya see that light. I got filaments. 
I do know what I'm doin.....I did get a light!!!!!
I do know what I'm doin.....Well maybe!!!!!!
I do know what I'm doin.....NOT!!!!!
 

[sluckey]

Did you purposely omit one of the bias caps?

Did you not see post #49

Yes I did. It has nothing to do with my question so I repeated the question because you did not read it correctly. You asked to look over your schematic and I did. I saw the missing cap and asked the question. Now once more...

Did you purposely omit one of the bias caps?

Just messing with you. I see you do have two bias caps on the board.   

[Papa Jim]

Duuhh. Have I ever said the board was done.  Besides Bias and PT are kinda the same thing.....Are they not?...

Is this better. C17 added to the schematic to match what has been on the board for several days now.. 

[sluckey]

Now was that so hard?   

[Papa Jim]

Not too bad. 

[sluckey]

Don't know if you have noticed but a real Fender AB763 only has one bias cap. They started using two caps later when they switched to that funky bias balance pot that had a center tap in addition to the normal three lugs.

[Papa Jim]

Did not notice that. I read about that funky pot not long ago. Glad this design doesn't have one.

[Tony Bones]

Is there room for another cap at the top of R35? Two RC stages of filter for the bias supply is a good idea.

[sluckey]

 déjà vu     

[Papa Jim]

There's plenty of room but I really want to build it as is first before doing any mods.

[Papa Jim]

Thanks but I'm sure if it needed that Sluckey would have added it. IMHO

[Tony Bones]

Thanks but I'm sure if it needed that Sluckey would have added it. IMHO

He did! it's C17. That's why I gently brought it up. Sluckey's efforts to tell you didn't seem to work.

[Papa Jim]

Sorry Tony Bones. I thought you were talking about something different because I had added C17 back in post #53. Now it makes sense why Sluckey said deja vu. 

[Tony Bones]

Sorry I missed where you added it.

[Papa Jim]

we're even. I missed what you were saying. 

[Tony Bones]

To be honest, I got to the bottom of the first page and thought that it was the end of the thread. I didn't even see the entire second page where Sluckey invested so much effort explaining about the second cap, never mind where you added it. Sorry I'm such a dope sometimes... 

[Papa Jim]

Filament artificial ground 100R's connect to gnd buss at Amps input jack end or the output  end of the buss? Using a single point with buss connected to chassis at the input jack.

[shooter]

the output  end of the buss

If the tranny had a CT, I believe it's typical to ground at the dirty end.  You don't want a 3VAC signal too close to a 20mVAC input

[Papa Jim]

Ok. The PT. Center tap, Filament artificial gnd and the common gnd from all the B+ caps are all close together. I am thinking about connecting them all together at my can caps common terminal and taking one wire to the dirty end of the buss. Here's my changes to the schematic that reflect that.

[sluckey]

I would not put all that dirty stuff on the ground bus that runs behind the pots. I would connect all the dirty to a PT bolt or a dedicated ground lug near the PT. My pot bus is only connected to chassis using a dedicated ground lug near the input jack.

[Papa Jim]

Filament voltages.....Check.
Unloaded B+ Voltages......Check. They are all close to 440 vdc.
Bias voltages tomorrow.....and get started from the input jack onward....

[Papa Jim]

I would not put all that dirty stuff on the ground bus that runs behind the pots. I would connect all the dirty to a PT bolt or a dedicated ground lug near the PT. My pot bus is only connected to chassis using a dedicated ground lug near the input jack.

\
\
Ok. done.

[Papa Jim]

Guess I shoulda looked at your layout Sluckey. 

[Papa Jim]

Close but no cigar.........yet!

[Papa Jim]

So with current limiter did all the voltage pre-checks.
All were as expected.
Turned the bias pot for the most negative voltage.
Put preamp tube in looked good with No Redplating.
Put PI tube in (5751) forgot to order 12AT7. Looked good with No Redplating.
Put both 6V6 output tubes in. No Redplating.
Removed current limiter.
Checked cathode current with Plate to Cathode voltage measuring 439 vdc.
V3 has 20ma.
V4 has 15ma.
For bias pot I didn't have a 10K so I had to put a 25k pot in.
Should I tweak on the plate resistors to get them both at 15ma. which will give me some adjustability for added current with the bias pot.
Oh be the way I strummed the guitar briefly and it amplifies and so far seems really hum quiet.

Pics of the amp and cab. Pic of my mancave closet workshop. Lol

[shooter]

Should I tweak on the plate resistors to get them both at 15ma

If you're talking about the PA tubes, they have no plate R
the math says 439 * .02 = 8.8W which is a good place for fixed bias 6V6(?)

[sluckey]

I'd say you have arrived! That imbalance between the output tubes is due to the tubes. I would just live with it. But you can spend some dollars and roll a bunch of tubes through the amp until you get a perfectly matched set. And two months from now they probably won't still be a perfect match. Let your ears tell you what you think. BTW, there ain't no plate resistors to tweak on to match the tubes. Those tubes are connected to a transformer. 

You know, when I say I'm working in a tight space it usually means I'm in a tweed style chassis. I can see that tight space has a totally different meaning for you!   

I know the feeling. I've been there before.

[Papa Jim]

Yeah, but I wanted plate resistors. Lol. Ok cool, I will just live with it. According to the numbers I punched into some online bias calculators I think I am running at 70% dissapation.
I'm gonna play it for now and see what I think. Thanks guy's for all the help.  It's been quite a lot of fun ribbing each other. 

[Papa Jim]

You know, when I say I'm working in a tight space it usually means I'm in a tweed style chassis. I can see that tight space has a totally different meaning for you!   

Actually I have it made.  I have one side of a 2 car garage loaded with my tools and a workbench but I prefer to work inside. I'm too nosey what's goin on. 
Have been able to play the amp about 10 minutes and Oh My Gosh. It is awesome. I got it going to a Celestion G12M greenback. Now I know what a real amp is supposed to sound like. I've been jacking around with crap for years. Can't wait to get some more time with it. 

[Papa Jim]

I built in 2019 but it is hard to use anything past 1 on the volume pot. That can't be right. What should I look at?

[Ronquest]

I built in 2019 but it is hard to use anything past 1 on the volume pot. That can't be right. What should I look at?

What is your exact schematic?

[Papa Jim]

https://sluckeyamps.com/misc/AB763_Deluxe_Lite.pdf

[Ronquest]

First thought, linear pot vs log on your 1M volume?

[Ronquest]

Also this https://el34world.com/Forum/index.php?topic=21776.0

[sluckey]

First thought, linear pot vs log on your 1M volume?

+1

[Papa Jim]

My bad. I had dug this amp out of the closet from where it had set for a long time and forgot I had already added a  MV years ago. You jogged my memory and all is good now. It sounds great. Getting some twang

thanks.