2 noob questions - What to do with center taps from PT & where do you wire NFB swithc

[jmardy]

Building a 5F2a from scratch.
Using an Allied 6K3VG
it has Red/Yellow and Green/Yellow center taps.

Weber layout shows these going to ground.
Is that right?
Grounded together to a chassis ground OK?

Also, all the cool kids have negative feedback switches in their tweed amps.
All I've found is that it removes the 22K resistor.
I need a picture, I'm that dense...

Thanks!

[Jazz P Bass]

That's all the feedback switch does.

Puts the 22K 'feedback resistor' In or Out.

[g1]

Yes, switch in series with feedback resistor. Open switch gives open loop, no feedback.
For PT center-taps, both go to chassis ground but make sure one side of heater winding is NOT grounded like original schematic shows, only center-tap gets grounded.

[jmardy]

Thanks.
Pretend I'm 12 though...
The switch either puts the 22K resistor between pin 8 of the preamp tube and the speaker output either in the circuit or bypasses it completely.
I.e. when the switch is open, there is no connection between pin 8 and the speaker jack.

Or am I even looking at the right 22K resistor?
???
(when I said noob...)

[g1]

We were simul-posting, see above.

[jmardy]

Yep.
Thanks.
Center tap, got it. Pin 9 not grounded so OK to ground center taps.
Re: 22K resistor
So I have it right?

Really appreciate the help and tolerance of such basic eye roll-ey questions.

[loudthud]

Building a 5F2a from scratch.
Using an Allied 6K3VG
it has Red/Yellow and Green/Yellow center taps.

Weber layout shows these going to ground.
Is that right?
Grounded together to a chassis ground OK?

Your question indicates that you do not possess the knowledge and experience necessary to safely build an amp from scratch. Serious injury or death could result. Do you have any electronic experience at all? Can you find a local mentor to help you?

[jmardy]

Your question indicates that you do not possess the knowledge and experience necessary to safely build an amp from scratch. Serious injury or death could result. Do you have any electronic experience at all? Can you find a local mentor to help you?

I know enough not to get shocked.
I've replaced caps and pots and know how to solder and build cables.
You guys are my mentors...
;-)

[g1]

The switch can go in series between the speaker jack and the 22K.
To nitpick about the terminology, it is not a bypass, but is breaking the NFB loop (To me, bypass would mean putting a short across the 22K resistor).

There is potential for complications, which are covered in this thread: http://music-electronics-forum.com/t10969/

[jmardy]

The switch can go in series between the speaker jack and the 22K.
To nitpick about the terminology, it is not a bypass, but is breaking the NFB loop (To me, bypass would mean putting a short across the 22K resistor).

There is potential for complications, which are covered in this thread: http://music-electronics-forum.com/t10969/

Thanks for the help!
I'd found that thread but wanted to double-check.

[jmardy]

So I've completed the build and learned a lot.
Some pictures in my other thread:
My first build has begun. - 5F2a from scratch

A lot of things made sense once I started the work.
Thanks all for the help and support.