5F2-A w/ss rectifier prebuild help?

[ncusack]

Just wondering what everyone here thinks about the attached schematic for a 5f2-a build. Basically just wondering if the component values makes sense and if there is anything I should add or change.

Looking forward to all your suggestions.

[tubeswell]

yeah that oughta work okay
(Edit -Oops I didn't spot a couple of mistakes in the power supply)

[ThermionicScott]

Looks like you plan to use a bridge rectifier and still ground the CT of the power transformer -- is that correct? With that PT, I would expect a regular full-wave rectifier scheme.

- Scott

[MWJB]

What Scott says.

You have lower values for the power supply dropping resistors, your screen & preamp voltages wil then be higher than a real 5F2A.

Schem has the preamp coupling cap grounded to the same place as the main & screen supply caps - do not do this when you build. Ground preamp cap & preamp cathodes to input jack ground, the other filters ground to a PT bolt along with any PT centre taps & 6V6 cathode resistor & cap - separate wires for each component to ground point.

I wouldn't really bother with tieing the 2x100ohm resistors to the 6V6 cathode, it's debatable whether you will have enough voltage to adequately dc bias the heaters. If you advise as to B+ winding spec (VAC & current rating) I migt be able to adviseas to suggested values for a voltage divider from the B+ node to give you 35-40vdc on top of the heater VAC.

[ncusack]

Ok so heres the changed setup with full wave rec which i meant to do. and the grounds are labeled now i think. If you would change any values by all means suggest what you would do.

So is it better to just run the 100 ohm resistors off the heater direct to ground? I think i read somewhere that bruce from mission amps throws another resistor in series before those 100 ohmers hit ground.

http://img31.imageshack.us/img31/9919/princeton5f2a.png

[ThermionicScott]

Looks good to me. In my 5F2A build, I didn't notice a difference in hum between grounding the heater CT or attaching it to the 6V6 cathode, so I left it grounded.

- Scott

[Bruce / Mission Amps]

Ok so heres the changed setup with full wave rec which i meant to do. and the grounds are labeled now i think. If you would change any values by all means suggest what you would do.

So is it better to just run the 100 ohm resistors off the heater direct to ground? I think i read somewhere that bruce from mission amps throws another resistor in series before those 100 ohmers hit ground.

http://img31.imageshack.us/img31/9919/princeton5f2a.png

It won't work the way you have it drawn here...
The tone pot is wired wrong, well, it's not wired.
You have no grid load for V1b and the volume control will not work either unless it is grounded.
And yes, you will have enough voltage to bias the filament supply with the developed voltage across the cathode biasing resistor but it might not make a big enough difference to use it.

[ncusack]

Sorry meant to post this one. Thats what happens when i try and make forum posts when im leaving work and im late for a bus.

http://img685.imageshack.us/img685/6709/5f2ass.png

[ncusack]

Here is a rough layout for this build let me know if it matches your suggested grounding schemes. This build is going to be going into a 10x6x2 chassis so thats why it looks as cramped as it does

http://img191.imageshack.us/img191/7...2asslayout.png

[ncusack]

Please note there should be a wire from pin 7 of the 12ax7 to the volume pot

[MWJB]

"Please note there should be a wire from pin 7 of the 12ax7 to the volume pot" which will, of course, be shielded, shielding grounded at one end .

Why aren't you using grounded jacks? The jacks should be the ground points for input & speaker connections.

Mount your 1.5K grid stopper on the power tube socket (though, in reality you shouldn't need it if your layout is good)

You should not have all your filter caps daisy chained & all sharing the same ground point, preamp cap gets grounded to preamp ground. Componentscould have one ground wire each, all meeting at the prescribed ground point.

Your main && screen filter caps (and any other power amp grounds) should be grounded at the same place as the PT CT.

[ncusack]

Yeah shielded wire on input and from pin 7. The grid stoppers will be mounted on the tube socket thats why i had them floating off the board in that layout.

As for the power section being daisy chained is there a layout out there I could look at that has what your suggesting done to it?