New 5e3p schematic with mods, I need someone to check my drawing!

[Crate50watt]

Hey team. Stumbled accross a 5e3p schematic and thought the cascaded channels sounded like a good idea.
I like the thought of having ss or tube rectification at the flip of a switch, coupling cap selector, and a 6l6/6v6 - 5y3/gz34 tube swappable option. I also added cathode or fixed bias for the power tubes and a tmb tone stack, with a push pull mid pot for a raw control. The first input I wanted to be voiced like a marshall, so that's the purpose of those components.

These are all the rob robinette mods in one amp. I could use a second, third maybe ten sets of eyes to check and make sure I didn't miss anything obvious or do anything really dumb. I attached a link to my FB page where you can see mine and the original schem in full res. I assume everyone knows the voltages and wattage of components.

https://www.facebook.com/rcampco/photos/a.254988608296584.1073741831.253171005145011/340090066453104/?type=3&theater

https://www.facebook.com/rcampco/photos/a.254988608296584.1073741831.253171005145011/340090083119769/?type=3&theater
Thanks in advance!

[sluckey]

Good luck! That's such a wild departure from a 5E3 circuit I don't know where to start. Show us a schematic, not a layout.

I'm pretty sure that ss/tube rectifier switch circuit will not work.

[Crate50watt]

Good luck! That's such a wild departure from a 5E3 circuit I don't know where to start. Show us a schematic, not a layout.

I'm pretty sure that ss/tube rectifier switch circuit will not work.

Hey sluckey, thanks for the input. I saw the ss/tube rectifier diodes were backwards and made the swap. In the process of drawing the schematic, I noticed numerous problems with my wiring diagram. I think at this point I've got it correct or close to where it needs to be. Hopefully the resolution is high enough. Let me know if anyone wants the full size schem sent to them.

Have a look and let me know if anyone sees any obvious errors! Thanks guys!

https://www.facebook.com/rcampco/photos/a.254988608296584.1073741831.253171005145011/344019956060115/?type=3&theater

[Crate50watt]

I just realized I have the MV in front of the third gain stage. Should that be after that, just before the phase inverter?

[DummyLoad]

bootstrapped concertina is drawn wrong. maybe the quirkiness of the as-drawn is what was desired, but i doubt that concertina works properly. attached is "fixed". also the 470k is not correct if it's a grid stopper to alleviate blocking distortion in the concertina, it needs to be inside the 1M bootstrap connected directly to the grid.


--pete

[Crate50watt]

bootstrapped concertina is drawn wrong. maybe the quirkiness of the as-drawn is what was desired, but i doubt that concertina works properly. attached is "fixed". also the 470k is not correct if it's a grid stopper to alleviate blocking distortion in the concertina, it needs to be inside the 1M bootstrap connected directly to the grid.


--pete

Hey Pete, I saw what you did there. Thanks for making that fix. That schematic was about the sixth version of it I had to draw because I kept finding problems.
And you are right, the quirkiness was not intended. It is just an indicator of my newbness.
And I think  I see what you mean about that 470k resistor needing to be moved.

https://robrobinette.com/5e3_Modifications.htm#Phase_Inverter_Grid_Stopper_Resistor

This is the mod I was copying, but upon further review it appears you are correct and I need to remove it. Also I think that I need to move the MV to behind the third gain stage, in front of the PI, behind that .022 cap.
Thanks again!

[Crate50watt]

Ok, I think I have it repaired, again. This is the sixth or seventh version of this haha. MV has been moved to behind the third gain stage. 470k grid stopper has been removed, in lieu of the new MV location. Bootstrap has been repaired, I think.

[JB]

I think I would put that coupling cap selector on the tone stack side of the caps, to avoid having 150-200V on the switch/front panel. Might also be less likely to pop.

You've got a superfluous set of 4007 diodes.  Your safety diodes pre the GZ34 are already rectifying the AC.  Another pair in series aren't going to add anything, apart from a diode volt drop.

[Crate50watt]

I think I would put that coupling cap selector on the tone stack side of the caps, to avoid having 150-200V on the switch/front panel. Might also be less likely to pop.

You've got a superfluous set of 4007 diodes.  Your safety diodes pre the GZ34 are already rectifying the AC.  Another pair in series aren't going to add anything, apart from a diode volt drop.

Good call on that selector switch, I will move that. Also, that second set of diodes is for solid state rectification. With the switch off or open it uses the tube, with the switch closed that second set acts as the rectifier. So, at the flip of that switch you can change from ss to tube rectified. Here is a link to the mod  :

https://robrobinette.com/5e3_Modifications.htm#Rectifier_Switch

And thank you for the input!

[JB]

I get the tube/solid state switching idea.  I'm just saying that the safety pair of diodes are already rectifying the AC so why add another pair of diodes downstream? Just switch between the safety pair and the tube.  Same result, fewer components and wires.





 

[DummyLoad]

Ok, I think I have it repaired, again. This is the sixth or seventh version of this haha. MV has been moved to behind the third gain stage. 470k grid stopper has been removed, in lieu of the new MV location. Bootstrap has been repaired, I think.

your MV is going to upset the bias of that cathodyne. please see attached.


--pete

[mresistor]

I don't think there is any harm using two diodes in series, they are cheap and so is wire, and two more would offer an additional level of safety if one burned up. I think I would use 1N5408 1000V 3A diodes but that's just me wanting to have something overspec'd. Look at the bassman bandmaster showman...

[mresistor]

Pete - would a Lar-Mar PPI Mv be a better option ?

[Willabe]

....just me wanting to have something overspec'd. Look at the bassman bandmaster showman...

When Fender 1st stated using SS diodes they were only good for something 400v or so. So Leo strung 3 in a line to get the voltage rating up to where he needed it.

Now a days with very reliable 1Kv SS diodes available we often only need 2 and sometimes 1 would be plenty.

A 3a diode is way over kill, most tube amps we work with/build are at most ~500mA in B+ current. So a 1A diode is over spec in almost all cases already. And the leads on a 3A diode are hard work/bend and hard to get in a standard eyelet.

We're much more concerned about the voltage rating than the current rating for what we need.     

[DummyLoad]

Pete - would a Lar-Mar PPI Mv be a better option ?

more complex for sure and not necessarily better. if you're not using NFB, then the MV in my last attachment works fine. if you plan on adding NFB, then you may want to consider the LAR-MAR.

--pete

[Crate50watt]

Ok, I think I have it repaired, again. This is the sixth or seventh version of this haha. MV has been moved to behind the third gain stage. 470k grid stopper has been removed, in lieu of the new MV location. Bootstrap has been repaired, I think.

your MV is going to upset the bias of that cathodyne. please see attached.


--pete

Beautiful. You guys are the shit! Thanks again!

https://www.facebook.com/rcampco/photos/a.254988608296584.1073741831.253171005145011/343659562762821/?type=3&theater

[Crate50watt]

Moved the coupling cap selector to the end of the tone stack. Adjusted some values I had off here and there. Here is an updated version.