6.3v heater wire and jewel lamp time

[pjd3]

Hi there and once again, thanks for all your guidance through this.

Its time to begin wiring the "green" 18gauge solid wire. Although I'm pretty confident on how to go about it, it never hurts to hear your comments from experience, since it is my first tube amp build

As a general rule, I was going to keep the signal wires coming off the side of the tubes while keeping the heater wires more up and away, and coming down the middle of the tube socket, while keeping the heater wires as close together for as much as possible, until they needed to meet the tube socket lug. I've seen people do it the other way also, lifting the signals up and away and keeping the filament wires low. I just gathered there are different approaches for different people or layouts. I'ld love to hear some of your approaches and reasons for doing it that way, and also what you always try to avoid, trouble scenarios.

And since there is no 6.3V center tap, it looks like I'll be creating the faux center tap with the 2 100 ohm resisors to ground, probably from the lamp fixture
That brings me to the question, (actually 2 questions), Shall I best use a power ground for the 2 100 ohm resistors?
I have to wonder if I'm putting carts before horses here and should be more concerned about location or locations(s) for power ground.
Is it usually OK to say, use one or any of the PT mounting screws for termination power ground? I see different scenarios, of say, just one PT lug for all power ground terminations, up to using 2,3 or 4 PT lugs for power ground and have to wonder if one of those scenarios has benefits or drawbacks over the other. I"m not ready to hang my hat on any grounding scheme until I know a little more about the works on that.

Thanks for coming by. I value your efforts in my behalf!
{Phil - and as a reminder, this is Rob Robinettes BlackVibe 6L6GC layout and schematic almost exactly. The only thing I've really strayed from is the bias pot types.

[xtian]

Either approach to heater lead dress is valid. The more amps I've built, the less I worry about heaters injecting hum into my circuits. The ground scheme is paramount.

So, my preferred approach to grounding is that the HT CT (if there is one), the heater winding CT (which in your case is the two 100R resistors), the bias ground, the filter reservoir (first node) and the screen supply (second node) should all be grounded to a single point on the chassis, far away from the input jack. Everything else can be grounded to a buss wire, which in turn gets grounded to the chassis near the input jack.

[pompeiisneaks]

Yeah I agree with xtian on this, I just did a build with my heaters literally straight lines but they run away from the tubes and just dive in at the right spot to avoid being too close to the signal wires. It worked a treat.

~Phil

[pjd3]

Hey, thanks for all the guidance through this.

I realized I need to sort out the 6.3v heater config in my head better, before I accept my wiring as correct.
I'm using a Mojotone Bassman power transformer that illustrates a 6.3volt coil with no centertap, only a simple two conductor winding. I created the 2 100ohm faux centertap that I'm assuming goes to power ground. Is that correct?
So far I have the 2 indentical green wires from the PT going to the 2 lugs on the Jewel lamp fixure. Then, from the two 6.3volt lamp lugs to the filaments of the 2 6L6's.
When it was time to send the 2 heaters over to the 12AT7 and 12AX7, I began second guessing my understanding of how my configuration will be based on the available heater wires from the Mojotone Bassman PT.
Am I to send one of the green heater wires to both pin 4 & 5 and the other green heater wire to the common heater ground tube lug? Just when I think I've sorted this out, I get a brain fart about it again. Terrible. But, better safe than sorry I guess.

Thanks for your time. Dont' want to make any dumb mistakes.
Phil D.

[drew]

https://el34world.com/Hoffman/files/CommonHookups.pdf - see the diagram at the bottom of the page.

You can hang the artificial center tap resistors off the lamp lugs (if you don’t already have it set up that way).

[pjd3]

Hi and thanks Drew.

Yes, I did hang the faux 6.3v center tap off the jewel lamp fixture. What I would ask is if I ought to ground it to the chassis right there at the Jewel lamp vicinity or, combine it with all the other power grounds? (which I'm still mulling over the best location for the power ground.)

Thanks Drew,

Phil D

[Tony Bones]

I'm one of those people that is typically anal about grounds. But, I say ground the heater CT (real or faux) to the chassis anywhere you want.

[pjd3]

Thanks Tony, these are the things I try not to second guess on since it is my first tube amp build. I've successfully build many worthy audio devices but I hear alot about the neccessity of picky grounding on the tube amps. I appreciate the feedback for sure.

Thank you,

Phil D

[pompeiisneaks]

Although I did recently hear that you should really never ground the heater center tap, and always use a virtual center tap. If there's anything wrong with the heaters, the 100 ohm resistors burn up and you have a very cheap 'safety fuse' instead of burning up the transformer.

But I've been too lazy to go back to my last build and replace the heater center tap with them

~Phil

[pjd3]

Well Phil, that being the case, I guess my power transformer came with a built in "safety ground". Not having 6.3v center tap of its own, I was provoked to make my own with the 2 100 ohm resistors. And of course, being my first tube amp build I was completely neurotic about where to ground the home made center tap. The newbies like me must make many chuckle to themselves. I'm OK with that. No choice at this stage of the game1

Thanks Phil

[drew]

The Hoffman layouts that include the hookup for the artificial center tap at the far end of the board ground them to the main chassis ground point (typically one of the PT studs):

E.g., https://el34world.com/Hoffman/files/Hoffman_Plexi50.pdf

https://el34world.com/charts/grounds.htm