Question about Heather circuit configuration

[kagliostro]

Some time ago we discussed about this argument but I'm not able to remember the conclusions

Having a PT that has only a 6.5v-0-6.5v Heather winding

which is the best way to connect the final tubes (a pair of 6V6) ?

is better to connect the CT of the winding to ground and the Heather of the tubes simply in series

or is better co connect to ground also the junction of the two Heathers (having a sort of virtual CT) ?


Many Thanks

K

[stratele52]

6.5-0-6.5  ???? You are sure of that ? None of your sketch are go to me .

Use only one side 6.5 and 0 . Boths tubes in parralel ,like any standard heater wiring . Floating heater wire.

Don't put the 0 to ground . Use two 100 ohms resistors to ground to make an artificial center tap

[kagliostro]

The way you say 1/2 of the disposable current is lost

The transformer is from an Ibanez TSA15H

in that schematic Ibanez have the 6V6 tubes in series not connected at the junction to ground

but if you want to have all the disposable current you must use both windings and CT of the transformer

K

[stratele52]

Second sketch are better than the first one in you need full current.

[HotBluePlates]

is better to connect the CT ...

Both options are functionally the same.

If you connect the tube heaters in series and only connect the CT to ground, the junction of the tube heaters will float to approximately 0v. So it really doesn't matter if you make a wire connection from that point to ground, or if you connect only the CT to ground.

[kagliostro]

Many Thanks

K

[spacelabstudio]

They look functionally identical to me.  Possibly one would have a different hum rejection than the other, but then again, this is the power section.  My vote is probably doesn't make any difference.

[PRR]

There is a difference if one of the 6V6 tubes falls out. (Or the heater burns open.)

[kagliostro]

And which will be your choice PRR ?

K

[HotBluePlates]

There is a difference if one of the 6V6 tubes falls out. (Or the heater burns open.)

Well that's true...

In that case, if you had the junction of the 6V6 heaters grounded, the tube with the intact heater (or still in the socket) continue to function.

If you don't ground the junction of the 6V6 heaters, the remaining tube stops working because the circuit is opened (no path for heater current to go around the circuit). If the tubes are still in the sockets, that could be a good tip-off that the heater opened, which would be hard to suspect/troubleshoot otherwise. You'd check continuity of the tube from pin 2 to 7 to determine which tube has the open heater.

Maybe I've been lucky, but I've never encountered an open heater. I've seen tubes with almost no emission which still had an intact heater.