correct heater wiring

[gja]

Hi everyone,
I have a problem with a power supply.It´s a 260v dc + 6.3 (2x 3v +-) with a 5ar4 rectifer.one 16+16 cap.All my amps work well with another power supply,only difference being the heater which is 6.3 + ground.
When I use the 260v one the amps work but hum like hell.I´ve tried everything included creating a false center tap for the heater supply (100ohm resistors) and most of the other options.funny thing it works perfectly with a very basic 6sl7/6v6 se amp.but not with 832app,6v6pp etc (my other amps).
Any idea?I´ve searched the web and tried the options with no success.
Really stuck and desperate!
Thanks

[Soonerorlater]

6.3 (2x 3v +-)

..... is this ac?

only difference being the heater which is 6.3 + ground.

....is this dc?

brgds Bill


I have a power supplies transformer that provides 6.3v ac from two 3.15v ac secondary coils tied together in series. Where they are tied together forms a centre tap. Earthing this centre tap removes the hum, no false centre tap is required. If this doesn't work in your case then your search for the source of the hum might have to widen a bit

.

[DF96]

Does one amp assume a 'one side grounded' heater supply, while the other amp assumes a 'centre-grounded' heater supply? Either can be made to work, but the amp and the power supply need to agree on this.

[gja]

they all agree,no "one side grounded" heater supply,that´s why I am lost...
Wiring is clean,proper twisted wires close to the chasis etc...

[Soonerorlater]

Is the hum coming out of the speakers or is the transformer itself humming?

That 16 + 16 cap suggests it's old.

Perhaps it only has enough milliamps for a 6v6 se but not for 6v6pp and is complaining bitterly about the extra load.

What's the history of the transformer?

[azazello]

Of course PP amplifiers work without hmmmm, because current goes to every sholder of PP in different directions acros PP output transformer.
You can use in SE iron or transistor choke. Second variant is better, because
tr. choke cuts all riples. I can explain how to make it....I use always it in my SE amplifiers and hmmmm is zero!

[korey]

You need a power transformer with a seperate 5 volt tap to effectively run a 5AR4 tube. You need to isolate the 6.3 volt heater voltage from the high voltage.

Either that, or re-wire your rectifier circuit to be run with a 6CA4 rectifier tube where its filament is 6.3 volts just like the other tubes, and its high voltage is tapped off of the 6CA4's seperate cathode.

[gja]

Hi Korey,
Sorry forgot to tell the 5ar4 has it´s own 5v heater circuit.What do you mean by isolating the 6.3v from the high voltage?Caps?

[korey]

Not sure what it is that you are trying to do, but it sounds like you may need a seperate 6.3 volt transformer for the tube filaments, or isolate the grounded 6.3 volt chassis ground. Meaning, run the 6.3 volt wires to the filaments without it being grounded to the chassis in any way, shape or form.

[Soonerorlater]

Would like to know for sure that the power supply transformer is capable of driving the push-pull amps