7V on heaters of a EF86

[mat]

Is it too much ? Does it wear the tube down quicker than 6.3V ?

[ChrisM]

Is it too much ?

Yes

Does it wear the tube down quicker than 6.3V ?

Yes

[mat]

Ok, thanks for a quick answer I'll insert a 4,7 ohms 1/2 watt resistor in series with one of the filament pins right at the socket.

Is it too much ?

Yes

Does it wear the tube down quicker than 6.3V ?

Yes

[Phil_S]

Ok, thanks for a quick answer I'll insert a 4,7 ohms 1/2 watt resistor in series with one of the filament pins right at the socket.

I think that is the wrong strategy. If you have 7.0 on one tube, you should have it on all the tubes. Figure the current load (amps) for all the tubes and select a resistor that will do the job for all of them. Place the resistor between the transformer and the first tube.

If you don't know how to figure, post the tube lineup. Someone will help.

[mat]

It's the only tube. I built a pedal with one ef86 in it.

Ok, thanks for a quick answer I'll insert a 4,7 ohms 1/2 watt resistor in series with one of the filament pins right at the socket.

I think that is the wrong strategy. If you have 7.0 on one tube, you should have it on all the tubes. Figure the current load (amps) for all the tubes and select a resistor that will do the job for all of them. Place the resistor between the transformer and the first tube.

If you don't know how to figure, post the tube lineup. Someone will help.

[Firestorm]

Back-to-back diodes eat up the extra volts pretty easily. You lose the diode drop. Just have to be rated for the power (which sounds small in your situation.)

[mat]

Thanks for the tip. I'll try first with the 3W 4R7 I have.
Few pics of the (second) build http://www.flickr.com/photos/fuzzface19 ... 114234737/
Soundsample of the first version: http://soundcloud.com/mattit-1/diy-ef86od-pedal

Back-to-back diodes eat up the extra volts pretty easily. You lose the diode drop. Just have to be rated for the power (which sounds small in your situation.)

[Structo]

Sounds good Mat.

[vibratoking]

Some feel that a resistor in both sides of the heater circuit keep it more balanced in terms of noise. YMMV

[mat]

Sounds good Mat.

Thanks Tom

[mat]

Some feel that a resistor in both sides of the heater circuit keep it more balanced in terms of noise. YMMV

Ok, I'll try resistor on both sides if the noise is problem.

[mat]

2 x 10R in parallel on the other heater wire and got 6.008V on the heater. No noise problem

Might change the resistors to single 4R7 when I actually have one

Thanks for the tips !