tube heater wiring question

mkruger · Jan 7, 2005

Never worked with tubes before so I want to double check how to wire the heater on a 12AU7 (ECC82) tube... I'll be using 12VDC. The tube has two hear pins, so do I just connect one pin to positive and the other to ground like a light bulb?n this case I assume polarity won't matter.

thank ye :guinness:

CJ · Jan 7, 2005

There are three heater pins, 4,5 and 9.

Hook one end to 4, and the other end to 5.
Leave 9 alone.
Polarity does not matter.

PRR · Jan 8, 2005

> like a light bulb?

Yes, but....

> the heater on a 12AU7 (ECC82) tube... The tube has two heater pins...

Uh, three, as CJ sez.

Internally, it is "two 6V light bulbs". So you can use it either at 6V or at 12V. The two "lamps" are wired to 3 pins. If you squint at the base diagram, you see how you can wire in parallel for 6V or series for 12V.

mkruger · Jan 10, 2005

I'm getting more confused, how would I wire in series for 12VDC on H1 and H2?

Would H1 be 12VDC with H2 connected to ground?

CJ · Jan 10, 2005

The 5687 has the same pinout as the EC.

4,5 to ground on the EC, 9 of the EC goes to 4 and 5 of the 5687, then 9 of the EC goes to plus 12 volts.

PRR · Jan 10, 2005

That drawing is "simplified", which is why you are confused. Get a proper pinout diagram. Put the tube number in Google, you usually find a data sheet quick.

12AU7

NOTE: three heater pins, 4, 5, 9

6V: tie 4+5 together, apply one end of 6V to 9, the other end of 6V to 4+5.

12V: ignore pin 9, put one end of 12V on pin 4, the other end of 12V to pin 5.

> Would H1 be 12VDC with H2 connected to ground?

In fact, yes. But "H1" "H2" are not standard names for these pins, only on that drawing you have. And marking pin 9 as "NC" is -dangerous-...: when a tube maker marks a pin NC that means you can use that socket lug for other purposes, a handy tie-point to support components. But 12AU7 pin 9 is not NC, it has heater power on it (even when only feeding pins 4 and 5).