Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on March 05, 2011, 07:41:01 am

Title: 12v Heaters - 6V6's in series?
Post by: LooseChange on March 05, 2011, 07:41:01 am

I have a PT with a 12v heater. I can run two 6V6's in series and I'm okay, right??

I have the standard Fender style pilot light assembly with the 6v light bulb already installed. Can't find a 12v to drop in. What to do with 6v bulb to not blow it?

The 12volt secondary has no CT, do I still use the 100ohm resistors to ground or do I need to change the values?

Thanks!

Title: Re: 12v Heaters - 6V6's in series?
Post by: sluckey on March 05, 2011, 08:04:49 am

You're fine running two 6V6 filaments on 12v.

Use a GE-1891 bulb. It's rated for 14volts. Probably at any auto parts store. Radioshack has a GE-1815 that should work also. Or put a resistor in series with the GE-47 6v bulb.

The 100Ω resistors will be fine but use 1 watt. Or if you want to stay with 1/2 watt, use 2 x 200Ω.

Title: Re: 12v Heaters - 6V6's in series?
Post by: jeff on March 05, 2011, 08:06:18 am

 Add a 2W 40 ohm resistor in series with the lamp. A #47 lamp runs at 6V @.15mA so you need to drop 6V.
V=I/R    
V/I=R
6/.15=40

6V X .15mA= .9Watts
double it to be safe round up 2W

Title: Re: 12v Heaters - 6V6's in series?
Post by: jeff on March 05, 2011, 08:10:27 am

 Sluckey must have posted as I was typing. I like his idea better get a different bulb. But then you got to remember.

Title: Re: 12v Heaters - 6V6's in series?
Post by: HotBluePlates on March 05, 2011, 09:31:29 am

Buy some NOS 12V6's. AES has them for $8.50 each. The picture for this tube on their website looks it could be a 60's RCA (no obvious label, of course).

Title: Re: 12v Heaters - 6V6's in series?
Post by: PRR on March 05, 2011, 11:21:30 pm

> lamp runs at 6V @.15mA so you need to drop 6V.
> 6V X .15mA= .9Watts

You mean A, not mA.

I'd go 47 or 50 ohms. No need to run a pilot light at FULL voltage. Dimmer lasts longer.