Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: imgumby001 on December 02, 2020, 12:22:49 pm

Title: Artificial Center Tap Resistor Question
Post by: imgumby001 on December 02, 2020, 12:22:49 pm
I need to create an artificial 6.3 center tap on my current build and I don’t have any 1/2w 100ohm resistors, I’ve got a bunch of 1/4w. Is it dangerous to go that low? Will they just blow out?

Thx
Title: Re: Artificial Center Tap Resistor Question
Post by: pdf64 on December 02, 2020, 01:14:38 pm
The arithmetic is simple,
Power = voltage squared / resistance
So 6.3 x 6.3 =40
40 / 200 = 0.2W
That’s 0.1W per 100 ohm resistor.

Personally I used 5W, as in the case of s power tube fault shorting HT current to the heater circuit, I prefer them to hold and blow a fuse.
Title: Re: Artificial Center Tap Resistor Question
Post by: imgumby001 on December 02, 2020, 01:18:49 pm
The arithmetic is simple,
Power = voltage squared / resistance
So 6.3 x 6.3 =40
40 / 200 = 0.2W
That’s 0.1W per 100 ohm resistor.

Personally I used 5W, as in the case of s power tube fault shorting HT current to the heater circuit, I prefer them to hold and blow a fuse.

Thanks pdf. The math is what I need more than anything. Knowing where to apply it always alludes me. Looks like I’m taking a trip to radio shack!! Good thing we STILL have one out here in B.F.E.
Title: Re: Artificial Center Tap Resistor Question
Post by: Latole on December 02, 2020, 01:23:21 pm
Some amp use 47 ohms 1/2 watts , other use 200 ohms 1/2 watts.  You many choice.
http://www.valvewizard.co.uk/heater.html
Title: Re: Artificial Center Tap Resistor Question
Post by: imgumby001 on December 02, 2020, 02:38:51 pm
Some amp use 47 ohms 1/2 watts , other use 200 ohms 1/2 watts.  You many choice.
http://www.valvewizard.co.uk/heater.html

Thanks latole. I just went out and picked up some 100ohm 1/2 watters. It’s about 30min away, but it gave me the opportunity to upgrade my channel switch. I’m hemorrhaging money on this deal. Gotta love it!!