Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: thelonious on July 05, 2012, 10:28:44 am

Title: Location/order of artificial heater center tap?
Post by: thelonious on July 05, 2012, 10:28:44 am

Working on converting an old 2x6V6 PA amp, and it has a bit of heater hum. It has no hum-balance pot or heater center tap. The heaters are wired in parallel.

When I add an artificial center tap, does it matter where the 100R resistors get wired into the heater chain? For instance, could I kill two birds with one stone by soldering the 100R resistors onto a power tube socket from cathode to each heater pin on the same socket, or is this a Very Bad Idea? :icon_biggrin:

Thanks!

Title: Re: Location/order of artificial heater center tap?
Post by: sluckey on July 05, 2012, 10:37:43 am

Sounds good to me.

Title: Re: Location/order of artificial heater center tap?
Post by: thelonious on July 05, 2012, 10:39:10 am

Thanks, Sluckey!

Title: Re: Location/order of artificial heater center tap?
Post by: HotBluePlates on July 06, 2012, 05:43:24 pm

For others' reference:

I know you normally see those resistors on, say, the pilot light of a blackface amp.

I built a 5E3 once and forget to include them during the build. Once the amp was done and fired up, the only easily-available room was at the first preamp tube. I crimped one end of both 100Ω resistors in a ring terminal. I bolted that down with the screw/nut holding one side of the first preamp tube socket. Then I soldered the other end to each end of the filament string at that tube (pins 4/5 and 9).

Worked perfectly. No need to keep those resistors at the PT end of the chassis.

Title: Re: Location/order of artificial heater center tap?
Post by: John on July 06, 2012, 07:02:37 pm

Quote

Worked perfectly. No need to keep those resistors at the PT end of the chassis.

I had always wondered about that. Thanks!

Title: Re: Location/order of artificial heater center tap?
Post by: Davidg on July 08, 2012, 03:33:38 am

yea that shouldnt be a problem-I have an old taynor that has it located between the PI and power tubes.Worried me a bit at first cause it was the first one I had seen like that and the schem had it by the pilot light.Had atube short and those resistors burnt up just like they should -actually twice before I found the short :icon_biggrin:

Title: Re: Location/order of artificial heater center tap?
Post by: thelonious on July 08, 2012, 07:26:57 pm

Thanks, guys! Worked like a charm. :occasion14:

Title: Re: Location/order of artificial heater center tap?
Post by: LooseChange on July 09, 2012, 05:35:36 am

Quote from: thelonious on July 05, 2012, 10:28:44 am

When I add an artificial center tap, does it matter where the 100R resistors get wired into the heater chain? For instance, could I kill two birds with one stone by soldering the 100R resistors onto a power tube socket from cathode to each heater pin on the same socket, or is this a Very Bad Idea?

I like it.