Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bartman on July 20, 2012, 04:20:08 pm

Title: Wire gauge question
Post by: bartman on July 20, 2012, 04:20:08 pm

In June I bought a MOD KIT 102 amp kit ( 1x12ax7, 1xEL84, SS rectifier). (I know, sorry now). Any way, every thing I'm seeing now uses 20ga wire for AC/DC signal/supply voltage but 18ga wire for the heaters. My kit supplies 20ga for all. 1amp slo-blow mains. Most Fenders use either a 2 or 3amp fuse. Is 18 gauge necessary for the heaters?

Thank you,
Bart

Title: Re: Wire gauge question
Post by: sluckey on July 20, 2012, 04:41:33 pm

Quote

Is 18 gauge necessary for the heaters?

Not for that amp.

Title: Re: Wire gauge question
Post by: bartman on July 20, 2012, 05:22:06 pm

Thank you Steve,

Is htr wire gauge based on pwr tubes (first in feeding chain)?

I have a '67 BF Bassman (AB165) I'd like to backdate. Should I use 18ga htr wire?

Thanks,
Bart

Title: Re: Wire gauge question
Post by: John on July 20, 2012, 08:43:16 pm

I think quite a few people use 18 gauge on the power tubes and 20 on the preamp tubes. Come to think of it, that's what I did too.  :icon_biggrin: HTH.

Title: Re: Wire gauge question
Post by: archaos on July 24, 2012, 07:13:56 am

Quote

Is htr wire gauge based on pwr tubes (first in feeding chain)?

I have a '67 BF Bassman (AB165) I'd like to backdate. Should I use 18ga htr wire?

Thanks,
Bart

The wire gauge is based on the current drawn by the tubes. In an AB165 there are :
2 x 6L6GCs requiring 0.9A each in the power section
3 x 7025 & 1 x 12AT7 requiring 0.3 each in the preamp section
Furthermore, we know that the load carrying capacities of 18GA wire & 20GA wire are respectively of 2.3A & 1.5A.
Therefore you need 18GA for the power tubes & 20GA for the preamp tubes to be safe.
Yet, you can a fortiori use 18GA everywhere to be safe as well.