Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jojokeo on July 13, 2013, 01:18:01 pm

Title: EL34 choke requirement for screens
Post by: jojokeo on July 13, 2013, 01:18:01 pm

Can't seem to find this anywhere & I don't have an amp to measure at the moment!? So what is the minimum current requirement needed for running two EL34's screens??? The chokes being on schematics & seen on transformer supply places just suggest the common replacements but 250mA and even 90mA ones I've seen seem to be overkill. I realize the other pi & preamp tubes also need to be considered their requirements are also very small.

2nd question: What is the actual max screen current for a 50w amp using 2 x EL34 at full volume/power?

Thanks much!

Title: Re: EL34 choke requirement for screens
Post by: tubeswell on July 13, 2013, 04:30:13 pm

My money would be on a 90mA rating to be 'safe'. Probably 50mA could cut the mustard

Title: Re: EL34 choke requirement for screens
Post by: PRR on July 13, 2013, 07:43:56 pm

Bookmark this Horse's Mouth:

http://www.mif.pg.gda.pl/homepages/frank/vs.html (http://www.mif.pg.gda.pl/homepages/frank/vs.html)

EL34 data from Philips 1969 (first EL34 link), page 3, shows 36W-55W all taking "2*25mA" (50mA) at max roar. Add a handful of little bottles, 60mA-70mA.

250mA is surely overkill. If 90mA is a Standard Part, that may be your Best Buy.

Title: Re: EL34 choke requirement for screens
Post by: jojokeo on July 13, 2013, 08:08:28 pm

Thanks for the input!!! I have one 90mA/4Hy 110DCR left "in my inventory" I want to use but wanted to make sure there wasn't something I was missing before going forward. "An ounce of prevention..."