2A3 PSE Choke spec? - World-Designs-Forum

Dave the bass · #1 29th May 2010, 11:43 AM

Hello,

I've got a WAD 2A3 PSE Choke, though I haven't got a 2A3 PSE amp! The DCR is 166R but I don't know its current or inductance, Does anyone know the spec of the choke in question?

Many thanks in advance Poppits,

DTB

Richard · #2 29th May 2010, 08:39 PM

Hi Dave,
Circ is here, http://homepage.ntlworld.com/richard...WAD/2a3crt.pdf
says 10H 180mA but doesn't quite agree with itself as each 2a3 is shown drawing 50mA so that's 200mA and if DCR is 166 then that won't make for a drop of 45V shown but it's going to be around a 250mA rating. 10H as shown? Best to put a meter on it but it's for SE so perhaps around that.

Dave the bass · #3 29th May 2010, 09:08 PM

Thanks for the reply and cct Richard.

Yeah, working with that diagram, if the DCR of that choke is 166R, then with 45 volt drop across it there's about 271mA being pulled through that choke (I think). I've measured mine, it's deffo 166R.

I'm using it in a little SE project at the mo, just wondered what it's spec was :-)

It's in a LCLC PSU, the other choke is a ginormous 250mA 10H beasty. This ex-WAD tinker is physically about half the size!

Cheers again for the help.

DTB

Richard · #4 31st May 2010, 07:29 AM

Hi Dave,
The circuit shows the draw as 200mA for the 2a3s and another 10mA for the 6sn7s = 210mA. If the DCR is 166 then the drop won't be 45V so something's wrong there plus the choke is shown as 180mA which is also clearly wrong. It may be 10H though, so best to measure it, as bear in mind it is for use in LCL and your big one may be for choke input use or of a higher current rating.

pre65 · #5 31st May 2010, 10:55 AM

Hi Richard

Are you suggesting that a choke used for "choke input" is different to one used for "cap input" ?

I ask because I am just about to start rebuilding one of my power supplies with bigger mains transformers (250-0-250 instead of 195-0-195) as choke input.

Richard · #6 31st May 2010, 11:16 AM

Hi Philip,
Yes, here's a bit about it, http://www.aikenamps.com/Chokes.html

pre65 · #7 31st May 2010, 11:29 AM

Thanks Richard.

The first choke is being replaced by a higher current version, as I will be using a bleeder resistor of 10K (after the first choke) to help transformer regulation and keep it in choke input mode whatever the circumstances.

Richard · #8 1st June 2010, 08:19 AM

Hi Philip, Is the bleeder resistor just for the pre tube supply after the output stage? I think the benefit of choke input will be negated with a resistor between choke and output stage. These things go hand-in-hand to make a choke for choke-input a bigger beast than a smoothing-only choke.

pre65 · #9 1st June 2010, 05:58 PM

The PSU is for my 300b amp and also my PT15 amp.

I have finished the rebuild but the bleeder resistor has yet to be fitted. Is stops the PSU slipping out of choke input mode with the consequent rise in voltage.

pre65 · #10 9th June 2010, 11:20 PM

The PSU has been modified again. The two grey 10H chokes have been replaced by two e-chokes which were developed on the AT forum by Mike Holmes with help from Nick G. The first cap (between choke 1 and e-choke) has been upped to 80uf and a 22R resistor inserted to stop the e-choke oscillating.

The net result has been an improvement on both amps (300b and PT15).