[ARC5] Info sought about output transformer in BC-221-AK

[Leslie Smith]

  Hello James,

  Thanks for that info.  In this instance I'm not restoring or repairing
  a BC-221.  I bought a shabby set - no case, no calibration book,
  subbed tubes and with a crease in the side and front panel.   The
  (very naughty) fellow selling the "thing" told me "only the crease you
  see" and "didn't notice that" when I asked about the crease in the
  side panel.
So I'm using the chassis (and the output transformer) for another
purpose.I'm going to wring some useful performance from 3 tubes.  Sort of "well
built minimalist" approach.Also,  I cannot bear the thought of such a fine capacitor and tuning
gear going to scrap.That is the fate of gear that doesn't work.  (Sigh).  But in my workshop
it has found a home!
Thanks for your very useful info.

   73 de Les Smith
   vk2bcu at operamail.com

PS  I read the point about the low-Z phones and assumed they were 600
    ohms.That was my guess.  That would be a turns ratio of 3.65.
For 300 ohms = 5.1 :1 (or for 256 = 5.59)
I guess it's better to know than to guess.

   73 de Les Smith
   vk2bcu at operamail.com



On Sat, Jan 6, 2018, at 01:29, J Mcvey wrote:
> Just happened upon a passage in the manual that says 'later models
> used the HS-30 headset". I looked up the HS-30 and it's 256 ohms.> Like I said, they were in transition mode mode...
> 
> So, the primary should be about 8000 ohm s and the secondary should be
> 256 (300?) ohms.> If you find the turns ratio, it should fit this profile.
> 
> 
> On Friday, January 5, 2018 9:17 AM, J Mcvey via ARC5
> <arc5 at mailman.qth.net> wrote:> 
> 
> Leslie,
> 
> That was a very crytic entry! They will usually at least provide
> primary and secondary turns...> There may be a master "supply list" in that manual with more detail
> but I don't have time to hunt for it.> 
> None the less, it can be "reverse engineered" by looking uo the 6sj&
> tube data. At 100V is shows a class A plate resistance of 8250 ohms,
> so that would be the primary impedance. The secondary is probably
> called out in the Bc-221AK specs somewhere. Probably somewhere i the
> 600 to 3000 ohm area. They were in a headphone impedance transition
> back then, so different versions can require different headphones. If
> they don't call out the impedance , you may be able to find the spec
> for the supplied headset.> 
> Hope this helps...
> 
> 
> On Friday, January 5, 2018 5:16 AM, Leslie Smith
> <vk2bcu at operamail.com> wrote:> 
> 
> The subject line is the point of this posting.
> 
> More info:  (1) This transformer is shown as item 17 in the circuit
> diagram for the "AK".> The manual describes this as "output transformer".  
> I find no other information in the BC-221 manual.
> In particular I wish to know the impedance of the primary & secondary
> windings.> 
> Thanks to all,
> 
>   73 de Les Smith
>   vk2bcu at operamail.com
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net[1]
> Please help support this email list: http://www.qsl.net/donate.html
> 
> 
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net[2]
> Please help support this email list: http://www.qsl.net/donate.html
> 


Links:

  1. http://www.qsl.net/
  2. http://www.qsl.net/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20180106/e155ce44/attachment.html>