[ARC5] [Milsurplus] BC-221AK Question

[Mark K3MSB]

I have an LM-18.  It was gifted to me by a fellow that had used it for
years then switched to a more modern frequency standard.

[image: image.png]

73 Mark K3MSB

On Tue, Sep 2, 2025 at 1:41 PM howard holden <holden7471 at msn.com> wrote:

> *I have both the LM-18, which I just use with a makeshift supply, and a
> BC-221 (not sure which series, but it has 110V supply in it). Don't know
> which I prefer, perhaps the LM, they're both running fine. I use it with my
> GO-9 occasionally if I want to set it to an exact freq. Nice meters. Just
> remember they were built in WW2 (80+ years old) so they're not going to be
> as stable as when they were new. *
>
> *73, Howie WB2AWQ*
> ------------------------------
> *From:* arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> on
> behalf of Mark K3MSB <mark.k3msb at gmail.com>
> *Sent:* Tuesday, September 2, 2025 8:47 AM
> *To:* Ken Gordon <kgordon2006 at frontier.com>
> *Cc:* ARC5 <arc5 at mailman.qth.net>; List Milsurplus <
> milsurplus at mailman.qth.net>
> *Subject:* Re: [ARC5] [Milsurplus] BC-221AK Question
>
> Over the weekend I rebuilt the power supply.   It's using the original
> chassis and it's not going to win any prizes,  but it's providing 150V
> regulated voltage and 6.3 VAC now.
>
> Added a new cord and fuse etc.   The internal wiring was horrid;  I'm
> surprised it didn't short the B+ at some point....    fixed that stuff.
>
> A winter project is going to be doing a complete rebuild of the PS on a
> new chassis.
>
> The audio choke in the picture I posted is obviously not 150H..... in fact
> at 1 Kc it measures 1H.
>
> I have a hanger queen BC-221M and I extracted the choke from it.    Its
> 250 H at 1 Kc and it will have to do,
>
> Of course, the form factor is different so I'm going to have to bolt it on.
>
> [image: image.png]
>
> 73 Mark K3MSB
>
>
>
>
>
>
>
> On Wed, Aug 27, 2025 at 8:34 PM Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
> Hi Ken
>
> >> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>
> Yes, my typos.   Too lazy to roll over to the bench and get my
> glasses........     :-)
>
> [image: image.png]
>
> .... and thus the motivation for my question....
>
> [image: image.png]
>
> [image: image.png]
>
> The internal HB Power Supply was a "Widow-Maker" Special......with leaky
> caps!!!
>
> I will rebuild the PS tomorrow and power it up (after dressing the
> connections associated with the replacement components.....and using the
> correct parallel capacitor.
>
> 73 Mark K3MSB
>
>
>
>
> On Wed, Aug 27, 2025 at 7:46 PM Kenneth G. Gordon <
> kgordon2006 at frontier.com> wrote:
>
> On 27 Aug 2025 at 18:56, Mark K3MSB wrote:
>
> > I have a BC-221 whose ID plate says  BC-221E.   It is not an E
> > variant.
> > From the tubes, front panel controls, and TM11-300,  I think it's the
> > AK variant.
>
> I have two -AKs here: unfortunately. in storage, not in the shack. :-(
>
> > Looking at the front panel,  what is supposed to be behind the two
> > antenna connectors?
>
> Well, only ONE is an antenna connector: the "other" one is a ground
> connector...or should be.
>
> > I tried discerning it from TM11-300.   I think it's supposed to be a
> > 150 H Choke (Part 24) in parallel
> > with a 0.01 uF cap (Part 0-2).
>
> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>
> >    Can anyone confirm?
>
> Well, a 150 H choke would be physically fairly large for a "small" choke.
> I would have to go to my storage building and open one of my -AKs up to
> check, and cannot do that just now.
>
> I hope Wayne can help. If all else fails, I'll make a run to my storage
> and take look as soon as I can.
>
> BTW, the -AK version is one of only two other versons which include AF
> modulation capability. None of the others have that. This makes the -AK a
> fully functioning signal generstor.
>
> Ken W7EKB
>
>
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