[ARC5] [Milsurplus] BC-221AK Question

[Mark K3MSB]

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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