[ARC5] BC-454 Conversion
Dennis Monticelli
dennis.monticelli at gmail.com
Sun Dec 23 20:44:59 EST 2007
The filaments add up to 25.2V but you can use 28V as another fellow
has noted. Even a high amperage 24V transformer will work as the
lighter load of the ARC-5 will yield >24V. Connectors for the rear
are uncommon (though they do exist) but you can use mini-banana plugs
in the socket holes. Likewise mini-banana jacks will fit the dyno
plugs where you bring in power. Be careful of the many bathtub caps
and B+ electrolytic having excessive leakage. You can minimize the
need to replace some of them by keeping the B+ well below the 250V the
dynos put out. Some folks run the B+ off the same 28V DC supply they
feed to the filaments and report acceptable performance. Audio output
will be low and overall receiver gain will be down. An external audio
amp is helpful when gain is that low. I have had better luck running
about 60V but did have to replace a few caps to reach that voltage.
The audio output Z is usually wired for several K ohm (4K or higher)
though some units (with a B suffix) had the output transformer wired
for 600 ohm. In any case, an external step down transformer is
called for if you want to drive a speaker. With about 60V B+, the
speaker can be driven adequately without the aid of an external amp.
If your B+ current while running 60V is more than about 10 to 15mA
then you probably have leaky caps. I suggest you slowly apply B+
while monitoring the supply current when powering it up for the first
time. You may get lucky and be able to ramp up to a sufficient
voltage without having to replace original caps.
Of course you will need to do the standard mods to add a gain pot and
BFO switch to the front panel. You can do this by modifying an extra
front drawer, or finding an existing modified drawer (they are common)
or you can make your own out of a piece of aluminum plate. There is
an uncommon ARC-5 accessory drawer than has all this built in....if
you can find one.
You don't have to be invasive in bringing the BC454 to life. Good luck
with your project.
Denny AE6C
On Dec 23, 2007 12:36 PM, Bob Macklin <macklinbob at msn.com> wrote:
> Aircraft actually had 28V systems.
>
> Bob Macklin
> K5MYJ
> Seattle, Wa,
> "Real Radios Glow in the Dark"
>
> ----- Original Message -----
> From: "Chuck Hurley" <scorebrd at verizon.net>
> To: <arc5 at mailman.qth.net>
> Sent: Sunday, December 23, 2007 11:25 AM
> Subject: [ARC5] BC-454 Conversion
>
>
> As a kid I had an Arc5 receiver that I used as a Novice. Recently I came
> across an unmolested BC-454. I am interested in converting it but at the
> same time not hacking it up.
> So I have a number of questions that perhaps can be answered before I
> proceed.
>
> 1. The original filament circuit was based upon 24 volts. I have access to
> a number of 28 volt
> transformers that would work fine but I would need to know what value
> of resistor to use to
> drop the value to 24 volts? This would keep the filament wiring
> intact.
>
> 2. I would like to make connections to/from the receiver through the
> existing connector.
> Are mounting plates/connectors available or scarce?
>
> 3. Does anyone have a dynamotor that is not working that I can use the
> shell and plug
> as a means of making power connections through the 3 prong connector?
>
> 4. How is speaker audio obtained? Does the output transformer have to be
> changed?
>
> Thanks for your help
> Chuck K1TLI
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