[ARC5] BC-453 Question BC-454 Also

[Rich Post]

Hi Scott,

Your mileage will vary.  I recently brought a couple of these back to
life.  I had acquired an ARC-5/ R27 and a Navy ARA CCT-46104, roughly
equivalent to the R-24.  Both very unhacked.  The R-27 still had its
dynamotor.  I used a variable regulated B+ to power each with the 24 volts
of filament supplied by a separate transformer.   Gently raising the
voltage up by way of the variable supply, the R-27 powered up unmodified
right to 250 volts at a measured 48 mA.  Very little is to be gained from
these beyond about 130-150 volts DC.  I had to turn the volume down even
with a B+ voltage of only 150 VDC at a draw of 27 mA.   I decided to leave
the R-27 in its good working unrestored condition, operating it at that
reduced voltage.

The ARA, on the  other hand,  was already drawing 50 mA at only 50 volts.
I throttled the voltage back so that the set was only getting 25 mA. After
a few minutes, I was surprised to be able to crank the voltage up to 135 at
that 25 mA but the magic didn't last.  One of the potted cap sections
decided to become a 700 ohm resistor.   I replaced that cap section and
powered it again, measuring the voltage on each of the cap sections and
disconnecting all that saw more than 6 volts, replacing them with tiny new
caps using the original wires wherever possible, mounting the new pieces on
the unique little terminal  strips in the center so that the restoration
could be reversible if I decided to restuff the little pots in the future.
After the cap replacements, the ARA ran at the same 250 at about 48 mA or
my B+ preference of between 130-150 volts.  I tried several solutions for
the B+, ending up building a voltage multiplier off the 24 VAC filament
supply.

I have a couple of already hacked "Q-5'ers" that need to be revived.  Time
for some more experiments.

73 de Rich KB8TAD

On Thu, Apr 2, 2020 at 11:27 PM Whitebear1122 <whitebear1122 at comcast.net>
wrote:

> Today I brought in from the garage a BC-453 that has been sitting out
> there for several years. It has been sitting in an old timers basement
> since the early 60’s so it was gunky with grime.  So I had to clean it up
> before I wanted to get to close to it..  It cleaned up nicely with some
> GOJO and a tooth brush, and looks great.
>
> I’m thinking of building a Q5’er with it.
>
> Question for you experts:  How would you approach powering this up? One
> option is to just plug it into a variac and slowly bring it up and find out
> what happens.  Another approach would be to disconnect all the 0.05 or 0.5
> cans and measure capacitance and leakage current.  Another approach is to
> shot gun replace those caps.
>
> I know there has been a lot of discussion about recapping the BC-348
> Micamold caps and just getting it over with.   What about the ARC5
> receivers?  What has been your experience?
>
> Thanks, Scott WA9WFA
>
>
>
>
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