[ARC5] 2 RX in rack with p/s and FL-8 Filter being worked on

[Tom Bridgers]

Just purchased on Ebay,  2 ea BC-454 RXs in a 2-RX rack.  Both RXs and the 
rack are heavily modified, with a power supply mounted on a shelf of "L" 
shaped aluminum plate attached to the rack.  An FL-8 filter is permanently 
connected to the receivers on the back plane.

Judging from the amount of dust, mouse hair, assorted other stuff, and 
crumbling condition of the power cord, I'd say these receivers, rack, power 
supply and FL-8 were modified and assembled in the early 1950's ... then put 
away and stored in a barn or garage for some 30 or 40 years.  Everything is 
pretty dirty, grimey and greasy.

So far I've been able to figure out:
1.  Power supply is working and under load it puts out about 255 volts. 
After running the RXs for about 5 minutes the voltage drops to about 246 
volts.  There is an 800 ohm resistor (which gets very hot)  preceding the 
capacitor input filter section with the choke being at least a 100 ma 
Stancor model.
    The power supply simultaneously supplies B+ and filament voltage to both 
receivers.
2.  The original owner had removed all 4 of the dynamotor shock mounts on 
each receiver and used them as access holes to feed wiring into and out of 
the receivers and to make connections between the receivers, as well as to 
the rack, FL-8, and power supply.  The wiring is not neat and organized ... 
and in these situations, the term sphagetti comes to mind.
3.  Neither receiver receives signals.  But the audio sections are working 
and I get a nice volume of static.
    A. So far I've tested the current drawn of one receiver, and it is high. 
It's 55 MA, rather than the normal 30 MA.  No doubt some leaky caps need to 
be found and replaced.
    B. It appears that the BFO has been removed from one of the receivers. 
Which is a bummer.  Why would the original owner do that, I wonder?
    C.  On the first iteration, after about 5 minutes, I noticed a 12SR7 was 
cold to the touch.  So I replaced it, and fired it all up again.
4.  Headphones plugged into the A-Tel jack on the rack are switchable 
between the two receivers.  Never having used a rack before, I got very 
excited when I found out how the system of rack switches work.  In essence, 
in this configuration, this arrangement allows you to "guard" one frequency 
and then cruise around and listen to any other freq's covered by the other 
receiver.  Pretty neat.
5.  The FL-8 filter appears to be working, as I hear a difference in the 
static level when it is switched among voice, beacon , and both.

Next Steps:
o  Clean the RXs, rack, etc some more!
o  Disconnect the wires to/from the power supply, to each receiver and to 
the FL-8, so the RXs can be removed from the rack for troubleshooting. 
Label wires so I can reassemble the dang thing.
o  To lower the operating voltage a bit (say to 150 to 175 volts), replace 
the 800 ohm, 15 watt resistor  in the power supply with a  25 watt resistor 
of resistance to be determined.
o  Reverse engineer the wiring modifications so they can be documented.

That's it for today.

I'm thinking this lash-up of receivers paired with a T-19 or BC-696 TX would 
be a VERY nice 80 meter station.  And that is the direction in which I'm 
headed....
73's,
-Tom  KE4RHH