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Old September 25th 06, 06:24 PM posted to rec.radio.amateur.boatanchors
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Default Need help on Navy RCA RBB-5 RBC-5 Receivers

Hi, (2nd try to post, sorry if both show up)

I just purchased two receivers and the required power supply and connectors.
They a

Navy RBB-5, .50-4.0 MHz, built by RCA
Navy RBC-5, 4.0-27.0 MHz, built by RCA
Type 20130 Rectifier Power Unit, with 120V power cord, two receiver power cords
Two CN-49123-B 70 Ohm IMP. Antenna Cables with 4 plug panel

I have downloaded some partial manuals from the internet and am hopeful the
seller will find the original manual for me soon. The power unit can run two
receivers at the same time but manual indicates main usage is for one receiver
at a time. I have powered up both receivers using an autotransformer to
gradually get up to the 120V AC required for the power unit. Everything seemed
to power up fine and the receivers show 200V DC coming into them on their
voltage meter.

I am finding the following:

RBB-5 does not seem to receive anything from antenna, can hear steady static at
high volume.

RBC-5 picks up only very strong stations like Radio Havana.

Outside of chassis and shield of antenna cables on both receivers seems to have
about 60 volts AC on them.

I will be opening up the units soon to take a look. I have two tube testers and
a VTVM for testing.

I have a vertical HF antenna and a beam HF antenna that utilize standard 50 ohm
coax with PL-259 connectors. The 4 plug panel as I received it is set to
connect to a one-wire antenna and a ground wire (and also the cables running to
the up to four receivers).

I'd appreciate:

ideas on how best to connect my antenna coax to these receivers. The RBB-5

actually has two SO-239 connectors on the back but still doesn't pick up any
stations when connecting my coax directly to either SO-239.

ideas on what might be causing the receiver chasis's to be "hot"
ideas on what might be causing the lack of sensitivity (maybe my lack of

proper antenna connection?)
and knowing if anyone is enjoying using these receivers.


I'd like to use these receivers for both AM and CW.

Thanks,

Bill Bird
KG0YJ
Chesterfield, MO
www.billbird.com


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Old September 25th 06, 11:42 PM posted to rec.radio.amateur.boatanchors
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First recorded activity by RadioBanter: Aug 2006
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Default Need help on Navy RCA RBB-5 RBC-5 Receivers


ideas on what might be causing the receiver chasis's to be "hot"

=========================
The AC line input to the power supply has capacitors bypassing both
sides of the line to the chassis. That puts the chassis 60 VAC (one
half of the 120 VAC line voltage) above ground regardless which way it
is plugged in. Best idea is to install a 3-wire line cord and connect
the safety wire (the green one) to the chassis. You can also use a
polarized plug and bypass the neutral side of the line to the chassis
and the hot side of the line to the neutral. The 3-wire cord is the
best idea. --Ed

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Old September 26th 06, 04:03 PM posted to rec.radio.amateur.boatanchors
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Default Need help on Navy RCA RBB-5 RBC-5 Receivers

Bill Bird wrote:

RBC-5 picks up only very strong stations like Radio Havana.

Outside of chassis and shield of antenna cables on both receivers seems to have
about 60 volts AC on them.


You have very leaky capacitor issues. First of all you will probably find
an RF filter on the incoming power line made with a couple shunt caps.
If those caps are paper types, they are leaky and this is almost certainly
the source of the AC on the case. Replace those caps.

The poor RF performance and the leaky filter caps make me suspect that
you have a lot of other paper caps inside that have gone bad. Be VERY
careful of coupling caps used for DC blocking on the IF cans... replace
them immediately before they go bad and destroy an irreplaceable IF
transformer.

I will be opening up the units soon to take a look. I have two tube testers
and a VTVM for testing.


The tubes are almost certainly fine but it won't hurt to check them. You
will find a DVM is more convenient than a VTVM, but my basic feeling about
paper caps is that you're better off replacing them now rather than testing
them, replacing the bad ones now, and then having to replace the rest of
them later.

The orange drop types are reasonable replacements for a decent price,
but there are plenty of other good alternatives.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."


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