What is this thing inside my radio?
 

I've posted a picture of the underside of my RCA 9X571. My questions is
about that big black tube running diagonally in the picture.

According to the schematics and the SAMS under-chassis view, this is labeled
as capacitor C11 (I think .02mfd, it's not in front of me right now) and
resistor R11, a 10meg 1/2 watt resistor. Upon close inspection but without
tearing any of the black plastic covering, it look like it is a red coil of
stiff wire, with the black plastic tube vacuum-formed around it. I'm
guessing this might be the resistor itself, some kind of wire-wound low
wattage resistor? Why would they have used that? And, it looks like the
capacitor is inside the tube! If that's the case, would there be a
technical reason to put the cap inside a wire-wound resistor? One end of
the resistor goes to chassis ground.

I haven't poked around and traced everything out yet or really examined the
circuit , but has anyone seen anything like this?

Jeff

What is this thing inside my radio?
 

Assuming the pot is the volume control, it might very well be a shield for
the audio signal.

What is this thing inside my radio?
 

Unrevealed Source wrote:
I've posted a picture of the underside of my RCA 9X571. My questions is
about that big black tube running diagonally in the picture.

According to the schematics and the SAMS under-chassis view, this is labeled
as capacitor C11 (I think .02mfd, it's not in front of me right now) and
resistor R11, a 10meg 1/2 watt resistor. Upon close inspection but without
tearing any of the black plastic covering, it look like it is a red coil of
stiff wire, with the black plastic tube vacuum-formed around it. I'm
guessing this might be the resistor itself, some kind of wire-wound low
wattage resistor? Why would they have used that? And, it looks like the
capacitor is inside the tube! If that's the case, would there be a
technical reason to put the cap inside a wire-wound resistor? One end of
the resistor goes to chassis ground.

I haven't poked around and traced everything out yet or really examined the
circuit , but has anyone seen anything like this?

Jeff



If this is an AA5, could be the 455KC series coil/cap to tie the common
to chassis. Ken

What is this thing inside my radio?
 

"Unrevealed Source" wrote in message
...
I've posted a picture of the underside of my RCA 9X571. My questions is
about that big black tube running diagonally in the picture.

According to the schematics and the SAMS under-chassis view, this is labeled
as capacitor C11 (I think .02mfd, it's not in front of me right now) and
resistor R11, a 10meg 1/2 watt resistor. Upon close inspection but without
tearing any of the black plastic covering, it look like it is a red coil of
stiff wire, with the black plastic tube vacuum-formed around it. I'm guessing
this might be the resistor itself, some kind of wire-wound low wattage
resistor? Why would they have used that? And, it looks like the capacitor
is inside the tube! If that's the case, would there be a technical reason
to put the cap inside a wire-wound resistor? One end of the resistor goes to
chassis ground.

I haven't poked around and traced everything out yet or really examined the
circuit , but has anyone seen anything like this?

Jeff



Jeff,
Looking at Beitman's schematic, I see that C13 (0.02 uFd) from the volume
control wiper to V3 grid is shielded. Looks like that might be what you're
looking at. The black plastic-covered tube around the capacitor is the shield.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

What is this thing inside my radio?
 

That's a good guess, but C13 is a different cap. That one is shielded by
the common foil shield with a separate wire coming from it to ground.

"DaveM" wrote in message
...

Jeff,
Looking at Beitman's schematic, I see that C13 (0.02 uFd) from the volume
control wiper to V3 grid is shielded. Looks like that might be what
you're looking at. The black plastic-covered tube around the capacitor is
the shield.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters
in the address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

What is this thing inside my radio?
 

Ah. You may have been onto something. It is indeed C13, in Beitman's. In
Sams it's C11. Somehow I assumed that they would use the same parts list.
Silly me.

"Unrevealed Source" wrote in message
...
That's a good guess, but C13 is a different cap. That one is shielded by
the common foil shield with a separate wire coming from it to ground.

"DaveM" wrote in message
...

Jeff,
Looking at Beitman's schematic, I see that C13 (0.02 uFd) from the volume
control wiper to V3 grid is shielded. Looks like that might be what
you're looking at. The black plastic-covered tube around the capacitor
is the shield.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters
in the address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

What is this thing inside my radio?
 

Beitman 1950, page 128 (you need djvu to read them)

http://www.schmarder.com/radios/beitmans/index.htm

Schematic shows it as a shield around the cap from volume to V3 grid.

These days we'd probably mount the cap somewhere and run a shielded
cable but in point-to-point the components themselves often double
duty as 'connecting wires' so they've constructed a shield around it.

Looks like a brute force, last minute fix for a poor chassis layout problem.
It looks like the point to point run is longer than just the capacitor leads
would allow.

Phil B

What is this thing inside my radio?
 

IMHO, the 'golden era' of efficient layout and optimal use of components
began in the '30s and had, more or less, ended by the late '40s early '50s.
That shield sleeve looks costly to make and install compared to not needing
it at all. I agree with Phil that it is likely a last minute 'fix' for a
problem that should have been found with the prototype. The bosses used to
tell us, when there was a last minute change [technical or marketing] "fix
it, but don't change anything".
It seems that there is another golden era with these new ultra compact
devices like iPods and cell phones where they cram RF, digital and AF
circuits onto tiny PCBs and run them off a common no voltage power supply
and get very good performance.

Neil S.

"Phil B" wrote in message
news:D4Owj.9074$Sw6.1791@trnddc06...
Beitman 1950, page 128 (you need djvu to read them)

http://www.schmarder.com/radios/beitmans/index.htm

Schematic shows it as a shield around the cap from volume to V3 grid.

These days we'd probably mount the cap somewhere and run a shielded
cable but in point-to-point the components themselves often double
duty as 'connecting wires' so they've constructed a shield around it.

Looks like a brute force, last minute fix for a poor chassis layout
problem. It looks like the point to point run is longer than just the
capacitor leads would allow.

Phil B