In article ,
r (Mike Knudsen) writes:

The B- must be fed thru a filter choke, whose toehr end delivers it to
ground. The negative back bias developed across the choke is used to bias
the
audio output tube's grid negative. Its cathode is straight grounded, so if
you
run without this choke and B-, the output will draw excessive current and
distort.

That choke is in the same sealed case as the output transformer.

Exactly. The wires that come to the dynamotor include "B-" which is not
grounded. Hook it up as described and the choke will be in circuit.

A question for the poster I'm responding to: Is that 220 VDC max including
the choke, or just from B+ to chassis ground? I'm assuming the whole thing
(choke included).

It's what you see from B+ to B- at the output of the supply. There's a whole
description in the manual. The idea was to compensate for dynamotor output
variations.

73 de Jim, N2EY

"HeavyMetal" wrote in message
...
I acquired a BC-348 receiver. The receiver did play. But stopped. It
has a
110 volt mod.
I replaced the caps but the rectifier tube is shorted. The tube is a
Raytheon glass tube with shoulders. Ther is no tube mumber on it
except
'280' and 026' on thebottom next tot he name.
Anyone have an idea of what tube they used for the mod?
Thanks..



"280" is a manufacturer's code. In this case, it's Raytheon. Here's a
list of the codes:

http://www.triodeel.com/eiacode.htm

"026" is probably a date code. Maybe something like the 26th week of
1940 or 1950.

A four pin rectifier is almost certainly a 80.

Frank Dresser

In article , "HeavyMetal"
writes:

I replaced the caps but the rectifier tube is shorted. The tube is a
Raytheon glass tube with shoulders. Ther is no tube mumber on it except
'280' and 026' on thebottom next to the name.
Anyone have an idea of what tube they used for the mod?

That's a Type 80 tube. Go on rec.antiques.radio+phono and you will find
zillions of them, cheap. Or rewire an octal socket and use a 5Y3.

Check those pseudo-mica bypaass caps (pink) mounted along the side of the
chassis. They like to blow out, and take the screen resistor along for the
ride.
--Mike K.


Oscar loves trash, but hates Spam! Delete him to reply to me.

Thanks to all for the comments and suggestions.
It's a great ol' receiver. I really like it.
I'll keep everyone posted on the progress.....


"Mike Knudsen" wrote in message
...
In article , "HeavyMetal"

writes:

I replaced the caps but the rectifier tube is shorted. The tube is a
Raytheon glass tube with shoulders. Ther is no tube mumber on it except
'280' and 026' on thebottom next to the name.
Anyone have an idea of what tube they used for the mod?

That's a Type 80 tube. Go on rec.antiques.radio+phono and you will find
zillions of them, cheap. Or rewire an octal socket and use a 5Y3.

Check those pseudo-mica bypaass caps (pink) mounted along the side of the
chassis. They like to blow out, and take the screen resistor along for
the
ride.
--Mike K.


Oscar loves trash, but hates Spam! Delete him to reply to me.

"HeavyMetal" wrote in message
...
Thanks to all for the comments and suggestions.
It's a great ol' receiver. I really like it.
I'll keep everyone posted on the progress.....

Most often, what appears to be a shorted rectifier tube... It glows and the
plates turn red.... is not the tube itself, but a shorted capacitor
somewhere in the B+ wiring. There will be no charge for this diagnosis.
Old Chief Lynn W7LTQ since 1948 (first real receiver BC-348Q)

Lynn Coffelt wrote:
"HeavyMetal" wrote in message
...

Thanks to all for the comments and suggestions.
It's a great ol' receiver. I really like it.
I'll keep everyone posted on the progress.....


Most often, what appears to be a shorted rectifier tube... It glows and the
plates turn red.... is not the tube itself, but a shorted capacitor
somewhere in the B+ wiring. There will be no charge for this diagnosis.
Old Chief Lynn W7LTQ since 1948 (first real receiver BC-348Q)




RADIO 101....question all paper or electrolytic caps in a sixty year old
radio. "works fine, but..." is always the wrong answer.

-BM

The electrolytics was changed out as well as some paper caps.
One of the wires in the tube is broken and banging about..I think it shorted
and the trouble. Will keep posted..Thanks..Josh
"-Bill-" exray@coquidotnet wrote in message
...
Lynn Coffelt wrote:
"HeavyMetal" wrote in message
...

Thanks to all for the comments and suggestions.
It's a great ol' receiver. I really like it.
I'll keep everyone posted on the progress.....


Most often, what appears to be a shorted rectifier tube... It glows and
the
plates turn red.... is not the tube itself, but a shorted capacitor
somewhere in the B+ wiring. There will be no charge for this diagnosis.
Old Chief Lynn W7LTQ since 1948 (first real receiver BC-348Q)




RADIO 101....question all paper or electrolytic caps in a sixty year old
radio. "works fine, but..." is always the wrong answer.

-BM