BC-348 receiver help.
 

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..

By the way, the tube is a four pin..
Thanks..

"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..

HeavyMetal wrote:

By the way, the tube is a four pin..
Thanks..

"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..





Sounds like a type 80, a very common type in it's day. IIRC the 2 in the
280 designation indicates the manufacturer.

73, Roger


--
Remove tilde (~) in e-mail address to reply
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/

In article , "HeavyMetal"
writes:

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..

Sounds like an '80.

If you replace the four-pin socket with an octal, or make an adapter, you can
use the much more common 5Y3GT in place of the "280". They're electrically the
same, but 5Y3s are smaller and much less expensive.

TWO IMPORTANT CAUTIONS ON THE BC-348!!

1) The BC-348 uses a rather unique circuit in the last audio, which functions
as both an audio power amplifier and a shunt regulator. Under no circumstances
should the B+ exceed 220 volts! The ideal B+ supply is between 190 and 220
volts.

2) The BC-348 B- (negative high voltage) is *NOT* grounded! It must be kept
isolated from ground in the power supply, unless major modifications are done
to the receiver. The receiver will work, sort of, with B- grounded, but it is
not recommended.

Complete manuals for the various models of the BC-348 are available free for
the download on KG7BZ's excellent website.

73 de Jim, N2EY

Hi..
Thanks Roger..appreciate it..


"Roger D Johnson" wrote in message
...
HeavyMetal wrote:

By the way, the tube is a four pin..
Thanks..

"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..





Sounds like a type 80, a very common type in it's day. IIRC the 2 in the
280 designation indicates the manufacturer.

73, Roger


--
Remove tilde (~) in e-mail address to reply
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/

"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.

In article , (N2EY)
writes:

2) The BC-348 B- (negative high voltage) is *NOT* grounded! It must be kept
isolated from ground in the power supply, unless major modifications are done
to the receiver. The receiver will work, sort of, with B- grounded, but it is
not recommended.

Right. 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.

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). --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
...

By the way, the tube is a four pin..

The conversion manual (1948) that I have shows a 5Y3. RM~

"Rob Mills" wrote in message
news:eTxRb.470$Le3.182@okepread04...

"HeavyMetal" wrote in message
...

By the way, the tube is a four pin..

The conversion manual (1948) that I have shows a 5Y3. RM~

A 5Y3 is the modern electrical equivalent to an x80 tube, and
much cheaper. Change to an octal socket.

Pete

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

" Uncle Peter" wrote

A 5Y3 is the modern electrical equivalent to an x80 tube, and
much cheaper. Change to an octal socket.


***** Modern? Seventy years ago more like!!!!!!!!!!

Brian Goldsmith.

"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

On Tue, 27 Jan 2004 18:00:13 -0500, " Uncle Peter"
wrote:


"Rob Mills" wrote in message
news:eTxRb.470$Le3.182@okepread04...

"HeavyMetal" wrote in message
...

By the way, the tube is a four pin..

The conversion manual (1948) that I have shows a 5Y3. RM~

A 5Y3 is the modern electrical equivalent to an x80 tube, and
much cheaper. Change to an octal socket.

Pete

By the way, isn't 5Y3GT a 5-pin octal tube?

JM
----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/