David Stinson wrote:


The big scare on Friday night was the unmistakable smell
of roasted resistor coming from the BC-348-R,
which then crashed, stone dead.
I brought plenty of spares parts and started
"resuscitation" right away. This receiver had been running
flawlessly for a month (as had the transmitter), but now
*three* paper bypass caps failed, leaking to short.
This toasted two dropping resistors, failing them *low-Z*.
One 4.7 K-ohm was down to 200 ohms. The real scare was
that these were in the IF plate leads, right through
the hair-fine wire in the IF transformer windings.
The way the receiver suddenly died, I was sure one
of the IFs had gone open, but there must have been an
angel watching over us, because new caps and resistors
plus re-alignment brought it back from the dead.

On the antique radio forums we make a point of driving home "replace
those go***mn paper caps because they are never good". You've been
around, Dave, You should know better!
Since this post is only to the BA forum instead of cross-posting to
rar+p I can admit that the only old radio out of dozens that I have not
been compelled to wholesale recap has been an English Barker 88 which
used surplus (at the time) metal cased US war-surplus caps. They all,
100%, passed any test I could give them.
More often it makes sense to yank the old paper jobbies and place giant
Orange Globs (for the non-restuffers) ...or in your case, assume they
were ok with the resulting consequence.
FB on the expedition's results..

-Bill WX4A

Were you trying to run a net with a BC348 as your primary receiver??

The I.F. is as wide as a gorge! When the band is hot I could never use 348
without the 'Q5er.'



"Bill M" wrote in message
...
David Stinson wrote:


The big scare on Friday night was the unmistakable smell
of roasted resistor coming from the BC-348-R,
which then crashed, stone dead.
I brought plenty of spares parts and started
"resuscitation" right away. This receiver had been running
flawlessly for a month (as had the transmitter), but now
*three* paper bypass caps failed, leaking to short.
This toasted two dropping resistors, failing them *low-Z*.
One 4.7 K-ohm was down to 200 ohms. The real scare was
that these were in the IF plate leads, right through
the hair-fine wire in the IF transformer windings.
The way the receiver suddenly died, I was sure one
of the IFs had gone open, but there must have been an
angel watching over us, because new caps and resistors
plus re-alignment brought it back from the dead.

On the antique radio forums we make a point of driving home "replace those
go***mn paper caps because they are never good". You've been around,
Dave, You should know better!
Since this post is only to the BA forum instead of cross-posting to rar+p
I can admit that the only old radio out of dozens that I have not been
compelled to wholesale recap has been an English Barker 88 which used
surplus (at the time) metal cased US war-surplus caps. They all, 100%,
passed any test I could give them.
More often it makes sense to yank the old paper jobbies and place giant
Orange Globs (for the non-restuffers) ...or in your case, assume they were
ok with the resulting consequence.
FB on the expedition's results..

-Bill WX4A

Albert & Btittany Spear wrote:

Were you trying to run a net with a BC348 as your primary receiver??

The I.F. is as wide as a gorge! When the band is hot I could never use 348
without the 'Q5er.'

I understand, but the whole point was to operate the special
event with as close to an actual, authentic 8th Airforce
WWII heavy bomber radio station as possible.
Otherwise, it would just be a contact with a typical 1950s ham rig.
So we announced on the net, on QRZ.COM, in QST
and on the DX reflectors, what we were doing and asked for help.
Most people did what they could to help-out and they were a godsend.
Even with QRM from the few bad apples,
I think we did pretty well.
73 Dave S.

"Albert & Btittany Spear" ) writes:
Were you trying to run a net with a BC348 as your primary receiver??

The I.F. is as wide as a gorge! When the band is hot I could never use 348
without the 'Q5er.'

BUt a wide receiver bandwidth means all the transmitters do not have
to be on exact frequency, something useful for net use.

And back when it was a current receiver, the BC348 would be extremely
useful for that. After all, transmitters were not frequency controlled
with the receivers.

Michael VE2BVW

Bill M wrote:

On the antique radio forums we make a point of driving home "replace
those go***mn paper caps because they are never good". You've been
around, Dave, You should know better!

I take your point, Bill, and I once agreed completely.
I've come around to a different attitude when it concerns
military radios with a historic angle. I now try to maintain
the original parts if I can satisfy myself that they are serviceable.
These guys were all tested and had been running without trouble for
some time. Of course, they are going to fail eventually.
I've just come to that point where "change as little as possible
and still bring it to life" has become my stand on these
rigs. I probably should have lowered the B+, as I've done
with other radios, which has helped preserve their original parts,
but I got cocky and overconfident on this one. It was
just pure luck and the grace of God that we didn't lose
an IF transformer. I could have replaced it, but it would
have meant working until dawn, instead of just until 1 AM ;-).

Thanks for the well-wishes. We're planning on doing another,
similar event in a year or so. The museum curator, Mr. Rigg,
was very enthusiastic about our efforts to preserve and
operate the equipment and says he's going to "draft" me to help
restore a B-24 they have. Yikes! ;-).
73 Dave S.