'47 Philco console/record player restoration

'47 Philco console/record player restoration

Post by Joseph Piaz » Fri, 06 Oct 1995 04:00:00



I'm restoring a '47 Philco radio/phono console. The field core magnet
speaker is missing. Replaced with a similar vintage perm mag speaker,
and tried to use a power ***in place of the field core. I got 120
cycle hum. I finally replaced the ***with a 500 ohm, 20 watt
resistor. Is this about right? It is after the 5AZ4 rectifier, and
before the screen grids of the 6K6 push-pull outputs. This set uses
Philco 8-pin Locktal tubes, some of which when tested, seem to be soft,
and emission is low. Are these harder to come by than regular octals?
The set is a 47-1227, AM and FM. The phono unit looks to be in good
shape, though untested. Anybody have any ideas for me on restoring this
grand old radio?

Joe Piazza, N2MSG

 
 
 

'47 Philco console/record player restoration

Post by Larry Dowel » Fri, 06 Oct 1995 04:00:00


1000 or 1200 ohms would be closer to the DC resistance of the speaker
field.  

Regards, Larry

 
 
 

'47 Philco console/record player restoration

Post by SCOTTPA » Sat, 07 Oct 1995 04:00:00


If you get hum with the filter choke, you may have one or more dead filter
capacitors.  

If the two output tubes (7C5, 6V6 maybe) aren't more or less matched
(within 20% or so) in emission and/or transconductance, the ripple
rejection of the output stage will be decreased, and this will increase
the  hum level.  

You should suspect all paper capacitors, and should certainly replace at
least the coupling caps to the output stage grids.  If one fo these is
leaky, it will unbalance the output stage as well as increasing the
current drain and thus increase the hum two ways at once.  

Scott Robinson
my other car is a Citroen, too...and then there are the funny old bikes.