Philco 38-12 dial lamp and 6A7 Tube - Printable Version
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+--- Thread: Philco 38-12 dial lamp and 6A7 Tube (/showthread.php?tid=3919)
Philco 38-12 dial lamp and 6A7 Tube - aa8rv - 11-07-2011
Hi,
Restoring a Philco 38-12. If the 6A7 tube isn't functioning would that be a cause for the dial lamp not to turn on? I'm getting static but no reception of signal. I have replaced all caps. I noticed that the 78, 75, 41 and 84 tubes lightup, but the 6A7 does not and the grid cap is extremely loose. I tested the tubes on a Precision 612 tube tester and the 6A7 tested to replace. Voltage readings are as follows:
Tube 41:
S= 194vdc
G= -10vdc
P= 176vdc
Tube 84
K=249vdc
Tube 75
P=83vdc
D1= -2.4vdc
D2= -2.4vdc
K= -2vdc
Tube 78
P= 189vdc
S= 100vdc
Tube 6A7
Osc P=186vdc
Osc G= 0
S=99vdc
P=189vdc
+ side 12uf (I used 20uf) to - electrolytic = 254vdc
+ side of 4uf(I used 8uf) to chassis ground=196vdc
Voltage reading were taken with 113vac input
Thanks,
Mike
http://www.nostalgiaair.org/Resources/236/M0013236.htm
Re: Philco 38-12 dial lamp and 6A7 Tube - Ron Ramirez - 11-07-2011
aa8rv Wrote:If the 6A7 tube isn't functioning would that be a cause for the dial lamp not to turn on?No, but you had better check that dial lamp socket; it is probably in need of rebuilding. Details here:
http://www.philcoradio.com/tech/lamps.htm
Re: Philco 38-12 dial lamp and 6A7 Tube - james1095 - 11-13-2011
That set uses a parallel filament arrangement with a power transformer so there's no interaction between the dial lamp and the tubes like there is with a lot of the "AA5" series string sets. Have you checked for voltage at the socket and continuity of the bulb filament? I've seen bulbs that were open despite no visible break in the filament. There just aren't many things that can prevent the bulb from lighting if any of the tubes glow. I'd start by replacing the bad tube since it's obvious the set won't work with the bad one. That will probably get the radio working.
Re: Philco 38-12 dial lamp and 6A7 Tube - Radioroslyn - 11-14-2011
Pull out the 6A7. Take your ohm meter and hook it to the two fat pins of the 6A7. Should read a very low resistance like .5ohm. If not you will need to replace the 6A7, it's DEAD
Terry N3GTE