[aa8rv]

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

[Ron Ramirez]

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

[james1095]

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.

[Radioroslyn]

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