06-29-2016, 05:07 PM
I have a Philco 640. A clear schematic can be downloaded here:
https://drive.google.com/file/d/0B-05OmK...sp=sharing
I bought it on Craigslist quite some time ago. The seller said it worked and I did power it up with a variac and was able to receive stations. Since then I shotgunned it and replaced ALL resistors and ALL capacitors. I did not touch any of the trimmers. I went to fire it back up last night and got nothing. No reception at all, regardless of band. The only thing I get is the normal slight power hum through the speaker when the volume is at maximum. I then tested all the tubes on both a Heathkit TC-2 and a Hickok 533 and got mixed results. I won’t post all the results but an example would be the second diode on the 85 tube testing bad on the TC-2 but testing good on the 533. Regardless, the radio did pick up stations prior to me working on it. I am not new to radio but and not a guru either. I shotgunned by father-in-laws Philco 42-1006, my TransOceanic B600 and, as shown in the next link, my Zenith 9-S-262:
http://www.antiqueradios.com/forums/viewtopic.php?f=6&t=197264
I checked all the voltages per the service information and here is what I got:
[Image: http://i12.photobucket.com/albums/a241/J...lgzk4d.jpg]
[Image: http://i12.photobucket.com/albums/a241/J...dmlte2.jpg]
I did nothing to the speaker other then test for continuity.
The one measurement I was not sure of was the screen grid on the 6A7 tube. The pin location in the service information did not have a location so I assumed it was the cap on top of the tube:
[Image: http://i12.photobucket.com/albums/a241/J...v9tfta.jpg]
When measuring there I got 0V. The pin cap was a little loose so I retested it on my TC-2 and it tested fine. I then stuck it back in and measured all the pin voltages:
[Image: http://i12.photobucket.com/albums/a241/J...ujgfku.jpg]
I tested the voltages on the 3 other tubes that have caps on top and got the following (cap to ground):
78 R.F. = -2.4V
78 I.F. = -0.5V
85 tube = -5.5V
Also, I measured the voltage in and out of the shadowmeter coil and got 270V and 260V, respectively. Ohms measurement was 1,551 ohms.
Any ideas on why I am not getting any reception?
https://drive.google.com/file/d/0B-05OmK...sp=sharing
I bought it on Craigslist quite some time ago. The seller said it worked and I did power it up with a variac and was able to receive stations. Since then I shotgunned it and replaced ALL resistors and ALL capacitors. I did not touch any of the trimmers. I went to fire it back up last night and got nothing. No reception at all, regardless of band. The only thing I get is the normal slight power hum through the speaker when the volume is at maximum. I then tested all the tubes on both a Heathkit TC-2 and a Hickok 533 and got mixed results. I won’t post all the results but an example would be the second diode on the 85 tube testing bad on the TC-2 but testing good on the 533. Regardless, the radio did pick up stations prior to me working on it. I am not new to radio but and not a guru either. I shotgunned by father-in-laws Philco 42-1006, my TransOceanic B600 and, as shown in the next link, my Zenith 9-S-262:
http://www.antiqueradios.com/forums/viewtopic.php?f=6&t=197264
I checked all the voltages per the service information and here is what I got:
[Image: http://i12.photobucket.com/albums/a241/J...lgzk4d.jpg]
[Image: http://i12.photobucket.com/albums/a241/J...dmlte2.jpg]
I did nothing to the speaker other then test for continuity.
The one measurement I was not sure of was the screen grid on the 6A7 tube. The pin location in the service information did not have a location so I assumed it was the cap on top of the tube:
[Image: http://i12.photobucket.com/albums/a241/J...v9tfta.jpg]
When measuring there I got 0V. The pin cap was a little loose so I retested it on my TC-2 and it tested fine. I then stuck it back in and measured all the pin voltages:
[Image: http://i12.photobucket.com/albums/a241/J...ujgfku.jpg]
I tested the voltages on the 3 other tubes that have caps on top and got the following (cap to ground):
78 R.F. = -2.4V
78 I.F. = -0.5V
85 tube = -5.5V
Also, I measured the voltage in and out of the shadowmeter coil and got 270V and 260V, respectively. Ohms measurement was 1,551 ohms.
Any ideas on why I am not getting any reception?
