01-03-2019, 10:34 PM
I've started in on the 38-116 that I picked up before Christmas.
Here's what it looked like to begin with:
[Image: https://farm5.staticflickr.com/4907/4635...0fba_z.jpg] [Image: https://farm5.staticflickr.com/4892/4459...fbbf_z.jpg]
Overall it's missing one acoustic clarifier but otherwise appears to be complete.
Also very little chassis rust (especially compared to the 37-690 I worked on this past Fall).
[Image: https://farm8.staticflickr.com/7891/4569...51d9_z.jpg]
As someone has helpfully noted on the tube layout label this is a Code 125 chassis with simplified RF subchassis - more on that in a bit.
That means Philco Service Bulletin 286A. And for those who like to follow along at home:
Speaker
The first thing I did was to measure the field coil and output transformer resistances - all look good.
Tubes
So there are 15 tubes on this set! That's another way of saying lots of points of failure I guess.
After testing them on the TV7/A:
* 6L6 GC - GE - 12/25
* 6L6 GB - GE - 37/25
* 5X4 G - NU - 56/40, 55/40, broken key
* 6J5 G - National Union - 54/50
* 6J5 G - Philco - 70/50
* 6J5 metal - Sylvania - 87/50
* 6J5 metal - Raytheon - 48/50
* 6A8 metal - RCA - 48/29
* 6A8 metal - Sylvania - 44/29
* 6K7 G - Sylvania - 26/36
* 6K7 metal - RCA - 64/36
* 6K7 GT - Raytheon - 54/36
* 6U7 G - NU - 35/40
* 6N7 G/GT - Philco - 54/38, 57/38
* 6R7 metal - Philco - dead
I ordered another 6L6GB with similar test results off of eBay right away. The others that were bad I can borrow from other sets until I find replacements.
Tube Shields
Right away you can see that there are a bunch of metal tubes. The 6L6 output tubes are a GE branded 6L6GB and 6L6GC.
These 1938 tube shield bases (unlike on the 1937 models I have) are clearly designed to prevent metal tubes from being used...which just means enterprising owners / repair men hacked up the tube shield bases to allow for metal tubes to be seated anyway. Nice one Philco.
[Image: https://farm5.staticflickr.com/4886/4568...401a_z.jpg]
[Image: https://farm5.staticflickr.com/4890/3255...684f_z.jpg]
[Image: https://farm8.staticflickr.com/7884/4656...c764_z.jpg]
After comparing my chassis with as many other 38-116 chassis as I could find on the Internet it's pretty clear that several of the tube shields on this one have either been...er..modified (read mangled). Or as in the case of the 6R7 and lower middle 6J5 tubes at the bottom left, removed entirely.
For reference, here's a photo of another 38-116 chassis (someone else's) with all of the tube bases intact (missing the 6R7 tube shield):
Anyway, there should be a total of 11 tube shields - on all but one 6J5, the 6L6 output tubes and of course 5X4 rectifier:
That last one really intrigues me. At first I thought that the one round aluminum tube shield had to be a non-original replacement. But in my search for chassis pictures I found the same round aluminum tube shield on most of them! Another clue: note that the tube shield base of the 6U7G (rearmost tube on the RF subchassis) is aluminum rather than plated tin like every other Philco tube shield on this chassis - or any other that I've seen. So I believe it's original (although was initially sitting on the wrong tube on mine). It's not called out in the parts list of the service bulletin. Perhaps someone here knows the answer to this riddle??
Here's what it looked like to begin with:
[Image: https://farm5.staticflickr.com/4907/4635...0fba_z.jpg] [Image: https://farm5.staticflickr.com/4892/4459...fbbf_z.jpg]
Overall it's missing one acoustic clarifier but otherwise appears to be complete.
Also very little chassis rust (especially compared to the 37-690 I worked on this past Fall).
[Image: https://farm8.staticflickr.com/7891/4569...51d9_z.jpg]
As someone has helpfully noted on the tube layout label this is a Code 125 chassis with simplified RF subchassis - more on that in a bit.
That means Philco Service Bulletin 286A. And for those who like to follow along at home:
Speaker
The first thing I did was to measure the field coil and output transformer resistances - all look good.
Tubes
So there are 15 tubes on this set! That's another way of saying lots of points of failure I guess.
After testing them on the TV7/A:
* 6L6 GC - GE - 12/25
* 6L6 GB - GE - 37/25
* 5X4 G - NU - 56/40, 55/40, broken key
* 6J5 G - National Union - 54/50
* 6J5 G - Philco - 70/50
* 6J5 metal - Sylvania - 87/50
* 6J5 metal - Raytheon - 48/50
* 6A8 metal - RCA - 48/29
* 6A8 metal - Sylvania - 44/29
* 6K7 G - Sylvania - 26/36
* 6K7 metal - RCA - 64/36
* 6K7 GT - Raytheon - 54/36
* 6U7 G - NU - 35/40
* 6N7 G/GT - Philco - 54/38, 57/38
* 6R7 metal - Philco - dead
I ordered another 6L6GB with similar test results off of eBay right away. The others that were bad I can borrow from other sets until I find replacements.
Tube Shields
Right away you can see that there are a bunch of metal tubes. The 6L6 output tubes are a GE branded 6L6GB and 6L6GC.
These 1938 tube shield bases (unlike on the 1937 models I have) are clearly designed to prevent metal tubes from being used...which just means enterprising owners / repair men hacked up the tube shield bases to allow for metal tubes to be seated anyway. Nice one Philco.
[Image: https://farm5.staticflickr.com/4886/4568...401a_z.jpg]
[Image: https://farm5.staticflickr.com/4890/3255...684f_z.jpg]
[Image: https://farm8.staticflickr.com/7884/4656...c764_z.jpg]
After comparing my chassis with as many other 38-116 chassis as I could find on the Internet it's pretty clear that several of the tube shields on this one have either been...er..modified (read mangled). Or as in the case of the 6R7 and lower middle 6J5 tubes at the bottom left, removed entirely.
For reference, here's a photo of another 38-116 chassis (someone else's) with all of the tube bases intact (missing the 6R7 tube shield):
Anyway, there should be a total of 11 tube shields - on all but one 6J5, the 6L6 output tubes and of course 5X4 rectifier:
- 9 square tube shields
- 1 large diameter round tube shield (on the 6N7)
- 1 aluminum tube shield (on the 6U7)
That last one really intrigues me. At first I thought that the one round aluminum tube shield had to be a non-original replacement. But in my search for chassis pictures I found the same round aluminum tube shield on most of them! Another clue: note that the tube shield base of the 6U7G (rearmost tube on the RF subchassis) is aluminum rather than plated tin like every other Philco tube shield on this chassis - or any other that I've seen. So I believe it's original (although was initially sitting on the wrong tube on mine). It's not called out in the parts list of the service bulletin. Perhaps someone here knows the answer to this riddle??
