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Couple things..
I powered the trans up on the bench and things look good with ~115vac in I got ~700vac on the two 80 plate (yellow) leads, and half that on each leg to the center tap (green). I got about 6.5vac on the filamet legs (black), and 5.09vac on the 80 filament legs (blue). No humming and it didnt get hot or even warm for that matter.
Second I have a question I had an issue getting all the wires back through the two holes on the bottom bell of the trans. A couple wires got mashed and I ended up having to take them back down fix the heatshrink since it solder joint pushed through. I'm thinking of opening up the holes a little or even cutting the metal between the two holes out to give more room.
Any thoughs on this?
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If you need to open the holes in the bell, no harm done. Put a proper fuse in place as well.
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State, Province, Country: Ohio
I found an error on the schematic I got for the 39-55. The detector/osciliator tube is labeled wrong. It lists the tube as a 6J8G when it should be a 6A8G. The tube image is correct just the label is wrong. The chassis layout shows the correct label for the tube. I found this when I was labeling the tube pins on the schematic I looked up the 6J8G and it was totally different then what was on the schematic.
Image from the schematic:
[Image: http://i1129.photobucket.com/albums/m501...-Wrong.jpg]
The 6J8G image (completely different):
[Image: http://i1129.photobucket.com/albums/m501...55/6J8.jpg]
(This post was last modified: 03-06-2012, 07:15 PM by ipwizard.)
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(03-06-2012, 06:37 PM)ipwizard Wrote: The re-wire is progressing.
[Image: http://i1129.photobucket.com/albums/m501...585e50.jpg]
[Image: http://i1129.photobucket.com/albums/m501...e65d68.jpg]
[Image: http://i1129.photobucket.com/albums/m501...ca1111.jpg]
[Image: http://i1129.photobucket.com/albums/m501...1c0615.jpg]
I did end up enlarging the holes in the bell of the transformer to get all the wires to come though with out snagging or getting crushed
[Image: http://i1129.photobucket.com/albums/m501...d871f5.jpg]
[Image: http://i1129.photobucket.com/albums/m501...4d67b7.jpg]
[Image: http://i1129.photobucket.com/albums/m501...71b31c.jpg]
[Image: http://i1129.photobucket.com/albums/m501...ac320e.jpg]
[Image: http://i1129.photobucket.com/albums/m501...856034.jpg]
Just to be safe I would install some rubber grommets in those holes, or at least wrap the bundle of wires with several turns of electrical tape. It doesn't take much for that sharp edge to rub through one of them when you least expect it and cause a light show.
Regards
Arran
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Agree you can split open a grommet, jam it in, and put a dot of glue to keep it in place if you forgot. Here's to a happy ending.
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(03-06-2012, 07:04 PM)ipwizard Wrote: I found an error on the schematic I got for the 39-55. The detector/osciliator tube is labeled wrong. It lists the tube as a 6J8G when it should be a 6A8G. The tube image is correct just the label is wrong. The chassis layout shows the correct label for the tube. I found this when I was labeling the tube pins on the schematic I looked up the 6J8G and it was totally different then what was on the schematic.
Image from the schematic:
[Image: http://i1129.photobucket.com/albums/m501...-Wrong.jpg]
The 6J8G image (completely different):
[Image: http://i1129.photobucket.com/albums/m501...55/6J8.jpg]
EDIT:
I think I am wrong about the 6J8G tube. The set I'm working on has a 6J8G tube. I just don't understand why the tube layout is so different looking (see pics above)! They must be using only part of the tube? Dosen't make sence to me.
The tube connections are correct if I go by the 6A8G tube.
Can someone help me out on this please?
(This post was last modified: 03-06-2012, 11:29 PM by ipwizard.)
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I think they made a mistake on the schematic. The tube placement diagram shows a 6A8G.
P.S. You can edit the pictures out when you post a reply. Just look for the [img]...[/img] stuff and delete it. It helps cut down on the photo overload 
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(03-07-2012, 12:03 AM)bandersen Wrote: I think they made a mistake on the schematic. The tube placement diagram shows a 6A8G.
P.S. You can edit the pictures out when you post a reply. Just look for the [img]...[/img] stuff and delete it. It helps cut down on the photo overload
True didn't think of stripping the images out on my last post.. Wifey was calling me to dinner and i was frustrated with this tube thing...
That must be what happened with the schematic they put the wrong tube diagram in. Maybe they left it in from the 39-116 schematic and it never got changed?
(This post was last modified: 03-07-2012, 12:22 AM by ipwizard.)
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Anyone have any tips of rebuilding a 4 pin speaker plug? I assume drill out the rivet and it comes apart but what to use to put it back together?
[Image: http://i1129.photobucket.com/albums/m501...042816.jpg]
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(03-06-2012, 11:27 PM)ipwizard Wrote: (03-06-2012, 07:04 PM)ipwizard Wrote: I found an error on the schematic I got for the 39-55. The detector/osciliator tube is labeled wrong. It lists the tube as a 6J8G when it should be a 6A8G. The tube image is correct just the label is wrong. The chassis layout shows the correct label for the tube. I found this when I was labeling the tube pins on the schematic I looked up the 6J8G and it was totally different then what was on the schematic.
Image from the schematic:
[Image: http://i1129.photobucket.com/albums/m501...-Wrong.jpg]
The 6J8G image (completely different):
[Image: http://i1129.photobucket.com/albums/m501...55/6J8.jpg]
EDIT:
I think I am wrong about the 6J8G tube. The set I'm working on has a 6J8G tube. I just don't understand why the tube layout is so different looking (see pics above)! They must be using only part of the tube? Dosen't make sence to me.
The tube connections are correct if I go by the 6A8G tube.
Can someone help me out on this please?
Normally when they use a 6J8 or a 6K8 the triode is used as the oscillator and the heptode section is used as the mixer, not sure what they did in this case. What chassis code does this set have 121, 122, etc?
Regards
Arran
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(03-10-2012, 11:59 AM)ipwizard Wrote: It's a code 121.
The schematic on nostalgia air also shows a 6J8 but the internals show a pentigrid convertor like a 6A8 not a triode-heptode. The schematic in my 1939 Philco book also shows it marked as a 6J8 but shows a pentigrid convertor like a 6A8. The 39-116 definately uses a 6A8 but since the 39-55 is basically a budget minded mystery control set with only the broadcast band I don't know why they would use a different tube. The only other Philco models that show a 6J8 in the tube complement are in the Tropic series, and those show a triode and a heptode section in the tube.
Regards
Arran
(This post was last modified: 03-10-2012, 09:18 PM by Arran.)
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Yeah its strange. I guess ill just have to deal with it. Hopfully things will just work. It might get interesting if I have to trouble shoot that section.
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Hmmm. All this talk of 6A8 vs. 6J8 tubes has me curious. I have a 39-55 out in the garage; I picked it up really cheap to have an extra stepper unit in case I find the one in my 41-616 is bad once I get started restoring it. I'll have to see what kind of det-osc tube it has in it.
Overly simplified comparison of the 6A8 and 6J8:
The 6A8 does not have a separate oscillator section, but the first two grids in the 6A8 perform the same function as the grid and plate of the triode section of the 6J8. In the 6A8, G1 is the oscillator grid and G2 is the oscillator "plate." The local oscillator signal produced here is mixed with the incoming RF signal from G4 to produce a third signal, or intermediate frequency.
In the 6J8, the (separate) oscillator grid G1 is connected to G3 of the heptode (mixer) section in order to inject the local oscillator signal; this is mixed with the incoming RF from G1 of the heptode section to produce the IF frequency.
In the 6A8, G3 and G5 are dual screen grids; in the heptode section of the 6J8, G2 and G4 are the screens. The heptode section of the 6J8 has an additional suppressor grid (G5), tied to the common cathode.
Compare both and you will see they have essentially the same pinout. Pins 2 and 7 - filament; 3 - plate; 4 - screen; 5 - oscillator grid; 6 - oscillator plate; 8 - cathode.
Can they substitute for one another? The tube substitution guides say "yes." While they might pass in an AM-only set, if the set has SW you should stick with the tube the set was designed for. Some even advocate using a 6K8 (a triode-hexode converter similar to the 6J8 but without the suppressor grid) in place of the 6J8.
Remember, any substitutions will affect alignment.
--
Ron Ramirez
Ferdinand IN
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