AW-15 Oscillator Circuit Question

[Joseph W Strickland]

In the All-Wave 15 oscillator circuit there is one coil identified as part no. 135-30. In that coil assembly there is one capacitor that I believe is a 1200mmFd or 1700mmFd. The copy is so poor that I cannot make it out. Could someone who has one identify that capacitor for me?

Thanks in advance.

Joe

[David C. Poland]

Joe - What is your AW-15 documentation reference page or diagram?

If a diagram, what is the date of the diagram?

       4/10/34,  5/5/34, 11/19/34,  1/12/35    or

        undated (Summer 1934?) with a 55 tube 2nd detector, 55 diodes in push-pull off the last IF coil  ??? 

On a factory reference page, I see a coil wheel diagram both top and bottom views, and a parts list showing on blue band coil #120 having part # 135 as a 3000 MMFD cap.

This page also shows a bottom view of the Amp and parts list.

AND - are you really in need of messing with the parts on the coil wheel?

[Joseph W Strickland]

4/10/34 with Wunderlich tube. I have no set. I am working on cleaning up the schematic to produce a more legible one.

Joe

[David C. Poland]

Looks more like 1200 mmfd  -  but I am unsure. Not sure I will really be able to say.

[Joseph W Strickland]

David;

That is what I think too. 1200pF is a fairly common value. 1700pF, while possible is not nearly as common as 1200, 1500 and 1800pF values.

Another item has surfaced - there is a 1 F on the secondary of the 1st, 2nd and 3rd IF transformers. It is not reasonable that it represents a 1 Farad capacitor, so what does it represent? Possibly IF instead? It also appears that there is a capacitor at about the center of the IF secondary winding between the primary and the secondary winding. At first I thought it was just a blurred dot indicating a connection but closer inspection looks more like a primary to secondary coupling capacitor similar to what is sometimes seen in FM detector transformers.

Joe

[mike hadley]

Hi Joe, I may be re inventing the wheel here, I have posted enlarged top and bottom chassis images from the aw15 worksheet, they can be printed up to a3 before they start getting pixelated.

Mike

[Joseph W Strickland]

After some further thought, I believe that the designation on the schematic at the IF transformers is simply identifying them as IF transformers. It is the only thing that makes sense.

As to the capacitor mentioned, it it probably on the inside of the coil form of that particular coil and may never fail. Unless one does fail, and someone replaces it, we may never know the exact value. For now I will leave the value indicated as 1200pF.

The illustrations of the internal connections of the tubes shown on the schematic are confusing as to which lines represent G1, G2 and G3 (signal grid, screen grid, suppressor grid). The suppressor grid is nearly always connected to the cathode, so that can be deduced from the illustration. The screen grid connects back to a lower B+ value than the plate circuit does, so that can be deduced also. We are used to seeing a more modern illustration of the internals of tubes, so that is what I am including in the redrawn schematic I am working on. I believe the more modern illustration of their internal connections is easier for most of us to grasp. Over the decades since vacuum tubes were developed and radios have been produced the standards for schematic representations of tubes has changed.

Mike;

Thanks for those nice illustrations. I had not seen those before. Is there a parts list that exists for these radios too? Component C, L and R identifiers are missing from the schematic too.

Joe

[mike hadley]

Hi Joe,

Here is the parts list.

[mike hadley]

[Joseph W Strickland]

Mike;

Thanks for the parts list. That is a big help!

Joe

[Joseph W Strickland]

Thanks to Mike his post of the parts list. I see that there is one 1200pF and one 1800pF capacitor in the parts list so that allows me to go forward with the schematic cleanup.

Joe

[mike hadley]

hi Joe,

Can I please have a copy when you have finished, my allwave fifteen is an early one with the wunderlich, but it has the two 1k resistors in the output driver stage grids, according to the circuits I have found there are no resistors in this position, my own intentions are to revise the nearest schematic to fit in with my chassis,

the illustrations are only part of the document I found, there is also a rather nice drawing of the turret, interested?

Mike

[Joseph W Strickland]

Mike;

Yes, it is the schematic with the Wunderlich tube that I am working on. The two 1K resistors in output stage signal grid circuits are there to help prevent RF signals from getting into the audio. The length of the audio leads between the radio tuner chassis and the power supply/audio output tubes is long enough to act as an antenna. It sometimes happens even with much shorter lead lengths.

Yes please do send the turret drawing.

I noticed that the notations alongside the Oscillator circuit coilsare the radio wavelengths by tuning band. At first I thought they were part numbers. It made sense when I looked at the installation and owner's manuals for the radio.

These are very nice radios and beautiful to display.

Joe