EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

What is the value of the two electrolytics on the Allwave 15 tuner chassis? I have tried enlarging the print of the schematic on the info site, however, it is still too small.

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Thomas,

Depends on the version. You refer to the two electrolytic cap cans on the front right corner of the receiver which are tied to the higher voltage B+ circuits off the big voltage divider. Do leave the old electrolytics in place for sake of appearance, but disconnected.

The later production sets with 55 detector and just the single antenna post and ground post, the diagrams say 8 MFD, So a modern 10 MFD cap is appropriate for both caps.

The earlier production Wunderlich detector sets (also identified by the additional 2 red short wave antenna posts) are 3.5 MFD according to the diagrams. A modern 4 MFD is appropriate for both.

If yours has a 55 detector but 1) the that tube socket has no tube number embossed and 2) has the additional pair of red antenna posts, then you likely have a set converted to a 55, after Wunderlich tubes became scarce. So use 4 MFD caps.

-Dave

At what point were these electrolytics eliminated and the chassis not punched?

Never seen one, except for the battery/farm version.

Interesting and most helpful information, I thank you for submitting it. After receiving it, I felt that close examination of one of the schematics was necessary.

Version here is with 2A7(marked tube socket) and 55(unmarked tube socket), plus antenna posts as you mentioned.

On further examination of the AW15 schematic dated 19 November 1934, with a 3x loupe, it appears that this chassis probably left the factory with these tubes, antenna posts, and caps like you state. Since there are no 4mfd available to me, a pair of 4.7 should do the trick.

Thomas, Yes, 4.7 MFD (and what I meant to write).

Your AW-15 may have been returned to Scott Labs. At times, when a radio was returned for service, Scott might update an earlier version example to current/later production specs. If your receiver's right front filter caps is wrapped with brown paper tape with a number on it, it very likely it went back to Scott for service.

Remember, Scott was a custom set builder, made running changes, and would sometimes further customize a receiver for a buyer. Riders published only two AW-25 diagrams, both using the 55. Scott collectors have discovered 3 additional factory diagrams (so far) including some with the earlier Wunderlich tube Detector. But we have documented no less than 9 variations as the AW-15 evolved, so some examples may have details that straddle 2 of the diagrams.

Scott sometimes used fringe technology to design the best radio he could. During the period Scott used the Wunderlich tube for the 12 tube Deluxe and for the Fifteen, there is reason Scott tubed up the entire set with blue glass Arcturus tubes. There are only a very few radio models that used the Wunderlich tube other than Scott. The Wunderlich is a full wave 2nd detector and audio amplifier. The triode/dual diode 55 came out sometime after the Wunderlich and became the first widely used AVC tube.

For your radio, perhaps the Wunderlich failed when replacements were no longer unavailable. A number of radios were returned to Scott for modification to replace the Wunderlich with a 55. And in addition, there is evidence Scott sometimes made some other refinements while a radio was in for service - perhaps update the 1st detector of an early AW-15 from a 58 (or the later production 57) to the final production's 2A7 and change the tube socket too. .... Or perhaps Scott took in your AW-15 in trade towards an AW-23 or later model, and reconditioned the AW-15 to conform more closely to final 1935 production version AW-15 before reselling it. The AW-15 is a very good receiver, it just isn't high fidelity nor have the audio power of the AW-23 or later models.

If you inspect the grid cap wire hole for the 55 tube you may well see just a drilled hole in the chassis. Whereas, for my late version AW-15, the 55 grid cap wire come through a hole with a brass sleeve to better protect the wire. A brass sleeve would be difficult to install after the chassis has been built up. It would be an interesting project to restore an early converted model back to the original Wunderlich. I have compared a couple converted examples, and and I think the Wunderlich models are more sensitive and, so, I may yet covert back the one currently have.

Incidentally, there is a factory recommended modification to convert a Scott from a Wunderlich 2nd detector to the 55 tube for both the Model Fifteen (AW-15) and also for the earlier 12 tube Allwave Deluxe with AVC (AW-12). If someone needs of a used 2.5 volt Arcturus Wunderlich tube which tests good and which I have operated in a Scott, contact me.

3rd paragraph, 2nd line, meant AW-15 and i could not seem to edit it. - Dave



David C. Poland said:

3rd paragraph, 2nd line, meant AW-15 and i could not seem to edit it. - Dave

As far as those two electrolytics on the tuner, they appear to have light a coating of a brown/yellow tint. This coloring does not appear anywhere else on the set. No marking as to value or brand. Their tops are almost flat, no vent holes.

Any case, five new caps installed, back in the game. Listened to Radio UNAM 1060khz and Radio Publica (XRA) 1220khz last night in spite of local thunderstorms.

For the chrome, i like Turtle Chrome Polish (a liquid).
And those old electrolytic caps respond to polishing to remove the dirt, household residue and oxidation. They polish up almost like chrome. I like Mothers Mag and Aluminum polish - at your auto parts store. Really improves the the appearance of the receiver and the amp. Some of those caps do seem to have a lacquer coating which make polishing more of a challenge, but polishing still improves them.
-Dave

Thank you for the polishing tips.

Another polish to consider is, Met-all. As its name implies, capable of polishing many different metals.

Lost my head on those stations, Radio UNAM is 860khz, Radio Educaccion is 1060khz. It feels like I am a character in, The Legend of Sleeping Hollow, at times..

Further inspection of the grid cap wire entrance for the 55 detector, per your post of the 28th of April, reveals a drilled hole with no bushing.

One thing about this tuner chassis, other than the apparent detector change and fresh electrolytics, it does not appear to have seen recent service. In other words, original.

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