Just acquired first EH Scott radio, an Allwave 12, and have some questions.

[Troy Taylor]

Hello, and thank you for the opportunity to participate in this forum.  I have never signed up for a forum of any type before, so this is a new experience for me.  

I have been interested in vintage radios since I was 12 and received an RCA Radiola 18 from a junior high school teacher that was cleaning out his basement.  I have enjoyed the hobby ever since, and have always dreamed of finding an EH Scott radio I could afford.  Never thought it would happen though, but...  I'm 42 now and this past weekend that dream came true!  A long time collector friend offered me an Allwave 12 that was a duplicate in his collection and I brought it home.  

I have some questions about it though and I have posted some pictures of the chassis and speaker in my profile page.  Not sure how to link them directly to this particular discussion.  If anyone would be so kind as to take a look at the pictures and possibly know the answers to these following questions, I would very much appreciate it.

Please note: I have a degree in electronics, much experience with vintage electrical work (although not a radio expert), built my own vacuum tube stereo amplifier (6SN7 tubes in pre-amp and 807 tubes in the output), and am capable of doing my own restoration work.  I am very particular about retaining originality and only using methods and techniques that will meet the approval of well-respected restorers. 

I do not believe in modifying things or making any changes.  I strive to make my work appear as original as possible and not to leave anyone wondering about the quality or methodology of my approach.  That being said, my radio has been previously worked on by someone with a different view of things, and their work has me questioning what has been done.  So -that being said- Here goes with the questions:

>The power supply chassis has been worked on previously by someone that apparently discarded one of the capacitor cans.  Is it possible that these two replacements could be electrically equivalent to the three that used to be there, and that this is "correct" per the schematic, although cosmetically altered?  How would I go about returning this to it's original configuration?

>Where would I find the serial number?  Neither chassis has any plate or plaque on it that says "SCOTT" or anything else on it.  If this plate is missing, I cannot find any evidence of where it used to be.  I will be happy to contribute this number to the database if someone can advise me where to find it.

>Is this speaker correct?  The screws show evidence of having been removed/replaced and, although the plug looks correct and uses wire that definitely appears original, there are two extra wires hanging out of the speaker that have been clipped short and are just hanging loose.  They are visible in the photo as red and green wires sticking out on either side of the coil.

As mentioned, the collector that sold me this radio had a second one, and we compared the speakers between this one and the one he kept.  The speaker in his other Scott looked identical to mine, except without the extra two wires.  Neither speaker has any writing on it anywhere.  

Any information anyone can share would be most appreciated.  I intend to start restoring this radio as soon as I finish up a couple of other projects around the house that are occupying my attention, but I wanted to start acquiring information as soon as possible.

Thank you all in advance for any advice you may have.

Best regards-

Troy Taylor

[mike hadley]

Troy;

there is a solution to the missing cap in your power supply, my aw15 had the very same caps broken off at the mount,

i made a post a while back look for "screw mount caps" in the forum search.

mike

[David C. Poland]

Troy - Welcome to this website.

Your amp/power supply and the single speaker are correct for the Scott 2-DIAL circa 1931. There is no serial number as Scott began the serial numbers with the next model, the Scott DELUXE in mid 1932. Look in Archives at the top of the home page and then select set folders and then select Allwave (2-Dial)  . You will find information about your model and the owners manual you can print.

Your speaker may have been re-painted the correct color (brown) and the Scott decal is gone or painter over. the speaker was made by ROLA for Scott.

The Scott model 2-DIAL was the first of the chrome models of the 1930's, although the tube shields and coil covers are polished aluminum (Mother's Mag polish will shine them up almost like chrome plating). Your amp chrome looks unusually good.

The speaker plug has 5 wires.  2 wires to and from the single field coil. And other three wires are also high voltage - one to feed high voltage to the speaker mounted transformer center tap and the other two back from the output transformer to the plates of the two type 45 output tubes.  The audio signal from the tube plates go back on the same wires through the output transformer to the secondary winding to the speaker voice coil.  Perhaps the two wires dangling from the speaker are an attempt to use an auxiliary permanent magnet speaker - trace them out to see what they are connected to and likely remove them. 

As for the missing top side filter cap, look for a modern replacement underneath but I don'''t see any in your photo. The three are each 8 MFD and the small modern 10 MFD 450 volt film caps are suitable replacements electrically. I just add a terminal strip inside the amp to hold the 3 replacements filter caps. Leave the existing filter caps in place for cosmetic purposes, but disconnect them. 

Looks like you posted a rear view of the receiver, which has the 2 dials. Looks like a nice example.  The instruction manual should answer your questions about radio operation. This model uses plug in coils for short wave reception.  

[mike hadley]

Troy;

Polypropylene motor run caps are very good for filter caps, the DC rating is at least one and a half times the ac rating marked on the cap body. Unlike ordinary electrolytics the caps have a very long life.

Don't use motor start caps as they are intermittently rated.

[Troy Taylor]

Hello and thank you for the information!  I am wondering if anyone can confirm what console my Allwave 12 is in.  It looks most similar to the TASMAN model, except that all of the pictures I have seen of those have turned/round legs and mine does not.  I have not seen a picture of any cabinet exactly like the one I have.  A picture is attached now that I have figured out how to add them directly to this discussion.

I expect I will have more questions as time goes on; I am just trying to gather information before starting anything in the way of restoration work.

[David C. Poland]

Your cabinet is the PLYMOUTH. Yours looks very nice, with the original cloth, too.

Is one of several cabinets the buyer could select. Yours was $25 according to my Jan "31 price list.

You mention the TASMAN - it cost $18.75. Others cost more than the PLYMOUTH.

[Troy Taylor]

Hello-
This weekend I will be able to start working on restoring this AW12, with coaching and guidance from a retired tube-electronics guru that has 60+ years experience with radio repair and restoration. I have some questions before I travel to his house that I am hoping can be answered here.

I got started cleaning up and prepping the chassis in advance. There are a number of capacitors in metal cans labeled "POTTER". Some of these, as seen in the pictures, have a gooey brown residue on them, which I attribute to some sort of leakage. I assume that these will all need to be bypassed with new caps. What type/voltage rating is recommended for these replacements? And for my own knowledge, what type of capacitor is this originally called? They aren't electrolytic, wax, or paper as best I can discern.

Are there any 'hidden' caps or components somewhere in the chassis that I need to hunt for? Unless I am overlooking something, this looks like a very straightforward and easily serviced chassis.

I have already started replacing all the crispy/crunchy wires in the amplifier/power supply that have deteriorated insulation.

Oh and I am missing one of the shortwave coils, specifically one of the 38-84 Meter coils. Might anyone have a spare in a junkbox somewhere that they would be willing to sell me? I don't anticipate using the shortwave bands very frequently, but it would be nice to complete the set in this radio if someone has an orphan.

Thank you for any advice! I am really looking forward to getting this radio back into service.

[Troy Taylor]

Another picture.

[mike hadley]

Troy;

The caps marked potter are bathtub caps and will have to be either stuffed or bypassed,

the one in the photo is marked 1/10mfd, can be replaced with a 0.1uf capacitor, use polypropylene type rated at 600v, please check the other values before replacing,

the large box on the back wall of your main chassis, photo 8007 at the top of the image, the one marked potter will have a cap in, also the lower center of the chassis, the square box, yup this is a cap as well,

your photo 8006, the power supply, the tin box to the bottom left of the photo has a cap in, check the schematic for value,

as it hangs off of the dropper resistor I would rate this at 450v for safety reasons.

The main tubular caps in the power supply chassis will need to be replaced or bypassed, they will almost certainly be leaky by now, and if they go short will take out your ht transformer,

it's at this stage you have to make the decision of how far you wish to take your restoration,

keep chipping away and the job will soon get done.

Mike

[Norman S Braithwaite]

I believe those three smaller bathtub capacitors on the back apron contain the cathode chokes as well as the cathode bypass capacitors.  If so, the DC resistance between lugs will be very low.  The cathode bypass capacitors will be between one lug and the case.  The voltages to which these capacitors are exposed is low and it is unlikely that leakage will impair performance of the set to any significant degree.  Some of us leave them in circuit and others open them up and replace the wax-paper capacitor inside.

Norman

[mike hadley]

Troy;

Here is a picture of one of the bathtub caps with the choke in, this is from an allwave fifteen, your caps will be similar,

you will have to drill out the rivets out if you intend to do any work on the bathtubs.

Looking from the back of the bathtub, the cap is the long cylinder to the left and the choke to the right, the box is filled with pitch.

The capacitor choke junction is marked with a red dot of paint next to the lug, the other end of the cap is internally connected to the case,

the back can be removed with a soldering iron, be careful of the choke wires as they are easily damaged.

Mike

[Troy Taylor]

Hello-

Thank you for the advice; I availed myself of it this weekend as I got started restoring this radio. I replaced all the crispy wiring in the amplifier/power supply chassis first, then replaced all the capacitors. The metal cans that originally held the 8mf caps are later replacements. There were only two on the chassis as one of the cans contained two caps. These replacements were old/leaky, so they have been bypassed. I also replaced the 2uF cap directly off the big resistor. The power supply works great now! But, cosmetically, I am in need of 3 capacitor cans that are appropriate to this chassis. The two I have are not alike and I would prefer to have all three match.

In the radio chassis, I found that my bathtub caps did not contain any chokes. DC resistance ranged from over 15 megohms to open circuit. Since I did not want to damage anything by drilling rivets, I bypassed all these with modern .1uF and .47uF caps rated at 630V. All of the original dogbone resistors measured within 5%, so I elected to use them.

I brought the chassis up on a variac and the radio works! I am listening to it now. I have a Xerox copy of the instruction manual that explains the "LOCAL-DISTANCE" switch. At present, in the MEDIUM position, stations sound really good and have great volume. Switching to the LOCAL position completely cuts out the station that was quite strong in MEDIUM. I can hear and tune nothing in LOCAL position. After switching a clear station from MEDIUM to DISTANT position, both strong and weak stations are noticeably quieter than MEDIUM.

Where would be the best place to start troubleshooting this problem?

Also, I discovered that the original 100K volume control potentiometer had been replaced with an 800K. I have a newer 100K replacement in there now, but I don't think it is audio taper. Does anyone have a suggestion for a suitable new potentiometer that is high quality and will fit correctly?

Lastly, while sitting here listening to a station that is relatively weak in my area, I am noticing the volume is drifting up and down slowly. I did not notice this with a strong station. Could this be something I need to troubleshoot in the radio, or could this just be the nature of broadcast AM at night, subject to atmospheric conditions?

Thank you all again; I am really excited about getting this radio back into service again and look forward to any more advice!

Best regards- Troy

[Troy Taylor]

I think the antenna I am using may be responsible for my LOCAL-DISTANT switch problems. It is a 1920s vintage tabletop model, a diamond/God's-Eye shape with many wraps around the arms. It measures 28" across. Just by putting my hands on the wires I can improve the responses on this switch, so I think I need to get busy and string an antenna in my attic rafters.