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;

You certainly seem to be getting there, I mentioned before a method of replacing the large psu caps,

I can send you some empty cap shells if you wish,

posting here

http://ehscott.ning.com/forum/topics/screw-mount-caps

Is this any good?

Mike

[Troy Taylor]

Hello Mike-

Yes, I would like to buy 3 matching empty capacitor shells from you.  I have only 2 at present, and they are mismatched.  One of them has the values stamped into it, so that won't polish out either.  The modern caps are so small that I was able to fit them into the chassis even without the cap shells, so these will be cosmetic.  How do I go about buying them from you?

I am listening to the radio now -I really enjoy it, and Seattle has 880 AM KIXI, which is a great station!- and am noticing that the volume is a bit unstable.  It occasionally changes itself rather dramatically.  I can't tell if this is from the rather cheap 100K pot in there, a temporary replacement until I can find a high quality one to use, or if there is something in the circuit and/or tubes I should be investigating.  As I typed this, it did it again.  The change is quite abrupt, not gradual.  It cut in half in the blink of an eye right now.  Any suggestions?

Thank you all for the advice!  I am very happy to be listening to this radio again!

-Troy

[mike hadley]

Troy,

Try checking your tubes, gas and low emissions can cause funny things to happen, one of the 58 tubes in my AW15 hissed like an fm radio between stations,

If your signal is drifting up and down slowly it maybe conditions,

try putting a signal generator in another room, this will give you the same type of signal as a distant station, you may have to attach a short wire to the generator, maybe a couple of feet maximum,

I have never tired a Scott on a loop antenna, you should have at least 50ft of wire, Scott recommends 80ft,

good luck

Mike

[Thomas Day]

Troy:

The antenna you are using is directional. You can rotate it for best signal from the station.

[Troy Taylor]

Thank you all for the advice.  As I am going through and cleaning things up on the chassis I am starting to notice details I didn't pay attention to before.  I discovered that the dial lamps were rewired at some point in the past and one of the lugs had a big glob of solder on it that was occasionally arcing slightly to the chassis.  Would make the lamp dim and have a soft audible crackle.  That has been taken care of now.

Now I have a new question though.  On the back side of the right hand (as you face the radio) tuning condensor is an antenna post and a grid wire with a cap on the end.  I believe this is for shortwave use.  But it looks to me like it has been modified by someone in the past, since the resistor in there is not 1930s vintage, and there are some lugs that show evidence of formerly having something soldered to them but no longer do.  Attached is a picture of what it looks like now.  Could anyone please provide a photo of what these components are supposed to look like?  Please note that I removed the tube shield from the nearest tube for clarity; it is not missing.

I have been listening to this radio regularly now.  Stringing a long wire antenna down the hallway to the farthest wall of my house helped with reception, but I really need to get busy and string up some wire in the attic to do an even better job.

Thank you and best regards-

Troy

[David C. Poland]

As for volume stability, the volume changes you mentioned, check the operating condition of the volume control. With the radio off, disconnect the center lead. Then attach a meter to determine if the resistance changes smoothly. If not try some contact spray. Note - the volume is controlled not like the more modern radios placed in the audio circuit. Rather, it controls the screen grid voltages, thus changing the RF and IF gain.

Yes, a dial lamp short to ground will produce a buzz in the sound.

The amp has a HI-LO switch, put in the HI position (for higher line voltage- so the tubes and dial lamp run cooler (less bright) to prolong tube life and reduce set's high voltage a bit,

The instruction manual has instructions about that other grid cap, and use of the short wave coils. Note also that for some short wave coils, the coil cover is removed. 

For your next Scott, suggest the single dial models - with the 12 tube Allwave Deluxe 1932-33) or the 15 tube model Fifteen mid 1934-mid1935. BC and SW coils are mounted on an elegantly designed coil wheel inside. Much nicer to operate than the two dial model.

[Y2K Bruce]

TROYS TRAVAILS got me to take out again my Scott dual dial AW12and figure out why I had no sound.

It was recently electrically restored by a skilled friend and once home here I was unable to get sound. It traced down to needing a long antenna but most of the issue is the large chrome can over the left side plug in coil.

When installed I get zero sound or reception but when the big can is removed the set plays and sounds very good and loud.

Am running it now on a 105 volt stepdown Bucky box.

[Troy Taylor]

Hello-

As I continue to use and learn more about this radio now that it is functional, I keep finding new questions.  I have a low-resolution/quality Xerox copy of the original owners instruction manual.  In the section labeled "TUBES", it says to interchange the type 27 tubes around until you get the loudest signal from whichever tube is in the second detector socket.  The manual also recommends trading tubes around if you are experiencing any problems requiring troubleshooting.  In the RECEIVER ONLY, is it safe/acceptable to trade tubes around while the power is on?  The manual is not clear, but turning the set on/off to swap tubes around seems like it would make it difficult to recall which one produced the loudest signal.  As such, I have not yet attempted to trade tubes around to find the 'best' one for that socket.

I find that the left hand dial (oscillator circuit) is very selective.  But the right hand dial produces audible reception on any given station across a very broad range.  For example, I can hear a station on 880KC from about 800-950KC with the right dial.  It is not uniformly loud/clear, but that seems like quite a broad range to be able to hear the station at all.  Is this normal operation?

Also- my instruction manual is a poor quality Xerox copy.  Has anyone reproduced a high-quality copy of the original manual that I could buy?  I've seen some truly excellent reproduction manuals for player pianos and phonographs, so if anyone has done this with the 2 dial AW12 Scott, I'd be quite happy to buy a copy.

Thank you and best regards-

Troy

[Troy Taylor]

Hello and Happy New Year-

I have been using this AW12 regularly for the last couple of years, using an _excellent_ quality bucking transformer I bought from another forum member.  The radio has been working great, until a short while ago.  Now it has blown a couple of fuses in the bucking transformer (not any fuses in the radio itself).  It blew a 3A fuse in the smaller transformer I use, and also a 5A fuse in the larger transformer I typically use to operate the AW23.

The fuses blew at power up, but not immediately.  First the dial lights came on fine, then a sort-of a slight hum, then POOF went the fuse.  This happened before the 80 would have warmed up enough to be supplying DC to the set.

I checked the 80 and discovered it has an open filament.  Since I've been using this set for a couple of years with this same tube, obviously the tube recently failed.  But I am now wondering: would a dead rectifier tube cause an increase in current draw when powering up, such that the rectifier failure is the cause of the fuses blowing?

Or- might some other reason for an increase in current draw also be the cause of failure for the 80? 

I'm trying to figure out if the failed rectifier tube is the cause of my fuse-blowing problem, or a symptom of something else going on, before I potentially blow any more fuses or 80s. 

Thank you and best regards-

Troy

Edmonds, WA

[David C. Poland]

Suggest you replace the fuse and install another tested good 80. Power up with a Variac and see what happens.

Rectifier would usually either wear out (lose emission) or burn out.

If the filament failed with a broken filament, a loose end may have touched the plate, in which case the fuse did its job.

Initial power up surge is when a tube (or a light bulb) seems most apt to burn out.

[Kent King]

Do you have a variac? I'd bring it up slowly, monitoring voltage. Don't underestimate how quickly an 80 will start delivering B+, since the filament is the cathode, the voltage comes up very quickly. I'd be very suspicious of a shorted filter cap.

Kent

[Troy Taylor]

Hello-  It took longer than expected, but last evening I finally got a chance to investigate the power supply.  I could not find anything amiss with the filter caps or any other components.  So I replaced the faulty 80 with a known good one and powered up again.  Everything works again!  No blown fuses, no surprises.  I played it all evening last night and it is playing now as I type.  Just about to listen to "FIFTIES AT FIVE" on my favorite local station.

I guess the filament in the 80 went open without something else in the radio failing and taking out the tube.  Glad there were no serious problems to sort out.

Thank you all for the advice and suggestions!  Hoping to resume muddling through the Philharmonic this weekend.

Best regards-
Troy

Edmonds, WA