Tuning Can for Scott Allwave 15

[Michael J Boessen]

Hi, All:

My cousin from Arizona arrived yesterday at my place in Columbia, MO with a Scott Allwave 15 for me to restore.  Doing some preliminary reading, I see in the alignment instructions that there is a special IF can cover that must be installed do do alignment.  I don't have this, but I suspect I could fabricate something if I knew what it looks like.  Does anyone have one they could maybe provide me a photo and some measurements?

I have also read several posts here regarding the rotary band select mechanism, and some fairly hairy horror stories.  I would appreciate any advice anyone can give to keep me from falling into this pit.

Lastly, I have to replace some veneer on the front.  To my eye, it looks to be walnut.  Can anyone verify that?

I have already been warned that this will be a very challenging restoration, with a lot of hard lessons to be learned.  I'm hoping you guys can ease the pain a little.  This belongs to a very dear cousin, and I want to send him back a nice, properly performing radio.

Any help greatly appreciated

Best

Mike

[Michael J Boessen]

Thanks, David!

I was surprised to get a quick reply to an ad I placed on ARF for 2 of the filter units.  The part numbers are a little different, (mine are 8391 and his are 8031) but possibly just earlier versions than mine.  The guy is sure they are from an AW15.

I also need to thank you for a comment in your last post to "watch for the detent balls" in the tuning mechanism.  Mine didn't really have a "detent feel" as received, which I found a little disturbing.  Upon removing the wheel, I see that a previous servicer apparently lost the 2 springs and detent balls.  I'm sure I can find something in my vast stash of stuff to do an adequate job.  

Really appreciate the help!  Can't thank you enough.

Best

Mike

[Michael J Boessen]

Hi, David:

Well, I went to the Allwave Deluxe (12 tube) and went through all of the folders there.  I didn't see any help for relating the numbers on the chassis diagram to the schematic.  I'll just cross that bridge when I come to it.

I thought this detent ball thing would be no problem, but it has turned out to be problematic.  I've tried 3 different spring tensions, and 2 different ball sizes, but not getting it to work.  A ball that fits the sockets seems to just jam the thing.  A larger one doesn't let the wheel go all the way down.  I'll keep fooling with that as well.

I am corresponding with the guy on ARF that thinks he has these filter units, but am having trouble establishing that they are the correct part.  Is there any chance you could help me figure out where these are on the schematic?  That would help me a lot with deciding if I can compromise.  I'm waiting for him to give me resistance readings across the terminals on the ones he has.  I  might need to contact your guy.

Thanks again for the help.

Mike

[David C. Poland]

Look at the diagram for the separate cap and coil between the cathode and ground. Would have been helpful if there was a dotted line surrounding these two items to indicate a unit part. Trace the wire to confirm. 

[Michael J Boessen]

OK.  The "late" version diagram I'm using shows a cap and resistor in those IF cathodes.  I'll look at some of the other diagrams and see what I can find.  

The guy on ARF found the same resistance between the terminals on these filter units as mine read, so I'm going to gamble and pay him for them.

I can't get the detent patent to work.  I have asked him if he has the factory parts.  Hope he does...

Thanks again for all the help.

Best

Mike

[Michael J Boessen]

Hi, David:

Radio is playing great on the bench right now.  Very amazing.  I haven't fooled with anything yet.  Just finished the chassis rebuild.  I feel embarrassed to have to ask this, as you may have told me already, but the operating instructions I have are for the power chassis with the 2 fuse locations. Mine has the switch and I can't find the instructions for that.  Can you tell me which way that switch goes?  I believe I have figured out that it should be "up"  for voltages above 110, but I would like to verify that before leaving it on for an extended period.

Thanks

Mike

[Thomas Day]

For the coil wheel detents, they are a spring and cup assembly, not spring and ball.. This same setup is used in the Allwave 23. I managed to lose one set when I rebuilt my second Allwave 23..I was able get a replacement from a list member. 
Thom. 

[Michael J Boessen]

Hi, Thom:

Well, that explains a lot, because I fooled with it for a long time with the various springs and balls.   I found a guy on ARF that had the coil-cap units I needed and also the correct detent parts.  They should be here about mid week.

Thanks for the info!  The radio plays great.  It amazes me how loud I can crank it without distortion.  The speaker is apparently a very good design, as well as the audio circuitry.  I have a Zenith 12S569Z with push-pull and a 15" speaker.  It is the only radio I have ever worked on that can compare to this Allwave 15.

Best

Mike

[Thomas Day]

I have the Allwave 23 with the quad 2A3 power amp. One quarter turn of the volume control is all you need, anything more will be way too loud.

Thom. 

[Michael J Boessen]

Yep.  It's the same with my Zenith.  But it's a lot newer.  It is amazing what these Scott guys accomplished this early in the game.  That AW23 is about the pinnacle of AM radio.  I think the 3 best AM radios ever made were the AW23, the McMurdo Silver Masterpiece 6 and the Zenith Stratosphere.  I've never even seen the Zenith or Scott.  I once had a McMurdo Silver Masterpiece 6.  I was missing the Clifton cabinet and the power chassis.  After 2 years of not being able to find a cabinet, I finally sold what I had.  Kind of wish I had made a different decision.

[David C. Poland]

The speaker is a theater speaker, by Jensen, and customized to Scott's specs and with 2 field coils. One in B+ circuit, the other in the bias circuit for the output tubes.

The amp should have a high-low switch, adjacent to the Jones socket. In the 1930's house voltages were less consistent and might range from 100 volts to, say, 125 volts city or country and maybe time of day.

Today's higher AC house voltages usually over 115 volts. Indeed I usually see upwards to 122 volts AC. So, the toggle switch  should be in the up position, which dims the tube filaments and dial lamp so the set runs cooler and keeps the B+ voltages in the intended range.

Yes the AW-15 has plenty of audio power with a decent input signal. Good frequency response, but falls short of being high fidelity. The next Scott model AW-23 of 1935-37 is high fidelity with the optional tweeter pair. By then there were experimental high fidelity radio stations in some larger cities (St Louis, Chicago, Los Angeles...) and the AW-23 was built to take advantage of theses broadcasts, wider band width stations allocated to the top of the dial, above 1500KC. Static free FM broadcasts still were in the future, starting in 1940, and considered experimental before WW2.

[Michael J Boessen]

HI, David:

What you have just said makes me want to ask a question.  I have had several low end 4 and 5 tube early 30s radios that I could never make the sound as good as I thought it should be, especially at the higher frequencies.  Even at low volume settings, they just didn't sound good.   Is it possible that they just don't have the bandwidth to handle modern broadcasts?  On one or two of them I spent an inordinate amount of time, even changing speakers.  Could this be why?

Thanks for verifying the switch position for me.  I was a bit worried about that.

The broadcast on this AW15 is amazing.  The short wave, by contrast, is just plain awful.  I could pick up one station about 12 mhz and nothing else.  I'm going golfing tomorrow.  I will undertake an alignment Friday.  I have my soup can covers all ready to go.  That said, this is too poor to be alignment.  Do you have any thoughts for me regarding very poor SW sensitivity?

Thanks a lot for all of your help.  Saved me a lot of time and angst.

Best

Mike

[David C. Poland]

Precious few short wave stations now days. The days of numerous stations like Christian Science's Monitor Radio or Voice of America are long gone. What I mostly find daytime is a few US mostly religion broadcasts.

Wait for evening after the ionosphere re-forms - reflects (bounces)  radio signals, when you get some foreign short wave stations - evenings from Europe like BBC and Germany. Also Russia and maybe China's English broadcasts. Also South America and even Australia.  Try around 5 MC, 7MC and 10 MC as some portions of the AW band are for radio stations, and others are reserved for ham radio, radio beacons for airplanes, etc. Be sure you advance the sensitivity control.  On the short wave bands, tune SLOWLY, like advised in the owners manual. SW stations beam broadcasts to desired direction, and may sign off one frequency and change to another to resume broadcasts, and often broadcast simultaneously on more than one frequency. 

Be aware on the Broadcast band, that daytime broadcasts will be limited to local and nearer regional stations. Stations power varies widely, from 250 watts many of which sign off at dusk to the big clear channel regionals with 50,000 watts. For example, numerous 250 watt stations use 1230 KC (more than 3 in Ohio). Only 50,000 watt WLW in on 700KC. Again the ionosphere forms after dark reflecting station signals and, so, many stations are required to sign off to reduce interfering with others at night.

Also, stations below about 1000KC carry better, and higher not so well. 

Best to have an outdoor long wire antenna, 50 to 70 feet including lead-in is plenty. Some of the static you hear may be from inside your house - wall warts, florescent lights, dimmer switches, electric clothes dryer, electronic voltage transformers for 12 volt decorative lighting, ...

Also WWV for National Bureau of Standards, Ft Collins Colorado, at 5 MC, 10 MC and maybe 15 MC for the time on the minute, with clock beat every second between, depending on atmosphere conditions. Canada also has a time broadcast around 7.5 MC as I recall.