Allwave 15 in Tasman Cabinet Electrical Restoration

[Jon Ketron]

Several months ago I was able to purchase an AW15 housed in a Tasman cabinet.  This beautiful receiver is somewhat special as the tuner chassis is still riveted after all these years.  I picked up this set in Kansas City.  Quite a drive for me, the price was right and worth the effort.  The previous owner was a radio collector.  This AW15 and a poor condition AW23 were all he had left.  A very nice fellow, I asked were he picked up the set.  He stated the receiver had been in his possession for quite some time, purchased from another radio collector back in the 1990's in Wisconsin.

As to the riveted tuner chassis.  There is a cardboard sleeve located on one of the electrolytic cans. Learning from fellow Scott collectors and research, this cardboard sleeve signified a prior E.H. Scott repair, meaning this receiver was brought back to the Scott factory for repairs either during the 1930's or early 1940's.  These tuner chassis were originally riveted shut once they left the laboratory.  E.H. Scott offered a 5 year warranty on all his receivers.  The warranty would become void if someone removed these rivets or tampered with the set.  After this AW15 had it's repairs completed, the laboratory installed new rivets.  The tuner chassis has not been opened since.  A true time capsule.

What makes things even more interesting:  The antenna post set up would indicate this machine to be an early version AW15.  Dave Poland had mentioned the toggle switch on the far side looking at the back of the receiver was a two position tone control of sorts.  In place of the Wunderlich tube resides a #58 tube with grid cap lead.  The socket is not labeled with a number.  The Sensitivity control escutcheon shows 5 positions.  I can only turn the control three positions (will look into this further once chassis is opened).

My consensus would be this receiver either was a transition from early production to late production, or received these modifications once the receiver was brought back into E.H. Scott Laboratories for repairs.  I must note; there is a #450 inscribed on the inside of the power supply.  This too signifies prior E.H. Scott repair.  It is interesting to think about these variables as the AW15 model in general went through so many changes during it's year long production run.  I would greatly appreciate any input you might have on this matter.

I find it interesting that the 2A3 output tubes are of the Arcturus brand, test 90% percent emission with no shorts.  No way these could be original unless this set was not used often or these are replacement tubes.  I should have the results of the power supply shortly.

Jon 

[Y2K Bruce]

Your speaker has the valuable cast basket and cast rear bell can also with the middle rear bolt down low. The other lesser valued similar speakers use a middle bolt through the center of the rear bell cover.

I believe the Asians covet the cast bell versions when they buy these on Ebay

[Jon Ketron]

Thank you Bruce.  I don't believe in parting out these magnificent sets for monetary value unless the set is beyond salvageable.  Even then, I tend to keep a small stock of speakers on hand as you never know when one may be needed for an outstanding project or new acquisition.  A sad state of affairs these days with Capehart, McMurdo Silver, and E.H. Scott sets.  I like the finish and look of this version 12'' Jensen compared to the earlier version often seen on the late AW12 sets.

Jon

[Jon Ketron]

With the power supply and speaker finished we move on to the tuner once again.  I changed things up and decided to tackle the top side first.  All coil shields were removed, .025 MFD capacitors changed out with brand new components.  Very interesting to note:  The variable tuning condenser sits on a lead plate!  The inside of the tuning condenser chrome cover is also lined with lead!  Such a feature insures no interference or reverse radiation from anything!  Another feature that just goes to show E.H. Scott radio units were the best of the best back then!  No wonder E.H. placed an AW15 within an elevator motor room during the Chicago Worlds Fair in 1934!  Such was an excellent demonstration of the AW15 capabilities, not to mention placement at said location during the Worlds Fair was an amazing marketing strategy!

All top side chrome has been polished, stunning to look at!

Jon

[David C. Poland]

Note on Jon's AW-15 receiver:  the early AW-15 Wunderlich AVC sets with the pair of red antenna posts -   the toggle switch in the back apron of the receiver is an antenna switch.

For a single long wire antenna, use the BLACK antenna post and have the toggle switch UP.

If using two antennae per the early AW-15 instruction manual, a) connect the long wire antenna to the black post and b) connect the transposed shortwave antenna twin leads to the RED posts - and put the toggle switch DOWN.  The owners manual for the early AW-15 Wunderlich sets has an illustration. The transposed SW antenna shows each half at 25 to 50 feet. And no particular length for the separate longwire antenna for the broadcast band.

The later AW-15 sets dropped the two red antenna posts and apron toggle switch -  and in their place Scott supplied  the  new Scott Supper Antenna (a double dipole antenna) with its twin lead to be attached to the round outboard chrome plated antenna switch, normally mounted on the 2nd IF tube shield.  Available for older Scotts for $7.50.

This version Scott Super Antenna continued as a $7.50 option on the price lists I have for the AW-23 into late 1936. For an AW-23 with a single antenna post, this Scott antenna with outboard antenna switch is appropriate. In Fall 1936, the AW-23 was revised with the new internal Supershield Coupling System and with two antenna posts, obsoleting the outboard antenna switch.  

[David C. Poland]

Concerning circuit diagrams. Riders service volume 14 has only two AW-15 diagrams, marked early and late, both using the 55 tube for 2nd detector. Three other factory diagrams have surfaced for the AW-15.  All three use the Wunderlich tube for 2nd detector. Many changes as the AW-15 evolved from April 1934 to Spring 1935. An informal comparison of AW-15 examples a few years ago among several of us yielded 7 variations of the AW-15 model. So, it can be helpful to refer to more than one of the five diagrams during a restoration. See the set folder for AW-15 in Scott Info Archive.

There is also a Scott factory recommended modification of a Wunderlich tube Scott (AW-12 or AW-15) to use the 55 tube, on account of the Wunderlich tube becoming unobtainable. Another approach seen in an AW-15 that I acquired was to connect the grid cap of a 55 tube with a wire to one of the 55's diode tube pins, leaving the set unmodified, but I cannot speak to the success of this approach.

More recently, some Wunderlich tubes have surfaced for those who need one.

[Jon Ketron]

Dave, thank you for this additional information.  It is interesting to note that this particular receiver was sent back to the Laboratory mid to late 1930's for several "updates": 

The Wunderlich tube had been replaced with a type 55.  Grid lead and cap are protruding from top of socket. 

There is a screw preventing sensitivity control moving past position #3.  The escutcheon shows 5 positions, only three can be obtained!

Due to lack of Wunderlich, the 1st Audio HT decouple capacitor was disconnected.

Presence of orange Potter wax capacitors within circuit.

Several extra "bath tub" capacitors can be seen within circuit.  These are not riveted, yet bolted to tuner chassis.

Jon

[Jon Ketron]

The underside of the tuner chassis is now complete.  All capacitors have been changed out, minus the three I.F. filters containing inductors.  These three capacitors were tested with a capacitance meter.  All three held steady upon rated voltage applied and have been left in circuit.  All resistors minus one checked within a 15% tolerance thus most all were left in circuit.  All electrical contacts have been cleaned.  Coil wheel cleaned and lubricated.  Everything on the tuner underside is now complete.  Time for a first post-restoration power up!

Jon

[Jon Ketron]

The tuner chassis, power supply, and speaker are now complete.  Everything was assembled upon the work bench.  A first power up of the set post electrical restoration was a success!  Alignment was checked and set was monitored for 10 hours under normal operating conditions.  This AW-15 is now complete, looks and sounds stunning out of the cabinet!  Note:  I was careful with the speaker volume.  Never a good idea to turn up speaker volume out of the cabinet as doing so can damage the speaker!

Video of the set playing out of the cabinet:  https://www.youtube.com/watch?v=FQRz_0hWiI8

Jon

[Jon Ketron]

All components were put back into the Tasman cabinet this morning.  Prior to doing so, the cabinet had been cleaned and polished with a micro crystalline professional archive polish.  No fingerprint residue from this special polish I use!  Luster from polish is amazing.  Conclusion:  Overall performance of this AW-15 (just like the last one completed) is phenomenal.  Sound quality is superior to at least most all mid 1930's radio set's that have ever come across my bench in the last 12 years.  Opinion:  Once again E.H. Scott comes through as one of best for 1934!  Build quality and performance is just amazing, surpassing most all receiver sets available to the general public radio market in 1934.    

Video of the AW-15 playing inside the Tasman cabinet:  https://www.youtube.com/watch?v=ysLyawgahxo

This project is now complete.  Thank you for your patience in concluding this topic!

Jon

[Thomas Day]

Jon:

Thanks for the demonstrations. There is something about listening to 1930's music on a radio from the era. Our local station WBBM plays old radio shows on Weekend nights. Sound wonderful on my Allwave 23. This now inspires me to actually take my radio back to the bench and do a complete re-alignment. I did a re-cap and new power transformer when I got it. I have the Waverly cabinet, and the condition of the cabinet and chassis are excellent. A friend recommended Kiwi Neutral shoe polish for the cabinet finish and it works very well. 

I also have a later Alllwave 23 chassis only, but it has been seriously modified by a previous owner. It is the dual antenna post model, but before the 7 knob version. 

Thanks again

Thom

[Jon Ketron]

Thomas,

Thank you for commenting and following along.  You are most welcome for the demonstration videos.  Regarding the internet, good solid demonstrations of these E.H. Scott units in action are few and far between.  Those individuals who may not own an E.H. Scott model have the opportunity to see such a set in live action.  Placement of the AW-15 components back into the Tasman cabinet enhanced overall audio quality (as expected) of this AW-15.  In my opinion, you almost have to hear one of these sets in person to take in the full audio spectrum the set has to offer.  I have had several opportunities to listen to AW12's, 15's, 23's, as well as Philharmonic's and one AW27 within other collections.  All live demonstrations just sounded wonderful.  E.H. Scott receivers were truly in a class of their own back then.  I wish I could demonstrate more sets via YouTube and just may do such in the near future.

Thomas, I tend to transmit period music over the air daily via several part 15 transmitters I own.  I do feel that it does temporarily take us back to the times these set's may had been used.  Perfecting alignment on any radio is a must.  I encourage you to do so!  I am still learning with regards to aligning E.H. Scott receivers.  So far I have only had to tweak very little on all E.H. Scott restorations I have come across to date.  The laboratory made adjustments upon the sets being built.  I try my best to leave such adjustments alone when and if possible.  Very nice to hear you own an AW23 Waverly example.  I will be documenting an 7 knob AW23 Waverly set here on the forum in the near future.  Thanks for commenting!

Jon