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 

[mike hadley]

Jon;

Once the chassis is opened, are you going to re-cap the chassis, if so are you going to stuff the bathtubs?

Mike

[Jon Ketron]

Dave,

Thank you for that bit of info.  With regard's to what you and Norman spoke of, it seems that this receiver would have indeed received several updates when it was returned to the laboratory for servicing.  Where the current type 58 sits on the Wunderlich socket, there is a red colored center button just as you state with no engraving.  No brass grommet where the grid lead protrudes from the tuner chassis either.  I will have to check the final IF transformer secondary and get back with you once I open the chassis.  I will conform to this set for restoration.  I really appreciate the advice and insight.  This is what make's E.H. Scott units interesting to work on and interesting to research as well!

Jon
 
David C. Poland said:

Jon - FYI -  There is evidence, that when a Scott radio was returned to the factory for service, that certain updates may be made to conform to current production.

That may explain the 3 position switch with the earlier 5 position escutcheon. The Wunderlich socket center button has a dark red color and no tube number I suppose to match the dark red Wunderlich tube base. You may find the original center tapped final IF transformer secondary with the ends wired separately to each of the two diodes in the 55 tube, or maybe not. A hole will have been drilled in the chassis for the 55 tube grid cap wire - in later post-Wunderlick production, that hole was sleeved with a brass grommet for the 55 tube grid cap wire, which brass grommet your set probably lacks. You may find the 1st detector tube changed from a 58 to a 57 or maybe a 2A7 and so on.

Ahhh -  hence the possible variations in actual sets compared to available factory diagrams and why it is useful to have available more than one diagram during a set restoration. My take is to conform to the actual set rather than trying to reverse older changes, especially with indication of factory made updates.

Wish you well with your AW-15 project. I, too, have what I believe is an updated Wunderlich to 55 tube set in my collection.

[David C. Poland]

Jon  --  Depending on what your visual inspection reveals on the 4th IF, maybe a 55 is appropriate or maybe reversion to a Wunderlick too, as I expect your example to still have the center tapped secondary on the final IF transformer..  

My experience with my AW-15 (with prior conversion of a Wunderlick set to 55 tube) seems to have  compromised the sensitivity somewhat. My  AW-12 Wunderlich set seems more sensitive than my converted AW-15. This Winter, I hope to deal with the the AW-15 Wunderlick set I recently acquired, then I'll have a better idea about the it.

[Jon Ketron]

Mike,

Thank you for your interest in this restoration.  I will only re-stuff those bathtub caps which retain inductors.  Meaning those three along the rear of the tuner chassis.  All other components will be by-passed with visible brand new parts.

Jon
 
mike hadley said:

Jon;

Once the chassis is opened, are you going to re-cap the chassis, if so are you going to stuff the bathtubs?

Mike

[Jon Ketron]

Thank you Dave,

Will be opening the tuner chassis soon.  Interested to see what the 4th IF reveals.  Thank you for posting performance evaluations with regards to the conversions made via the Laboratory.  It would be interesting to witness the differences in person.  The previous early AW15 Wunderlich serviced has since been returned to it's owner.  Sadly I do not have a factory early version to compare with at this time.

Jon
 
David C. Poland said:

Jon  --  Depending on what your visual inspection reveals on the 4th IF, maybe a 55 is appropriate or maybe reversion to a Wunderlick too, as I expect your example to still have the center tapped secondary on the final IF transformer..  

My experience with my AW-15 (with prior conversion of a Wunderlick set to 55 tube) seems to have  compromised the sensitivity somewhat. My  AW-12 Wunderlich set seems more sensitive than my converted AW-15. This Winter, I hope to deal with the the AW-15 Wunderlick set I recently acquired, then I'll have a better idea about the it.

[Jon Ketron]

The power supply has been completed.  All capacitors, resistors, and electrolytic capacitor's have been changed out.  Brand new components have taken place of the old ones.  I went with terminal strips this go-around.  I also polished the chrome with "Turtle Wax Liquid Chrome Polish".  Excellent results.  I have yet to come across a visually perfect power supply with no corrosion.

Jon

[Jon Ketron]

Time to open up the tuner chassis.  It is important to note this tuner chassis has been sealed since at least 1939 or 1940.  Depending on when the set was purchased brand new, the 5 year warranty would have expired right around this time frame.  The first picture shows the bottom cover.  Notice the #3003 written in pencil.  This exact number is stamped on the cardboard sleeve attached to one of the electrolytic capacitor cans on the tuner chassis.  After carefully grinding off both rivets, we are now inside for the first time in at least 77-78 years!

More detailed pictures to follow.

Jon

[Jon Ketron]

The second cover has now been removed.  I see two "Potter" wax capacitors (second one underneath the coil wheel).  I have had trouble locating these on the schematic thus far.  I am thinking with the modifications performed on this chassis and utilization of a type 55 tube as Norman stated, I will be referencing the late model schematic.  Need to compare and reference further.

Question:  I have seen these orange "Potter" wax caps in several AW23 chassis.  Were "Potter" brand wax caps used on the Philharmonic chassis or any chassis for that matter past 1937?  Perhaps the use of these "Potter" wax caps can date the modifications completed on this AW15 to the years 1936-1937, when the AW23 was offered through E.H. Scott? 

Jon

[Norman S Braithwaite]

EH Scott Radio Laboratories discontinued the use of Potter capacitors relatively early in the production of the AW-23.

Norman

[mike hadley]

Jon;
Interesting to note that the bathtub filter to the right of the power umbilical (next to the antenna switch) only has the capacitor side connected and not the inductor, so this can't be wired as a filter, it will be interesting to see how this ties in with a schematic.
Looks like Scott has done it again!

Mike

[David C. Poland]

Jon - be careful with that powder coating on those bathtub caps. I always wipe away with damp paper towels and avoid direct skin contact - likely the harmful corrosion surface of cadmium coated metal.

[Jon Ketron]

Thank you Norman.  With your provided information, seems we can perhaps date these modifications and chassis repair to 1936.  An opinion and merely speculation form the facts already on the table:  This set was purchased in 1934, went back to the factory for repair and modification in 1936.

More pictures with the coil wheel removed provided below.

Jon
 
Norman S Braithwaite said:

EH Scott Radio Laboratories discontinued the use of Potter capacitors relatively early in the production of the AW-23.

Norman