1934 AW 15 Electrical Restoration, Questions Please

[Jon Ketron]

Hello all,

I am new to this forum and somewhat new to E.H. Scott Radios.  I have about 10 years experience collecting, restoring, and rebuilding pre WWII radio's back to factory specs., or as close as possible.  I am excited to start an electrical restoration on this early version AW15.  My goal is to re-stuff each and every bathtub style capacitor which will include drilling out each rivet and re-installing new rivets.  I will also re-stuff all electrolytic cans.  The end goal of this restoration is to have an electrically restored factory looking set.  

Has anyone re-stuffed these bathtub style caps before?  Could you please give me any pointers or advice for this procedure?  What style of rivets are used for re-installation and what would be the best tool to use for this as there will be many awkward angles?

You may notice the Olympian cabinet this radio resides in has short legs.  Upon close examination, Norman and myself have decided this cabinet had a new set of legs and stretcher installed at some point during the radio's life.  Whether at the beginning or sometime mid point, I don't know.  The legs and stretcher look to be a custom job and the quality shows as this modification looks to be neat and very difficult to spot upon preliminary inspection.

I would like to thank all of you for any help provided, this looks to be an excellent forum!

Thanks,

Jon

 

[Jon Ketron]

Thank you Norman.

Jon
 
Norman S Braithwaite said:

The bandswitch gear boxes employed in the Allwave Deluxe, Allwave Fifteen, and Full Range High Fidelity (AW-23, AW-27) receivers are chrome plated pot metal.  Most were cast using a good alloy but some made during the run of Allwave Fifteen receivers were cast using a bad combination of ingredients.  The broken stop on your gear box is likely due to a combination of a marginal alloy plus an attempt to rotate the bandswitch too far.  It will likely work satisfactorily if you cement the stop using two part epoxy.  If you want to replace the top piece of the gear box or the entire gear box, I have good ones available.

Norman

[Jon Ketron]

Thanks to Norman sending me a good condition gear box, the top plate of the original has now been replaced.

Jon

[mike hadley]

Jon;
Looks like the big day is getting closer, you say this set belongs to a friend, I think that if it performs anything like my aw15 you will have a real problem giving it back,
Good luck with the final parts of the restoration, we a are all curators with these sets hopefully passing them on for future generations to enjoy.
Mike

[Jon Ketron]

Thanks Mike, the set is actually finished.  I am continuing to update this discussion topic as we speak.  I have an early AW15 Tasman and a late 7 knob AW23 Waverly patiently awaiting restoration, so thankfully I won't be without a Scott.  It is the only working Scott in the radio room right now though, wish I could hold on to this set for a bit longer and enjoy it!  Blow's away all the other many manufactures I have worked on leading up to 1934.

Stay tuned.

Jon

[mike hadley]

Jon;

The scott was my first adventure into an American set, the radio's here in the uk seem really basic, because of the tube tax at the time (anything up to 67%) and the British Valve Association imposing a levy on tube sockets we ended up with a four tube lineup,really basic in comparison.

Even so this was not without it's faults, sometimes you could be chasing your tail for days locating faults.

As for the scott, well it blows the competition away mine was an involved restoration, speaker voice coil and cone, power transformer, several tubes and a total recap where it had been "restored" before, all well worth it

Mike

[Jon Ketron]

The tuner chassis is now complete.  All resistors tested within a 20 percent tolerance.  Both large ceramic resistors also test within spec.  All original capacitors have been by-passed with brand new caps minus the three capacitors that share inductors along the back of the chassis underside.  There are three of these caps in the circuit Mike mentioned.  After a safe power-up with no shorts utilizing a dim-bulb testing device, monitoring a normal wattage consumption, and checking of the original capacitors, I have deemed to not change out these capacitors at this time due to their placement in the circuit.  I never leave original caps installed on any of my restorations.  This being one exception due to the quality of bathtub cap Scott used during this time frame.  I am not able to test leakage of each due to the inductor installed across the capacitor.  After a 6 hour test on the bench monitoring the wattage consumption I feel comfortable with this decision at this time.  I might go back in at a later date depending if the customer decides he wants both chassis re-stuffed with new parts.  This is another reason I used pure silicon for placement of new caps.

With that said, my analysis on performance:  This AW15, being my first ever one worked on and listened to, has outstanding performance in all areas expected in a receiver of this vintage.  This set exceeds quality on all levels compared to other manufactures of the time.  I am hooked for sure!  Selectivity and sensitivity are unmatched compared to those manufactures worked on in the past of the same time frame: RCA, Zenith, Philco, Atwater Kent etc....  The AW15 has zero inference from anything due to full shielding.  With the antenna disconnected, the unit is dead quiet, that is how good the shielding is.  Amazing!

This unit performs better than my amateur radio receivers from the same time period.  I tuned in 40 meter's just a bit ago on the AW15 and used the BFO push button to decipher CW and SSB.  Tuning in 40M on a 20 ft. long wire inside the house is amazing as I can only receive this area of the spectrum on my 80 ft. outside antenna.  Atmospheric conditions also play into this performance.  None of the other receivers I own that have a BFO can achieve this with an indoor antenna close to noon Eastern time!  Must be those three I.F. stages utilized in the circuit.  Amazing technology for 1934!

 

Utilizing the standard broadcast band, fidelity for AM is superb.  Tonal range is phenomenal, especially when I fun period music through my SSTRAN low power transmitter.  Bass is powerful, as is the treble.  Just as E.H. Scott literature I have read from this time period stated!

Everything works like it did from the factory.  Most of the radio tubes utilized in this set are of the Arcturus brand and have an engraved "L" on the bottom of them.  I placed each one back in it's original spot, carefully noting where each one originally went after I brought the receiver in for servicing.  Can anyone shed more light on the "L" engraving.  Does this stand for laboratory?  All tubes on the tuner chassis minus two are "L" engraved Arcturus tubes.  I understand E.H. Scott hand selected tubes.  Amp tubes are of a different brand and not engraved.

Thanks to all whom helped on this restoration!  Special thanks to Norman for supplying me with a new gear box.  Thank you all for teaching me more about Scott.  E.H. Scott and Capehart cannot be beat in terms of quality electronics during the 1930's.  McMurdo and Lincoln are right up there too.  On top of my current two Scott's in the collection which will hopefully grow, my customer has a 30 tube Philharmonic Laureate Grand with remote control and a custom cabinet Phantom I will eventually electrically restore to original operating condition.  More projects to come soon!

Jon

[David C. Poland]

Jon,  Just viewed your u-tube video of your restored set in  operation (link on Antique Radio Forum).

Seems your right side control is a tone control - cutting higher frequency audio?

My AW-15's - the right control is a sensitivity control - early Wunderlick set is 5 step, later set is 3 step).

What does your escutcheon say?

[Jon Ketron]

Dave, thank you for your input on the set.  The escutcheon says "Static".  I would imagine this is the static control. It works great, I can tell a significant difference when receiving a weak station with interference.  The potentiometer is a continuous roll type, no step.  No numbers on the escutcheon as well, I have seen what you are talking about on other variations.  Could this be one of the earliest versions off the line when new?

Jon

[mike hadley]

Jon,

For what it's worth my aw15 also has the same static control, looking at the circuit it is little more than a top cut, variable resistor and a cap to cut hf.

My fifteen is a four post type with wunderlich detector, I have attached a photo of the control,

after a discussion with Kent it would seem that my chassis is somewhere around may to june 1934, I would like to clarify this as it seems to have a mixture of early and late sets, maybe Dave would know more.

I also see from your photo that you have the dual gang volume pot, this appears to be an attempt at local distant control as the second half of the pot varies screen grid voltage along the if strip, this would be a real pain to replace as it has odd values by today's standard ranges.

Good ol E.H. for modifying during production.

oh btw it is a Tasman cabinet

[David C. Poland]

Scott kept changing the circuit associated with the "STATIC" or "SENSTITIVITY" control of the AW-15 series.

My  Wunderlick AW-15 cals it a "Sensitivity" control, 5 step with numbers 1 to 5 on the top of the escutcheon.

My other early AW-15 (factory (?) conversion to 55 tube) says "Static" like Mike pictures above, and is 3 step.

My later AW-15 (55 tube and one antenna post) also says "Static" and is 3 step.

The controls on my AW-15's affect the sensitivity of the IF amp, but in an evolving manner.

Jon - Your set with the dual pot for volume evidently matches the April 10, 1937 diagram. I have no experience with your version. But looking at the 4/10/37 diagram, the 2nd pot of the volume control appeared to affect sensitivity. I note yours has no tone control on the back left corner of the chassis like my AW-15s do. Appears your "Static'  control is a pot in series with a .05 cap  off the plate of the 1st AF tube like a typical tone control, cutting high frequency audio - which would reduce the higher frequency where much of static is heard and is what I observed on your video.

Hence - the observation the AW-15 has the most complex evolution of any Scott model series. We have 5 diagrams so far, but have observed at least 7 variations among a group of collectors at a point a few years ago.

I have had the experience of needing two AW-15 diagrams for referral during a restoration in order to deal with the chassis on my work bench.

Looks like you did a good restoration on yours.

[mike hadley]

Dave;
It would be interesting to know just how many variants of the aw15 were actually made, it seems that no two sets were alike,
Like johns chassis mine has no rear tone control,
it does have the dual pot on the volume control, the static control is a continuous 'top cut', and it has an antenna switch fitted.
My chassis has this odd business with no bathtub filter on the first if, instead there is a discreet choke and 0.1uf cap to ground,
The psu is a 240v version, and it does have the correct Jensen loudspeaker.
I do like the fact that Jon's chassis is in excellent condition, I am rather envious about that as mine has been stored badly and has rust,
I must commend Jon on his restoration, as Scott radios are something special.

[Jon Ketron]

Thank you Dave for the comments on the restoration.  Throughout this restoration, there were many occasions I had to guess or research the component in question on the tuner chassis.  The early schematic I have for this unit shows a 2A7 in circuit.  No 2A7 exist and 58's/56's are what run just about everything minus the Wunderlick.  The early AW15 I own in a Tasman has a 5 position switch just like one of yours.  So many variations.  It is interesting to document these.  I am glad you asked about the control on this unit, another variation documented if not already!

Jon
 
David C. Poland said:

Scott kept changing the circuit associated with the "STATIC" or "SENSTITIVITY" control of the AW-15 series.

My  Wunderlick AW-15 cals it a "Sensitivity" control, 5 step with numbers 1 to 5 on the top of the escutcheon.

My other early AW-15 (factory (?) conversion to 55 tube) says "Static" like Mike pictures above, and is 3 step.

My later AW-15 (55 tube and one antenna post) also says "Static" and is 3 step.

The controls on my AW-15's affect the sensitivity of the IF amp, but in an evolving manner.

Jon - Your set with the dual pot for volume evidently matches the April 10, 1937 diagram. I have no experience with your version. But looking at the 4/10/37 diagram, the 2nd pot of the volume control appeared to affect sensitivity. I note yours has no tone control on the back left corner of the chassis like my AW-15s do. Appears your "Static'  control is a pot in series with a .05 cap  off the plate of the 1st AF tube like a typical tone control, cutting high frequency audio - which would reduce the higher frequency where much of static is heard and is what I observed on your video.

Hence - the observation the AW-15 has the most complex evolution of any Scott model series. We have 5 diagrams so far, but have observed at least 7 variations among a group of collectors at a point a few years ago.

I have had the experience of needing two AW-15 diagrams for referral during a restoration in order to deal with the chassis on my work bench.

Looks like you did a good restoration on yours.