ELECTRICAL RESTORATION: E.H. SCOTT AC-10

[Jon Ketron]

This restoration topic will cover an electrical restoration of the rare E.H. Scott AC-10 radio set.  Prior to the chrome years, preceding sets including the AC-10 were offered through custom set builders or kits supplied via E.H. Scott (then called Scott Transformer Co.) between the early 1920's through 1930.  While E.H. Scott offered the set to the consumer, they did not offer assembled sets direct due to then current RCA Superhetrodyne patents controlling the sale of the Superhetrodyne circuit.  E.H. Scott would contract through custom set builders (popular at the time) to have these radio units built for the customer.  I find this part of E.H. Scott history fascinating!

Not a cheap set by any means when sold new, the AC-10 was a high quality unit for the time it was introduced to the market.  The AC-10 consists of a tuner chassis, separate power amplifier, and E.H. Scott labeled Rola speaker.  There were several AC-10 versions offered between 1929-1930.  The set shown below is a late version, circa 1930.  Two sets of wiring harnesses connect both tuner and power amp together.  These cabled are already in the works of being replicated to look very close to or near exact copies of the originals.

I find the AC-10 a very attractive set, especially with it's copper coil shield along the back of the tuner.  AC-10's surface from time to time, complete example's are rare to come across from what I have seen within the hobby.  This example shown below is period correct.  Many thanks to the two gentlemen whom have allowed me to acquire the parts to make a complete set.

The cabinet this receiver will be housed in will be discussed in a separate topic you will not want to miss.  More on that later in a separate topic!

Thanks, comments welcome!

Jon

[Jon Ketron]

Rhode Island Wiring Service Inc.    They do amazing work, highly recommended for a custom harness.
 
Robert Feenstra said:

I need to know where you are getting the cloth cover for the cable.  I have not been successful in locating that nice of looking stuff!

[Jon Ketron]

Disassembly of the speaker continues:

[Robert Feenstra]

Thank you!

Jon Ketron said:

Rhode Island Wiring Service Inc.    They do amazing work, highly recommended for a custom harness.
 
Robert Feenstra said:

I need to know where you are getting the cloth cover for the cable.  I have not been successful in locating that nice of looking stuff!

[David C. Poland]

1).  The amp should be placed under the the left side of the receiver, not the right side, to minimize hum.  Source:   The owner instruction booklet  and also Citizens Radio Call Book, Sept 1929, page 132. 

2). Also, the push-pull speaker wiring is a bit different. I am acccustomed to a center tapped output transformer mounted on the speaker with B+ feeding through the center tap to supply the plate voltage.  Not the AC-10  I restored some years ago. The B+ to the output tubes is NOT by a center tap from the transformer on the speaker, Rather there is an "output choke" on the amp that supplies B+  through a center tap  to the ends of the output choke to the two 45 tube plates socket lugs. The plates lugs on the two 45 tube sockets then are also wired to the two speaker terminals on amp terminal strip - at high voltage. The output  transformer in the speaker base has no center tap and just serves feed audio signal from primary to the secondary to the speaker voice. This is actually consistent with the published amp diagrams which fail to show the speaker with it's separate output transformer. 

[Jon Ketron]

Thank you Dave.  This set up will not allow the amp to sit under the tuner due to cabinet construction and placement of chassis and speaker.  Kent King's set up on his Versailles cabinet is of identical configuration to this one.

Jon

[Jon Ketron]

Further disassembly of the speaker continues.  Interesting to note the initials on the field coil!

[Jon Ketron]

After disassembly of the speaker, I drilled out all rivets on the blue E.H. Scott tag as well as the surround ring on the speaker basket.  I did not want to risk damaging the blue tag during paint and rust removal.

Each individual metal part of the speaker was carefully scrubbed clean of all old paint and rust.  All pieces will be re-painted a brown similar to the original color.  Pictured below is the just the basket and surround ring.  Speaker base and field coil cover also looked like this once the removal process was complete.  Such a task ended up taking a week to complete.  I utilized a product called "Evapo-rust" currently on the market.  It is a non toxic formula that will do wonders to anything rusting.  I highly recommend the product!

[Jon Ketron]

After all metal parts dried several days later, I shot each with a high quality brown enameled paint.  This paint may not be an exact match, although I feel it is close to the original color.  This color was judged via other Rola examples I have come across and researched in the past.

[Jon Ketron]

3/4 re-assembled and now polished shown below.  Speaker work took place one month ago.  Paint was cured and ready for polishing prior to this posting.  Rivets have been replaced with polished slotted head screws/lock nuts/nuts.  This is not original hardware to the speaker.  There will be spacers on the output transformer securing screws to allow clearance for the screws holding the blue tag to the speaker base.

[Jon Ketron]

Speaker was sent off with spyder and NOS cone to be re-coned by a good friend of mine.  Cone will be modified to accommodate this Rola speaker.  The NOS cone is a perfect match regarding size and surround. 

I patiently await the final result!

Jon

[John T. Meredith]

This is a very nicely done restoration.  You should be commended on a job very well done.  The early pre-chrome Scott Radios are some of the most beautiful radios made.  The Super 10, SG 9, Symphony, and AC 10 are all desirable Scott Radios.

Cheers,

John Meredith 

[Y2K Bruce]

Jon-Your restorations and photo documentations are wonderful and long term guidelines for future restorers.

Excellent work Sir !!