Masterpiece repair project

[Randy Rago]

I'm a member / restorer at the Asheville Radio Museum avlradiomusem.org and recently connected with a customer asking to restore a relative's Sott Masterpiece.

Been in the tube radio fixin' hobby since the early 70's and never came across one of these and saw a once-in- a -lifetime opportunity so of course I said YES!

From what i can tell, its mostly there but I have one question for the group. I have to re-cone the speaker but it has a 14 ohm VC, not the 38 ohm i've read about here. What are my issues if i run it with the14 ohm VC? THX

[David C. Poland]

the Masterpiece audio upgrade was a pair of push-pull 6J5 drivers instead of a single 6J5 driver.

[Randy Rago]

What are the dual 6v6's in the power amplifier for?

[David C. Poland]

the pair of 6V6 tubes on the power supply are the final amplifier output tubes. 

[Don Jackson]

David, my set was also missing the speaker. I made an adapter using a Hammond 125E transformer so I can use an 8 ohm permanent magnet speaker. I understand the same speaker was used in the early Phantom and Sixteen sets. So if I ever came across a Scott branded speaker like the one shown in your photo and it had an octal plug would it be the correct one? Were there any Scott speakers that had an octal plug that would not be compatible?

[David C. Poland]

Yes. The 12 inch Magnavox speaker with Scott decal having the 8 pin octal cable plug is for the Masterpiece, early 19 tube Phantom and model Sixteen (and the 18 tube varient) and is the only Scott speaker with the octal 8 pin plug. To verify, take resistance readings to assure a match for 2 field coils and output transformer, lest someone has put an octal plug on some other speaker.

The closest look alike is the Super 12 model single field coil 12 inch Scott Magavox speaker with the 5 pin plug. It lacks the 2nd field coil. It has the same silver crackle paint and is also flange mount.

The other possible to avoid be the 12 inch speaker for the 1940-41 optional high fidelity multi speaker system for the Phantom Deluxe, but that speaker says "high fidelity" on the bell cover, a single field coil and a small 5 pin plug that only fits the outboard crossover.

[Don Jackson]

Thanks for confirming this, the octal plug makes it easy to identify this speaker. Unless someone might have put an octal plug on another speaker, as you suggest. I would definitely want to verify the resistance readings. 

[David C. Poland]

Don - when you find the correct speaker, there is a chance the output transformer primary may be half open ( I was batting about 50% on the those I have had). Your Hammond 125-E is the same I used for a replacement years ago. To adjust it for the 38 ohm voicemail, I added 25 turns of wire around the core from the secondary #6 lug to make a #7 lug. Purpose was to decrease the ratio of primary to secondary using lugs 1 and 7. This reduced ratio is in keeping with a good output transformer that I measured out.