Need Help Identifying E.H. Scott Amp/PS Chassis

[Ben Hase]

I picked up a large E.H. Scott chassis among some other pieces of tube equipment this past weekend. The original owner said that he thought it came from a Philharmonic but some things are not lining up. The power transformer is Black and it has rectangular multi-pin interconnect sockets. Tube compliment is (2) 5U4, (4) 6L6, output TX is marked. I also have an external crossover chassis. Images to follow shortly. 

[Ben Hase]

Pics...

[Norman S Braithwaite]

You have the power amplifier from an AM-FM Phantom produced very shortly before WWII when chrome was a material in demand for the war time effort.

Norman

[Ben Hase]

Norman, 

Looking at the Phantom schematic, it only shows (2) 6L6. This chassis is marked 6L6 on all four sockets... Is it possible its a late production Philharmonic?

[Kent King]

Ben -

That is a possibility. I have seen one or two very late Philharmonic sets with a similar amplifier. Since it shows 4 6L6s on the sockets, it is probably a Philly amp. 

Kent

[Norman S Braithwaite]

Indeed it is a very late Philharmonic amp. I had only seen the black transformers on the lesser models before. With modification it will work for your tuner.

Norman

[David C. Poland]

Agree - a very late production amp/power supply for a Philharmonic.

Does the crossover have a rectifier tube? If so, then the correct tweeters have field coils and suggests perhaps early 1942 production. The outboard crossover uses all 8 ohm speaker set, instead of the standard single 38 ohm large speaker.

[Ben Hase]

Here is a picture of the crossover. I have not opened it up yet but I doubt it has a tube inside. The piece on the side is a dummy plug that must short two of the pins. I plan to clean everything up and test all of the transformers this weekend. Semichrome should be fine on the chassis I would assume?

[David C. Poland]

You have a late version crossover for the optional speaker system. The early version is larger and the crossover uses a different style crossover coils (and has no provision for a rectifier tube). Designed for 8 ohm speakers.

The plug on the end of your crossover is intended for a remote speaker if desired. Just replace the internal jumper with the twin lead to a permanent magnet remote speaker. Either way, the Aux plug must be inserted in the crossover socket for the primary speakers to play.

The 2 pin sockets on the side are for 1 or 2 PM tweeters.

You will find that there is a straight thru of the B+ only to the main speaker field coil via the 5 pin socket. The other 3 pins connect to the crossover's output transformer. Your version is intended for permanent magnet tweeters. 

The smaller cable from the crossover with a small 4 pin plug fits a small socket on the back of the receiver (and then to a wafer on the band switch) to control the tweeters being "on" for FM only, 

******

The "knock out" in the middle of your example  between the transformers is where the 35Z3 rectifier would sit to power tweeter field coil(s) for 1) a single tweeter (Scott Laureate) or 2) a tweeter pair (Philharmonic or Phantom using 6L6 output tubes).) See the diagrams in Riders, Vol 14 under Scott page pg 14-15 and additional detail page 12. The rectifier version crossover has 4 pin sockets for the field coil tweeters.

The use of Jones plugs seems to have been a late 1941 change. My Scott Laureate uses the Jones plug crossover with rectifier for the single field coil tweeter center mounted in the 15 inch speaker cone (thus a co-axial arrangement). And I just acquired  from a late version FM Phantom,  a complete optional 4 unit system consisting of Jones Plug type cable, 15 inch main speaker, crossover with rectifier,  pair of field coil tweeters and the small set cable for tweeter control.

*****

I have never seen any Philharmonic (nor Phantom) diagrams showing Jones plug cabling. To help understand Jones plug  wiring of your amp's sockets,  refer to the Scott Laureate model diagram, Volume 14 - page 29-30 and revised Volume 15 page 5.  And trace your Philharmonic amp for comparison. But be aware however, the Laureate output 6L6's are located on the receiver chassis. In contrast, the Phantom and Philharmonic receivers have earlier audio stage tubes and the amp has the output 6L6 output tubes - so the Laureate Jones plug wiring shown is a bit different regard to the audio circuit and C- bias. 

With regard to the Jones plug speaker systems, it appears (but I have not fully explored) that the outboard  crossover based 3 and 4 unit optional speaker systems are inter-changeable between the Laureate, Philharmonic and Phantoms with 6L6 output tubes. 

I have the dubious project to mate an Jones socket amp like yours to an old style round plug cable for a  BOL Philharmonic with remote control. I have made a Jones plug conversion cable with a 7 pin socket for the receiver cable. The typical 7 pin socket will not accept the set cable plug, however. But the right 7 pin tube tester socket will. 

[Ben Hase]

David, 

Thank you for all of the great information. The Laureate tip will definitely help out during testing.

These pieces will be up for grabs. If I can find a buyer here or on another radio collectors forum that would be awesome but I may also list them on eBay. In your experience would it be more desirable for a buyer to receive both the Amp/PS and Crossover?

[David C. Poland]

I slightly favor separate sales.

[Ben Hase]

Cool.

I will post test results later this week. I got some very low initial DCR readings on the rectifier and output filaments of the PT so I definitely want to run some AC through it. If anyone is interested in these pieces please send a PM> 

[David C. Poland]

if rectifiers are installed, do not power the amp up without a speaker field coil (or equivalent) load, and at that, stay less than full house voltage with a Variac. Do not trust the original filter condensers. Without the proper electrical load, the B+ voltages will go higher than intended.

The toggle switch on the side of the amp is a high/low switch to change the power transformer primary for above or below 115 volt house AC. Have the toggle up to lower B+ and filament voltages.