Electrical Engineering/Schmatic question


I am trying to decipher a schematic on a tube amp from a 1947 jukebox.
Following the connections from a 4 prong jones plug socket I see that it leads to a transformer and to some tubes.  It also branches off to to up arrows marked "A" and "B", and idea what that means?  If not do you know of any site I might post this question on?  


ANSWER: I searched for 1947 jukebox schematic diagrams and found a number of them listed at various websites.  You should search around a little deeper knowing, of course, make/model.

There is likely no manufacturer support for something this old; your only chance is a hobbyist or collector who has saved old manuals, etc.

If you could give me the make and model and send a photo of the part/section you explained in your question I might be able to give you an educated guess. However, markings that you explained are nearly always unique to the model and don't follow generic layout and connection diagrams.

I will await your further information and photo(s).


PS:  I did find a few diagrams on google and notice that with old Wurlitzer boxes the A and G designation almost always refer to the Right and Left channel of stereo audio.  In 1947 stereo was not yet a big thing so it may not be so, but it could also be related to channel A or channel B in an audio system for each channel of sound delivery to audio zones in a restaurant, etc.

---------- FOLLOW-UP ----------

QUESTION: Hi Mr. Cleggsan ,
I forgot to provide you with a link of the amp.  It is a Seebrug 147 jukebox, made in 1947.


The Jones Plug is marked P1 on the schmatic.  And you will see that it has two Arrows pointing up, marked A and B.  

Hope this clarifies things.

Thanks again


Got it.

Are you ready?  It's the main power feed.  These two lines feed power to the power transformer which supplies all the dc for the amplifier.

The plugs, P1 and P2 are ancillary for powering up.  Probably something plugs into these two sockets which connect to the main power switch or some external circuit used for activation.

In other words, there is some other circuit or switching for turning on the amplifier not shown on this schematic. There may be another schematic or system diagram showing the start/ON system.

Hope this helps.  

Electrical Engineering

All Answers

Answers by Expert:

Ask Experts




All technical areas of Electronics Engineering.


BSEE, MBA, Design, R&D, University Research.
Senior Life Member of IEEE. Life Fellow of AES.

IEEE, Consumer Electronics Society, Audio Engineering Society.
Broad teaching experience; work experience mostly in consumer electronics and conversion from analog to digital technologies. Pioneer in digital audio at all levels.

BSEE (Equiv) BYU BSEE University of North Dakota MSBA (MBA) Illinois State University Graduate Studies in Computer Science - Bradley University Graduate Studies - Ohio University Graduate Studies - University of Missouri Kansas City DeVry Tech - Electronics

©2017 About.com. All rights reserved.