• Year
  • 1939
  • Category
  • Sound/Video Recorder and/or Player
  • Radiomuseum.org ID
  • 274422

 Technical Specifications

  • Number of Tubes
  • 4
  • Main principle
  • Audio-Amplification
  • Wave bands
  • - without
  • Details
  • Jukebox-Coin operated Phonograph
  • Power type and voltage
  • Alternating Current supply (AC) / 115 Volt
  • Loudspeaker
  • Electro Magnetic Dynamic LS (moving-coil with field excitation coil)
  • from Radiomuseum.org
  • Model: Jukebox DE-39 - Rock-Ola Manufacturing
  • Author
  • Model page created by Craig Andrews. See "Data change" for further contributors.

 Collections | Museums | Literature

Collections

The model Jukebox DE-39 is part of the collections of the following members.

 Forum

Forum contributions about this model: Rock-Ola: Jukebox DE-39

Threads: 1 | Posts: 1

In '39 Rock-Ola stapled the system and amplifier schematics onto the inside of the back door.  Sadly, these are not present on my jukebox so i am working off a Rock-Ola amplifier model F-2 photograph of a schematic that i found online.  For the most part, this schematic agrees with my amplifier so i am pretty much taking it as gospel. 

However, today I have been examining the volume control and things just weren't coming together in my mind so i pulled the amp and flipped it over to see what was going on.  There is a mistake in the schematic and the wiper is not shown at all.  At first I thought they were sloppy and showing the wiper on the capacitor as a filled circle rather than an arrow, but that was not making a lot of sense either.  As it turns out, this is a 4-terminal pot and the tone control capacitor is indeed on a tap.  The grid of the 76 is connected to the wiper and not directly to the high side of the pot as incorrectly shown in the schematic.  So for future reference, put an X through the line from the high side of the pot to the grid, add in a wiper to the pot, connect the wiper to the grid of the 76, and sleep a little better tonight for setting the world straight.

Currosity got me to pull up the E series of the amplifier that is found on the ST39 page.  Hmmm...... on this schematic they are showing the tone control condenser as a non-descript, mixed-breed open circle / arrow mongrel, and they are still not showing a clear indication of a wiper connected to the grid of the 76.  The schematic gets a little spotty in this region, but on the input to the grid there is a black terminal circle with a voltage nearby and on the left side of this circle it could be seen as an arrow towards the high side of the pot.

How do you suppose that this mistake could made it through a number of revisions of the schematic?  Didn't someone ever look at the do-nothing pot in the F-2 schematic and wonder?

So can someone that has the model E amplifier let me know what is actually there?

Hope someone, at some time, finds this little tidbit useful.

-Craig

 

Rock-Ola DE-39 YouTube

Attachments

Craig Andrews, 25.Oct.15

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