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Seeburg jukebox MRA1-L6 amplifier schematic?

Vacuuminded

Vacuuminded

New Member
Anybody have a schematic for the above Seeburg amp? It is mono, using four 6V6's. I also have a receiver to work on that mates with it, believe it is for a model 100C box.
If somebody has a used service manual for the C that includes this amp, I would be interested in purchasing it. I hate to buy a brand new one for one lousy schematic, but might have to at this rate..
Thanks,
Chris
 
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Beautiful- I only see one file for that amp, but it is the schematic so we're in business- Thanks!

Holy cheeseballs, they're running those four 6v6's in push-pull parallel!?!? I've heard of that having been done, but have never actual run into it before! This is nutty! Being they are calling this a master/remote amplifier, I just assumed one pair was for the local speakers, the other for the remotes. *BUZZ* Wrong!

Wonder what effect would result if the second pair of 6V6's in that parallel string were simply removed...
 
They ran the 4 6V6 PPP in the 1951 100B model also maybe some others later( I think maybe 54 and up to ?? had 2 6L6 PP)
I had a 100B in high school it would probably work just not well with 2 of them removed
probably not a good idea though might damage the amp, The other chassis was a selection recover that also read the coin acceptor and received playback/record/side selections to control the playback . The amp can run independently from selection receiver.
If has electromagnet speaker that may be needed in the circuit for P/S choke also.
here are the different models
http://www.jukeboxparts.nl/en/Fotogalerij/Seeburg.html
 
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Vacuuminded said:
Beautiful- I only see one file for that amp, but it is the schematic so we're in business- Thanks!

Holy cheeseballs, they're running those four 6v6's in push-pull parallel!?!? I've heard of that having been done, but have never actual run into it before! This is nutty! Being they are calling this a master/remote amplifier, I just assumed one pair was for the local speakers, the other for the remotes. *BUZZ* Wrong!

Wonder what effect would result if the second pair of 6V6's in that parallel string were simply removed...
Click to expand...

The 2 remaining would likely redplate due to excessive current draw.

However, if you were to locate some decent P-P transformers for a pair of 6V6, then you could make it a stereo/dual channel amp.

To replace the electrodynamic speaker, you can run a regular AlNiCo speaker if voice coil impedance is correct, then for the field coil, use a cementitious wirewound power resistor of adequate wattage for the amp based on the data plate. This saves time and money over buying a choke of similar size. Usually the schematic gives a range of DC resistance rather than an inductance value.
 
1) Thanks for the second link complete with parts list- don't know why that one didn't show up in my searches, bt now we're in business!

2) Good points on why a trial run with one pair of th 6v6's removed would be a bad idea. If plate current is adequately limited they shouldn't self destruct, but agreed it like probably be best to just fill all four sockets. Was just a curiosity.

3) Thanks for the dissertation on PM versus field coil speakers, and the power resistor trick. Agree-, for the few times I've had to do just that in antique radios, there seems to be a negligible amount of B+ filtering being done by that coil.

4) This amp will not be hacked up and modded for hi-fi use, I am rebuilding it and the receicer for a Seeburg model C. The only reason I could be modifying it outside of the norm, is if something major like that goofy output transformer is shot.

Thanks again!
Chris
 
I just did a MRA3-L6 ,I had to put a resistor in place of the field col speaker, and supply filament current through the power plug to test it
 
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