Continental AMI Juke Box Fault Finding

[rob1948]

Hi Ron and Norman,
Thank you very much for your response(s). Yes I am going to save the original valve amp and find someone local to check it and re build if necessary. Thanks Guys. Rob

[rob1948]

Hi Norman/Ron, My record magazine is turning abnormally slow. Would that be because the DC magazine motor may need new brushes, or the magazine spindle needs lubrication or both? I have managed to find a local radio repair company that will check my valve amplifier and rebuild/repair if necessary. I took it in today. Thanks Rob

[Ron Rich]

Hi Rob,
Yes to all of the above -- plus- check the voltage being supplied to the motor-- should be between 28 and 32 DC-- Rectifier, or cap, in power supply, may be failing ? Ron Rich

[jukenorman]

Hi Rob,
I wasn't sure whether you had serviced a DC motor; there is a video on You Tube - Rock-Ola motor repair - that you can have a look at. The commentary is in German though, but it will still give you a flavour of what is involved.
Norman.

[Ron Rich]

Hi Norman,
I think you may have gotten your apples confuzzed with oranges ? This is an AMi, not RockOla ! LOL Ron Rich

[jukenorman]

Yes Ron, I was trying to let him see a DC motor being stripped down and it just happened to be a Rock-Ola!
Norman.

[rob1948]

Ron/Norman,
Guys once again thank you for your reply's. Certainly a great help to me. I am going to start with checking the DC voltages as I have a feeling it could be the rectifier/condenser. Will also watch the Rock-Ola DC motor video. Thanks Rob.

[rob1948]

Hi Norman/Ron,
The diode rectifier and 1000 mfd condenser are both in the 'Junction Box'(bottom left hand corner at the rear of the JB). Is there a convenient place to check the DC voltage without removing the Junction Box and testing in the back ? I have also read in some of the posts that guys are replacing the 1000 mfd condenser with bigger ones ? Is this advisable? Thanks Rob

[jukenorman]

Hi Rob,
Jay Hennigan drew out the schematic of the junction box and posted it on his website along with some notes
www.west.net/~jay/jukebox/amijunction.html

As you can see from the schematic, you can check the DC voltage at the four pin socket. You will see that Jay is increasing the value of the electolytic capacitor (in the notes). Modern capacitors are smaller in size than they were in 1960, increasing the value has no downside.

Norman.

[rob1948]

Thank you Norman. I will go to Jay's website.

[rob1948]

Hi Norman, All sorted I have 30V DC so so we have eliminated that problem. Must be the motor requiring a service and/or serious lubrication of the Magazine trunnion required. The current lubrication or grease may have hardened or lost its viscosity ? Thanks Rob

[rob1948]

Hi Norman/Ron,
Although I have measured 30V DC from the Junction Box with no load, if the rectifiers and or condenser are failing as Ron pointed out then maybe under load the voltage is dropping below the required 28V resulting in the slow rotation of the magazine. Could this be the problem ? If so it may be worth my while replacing the rectifier and condenser, over and above servicing the DC motor? What do you think ?? Thanks Rob

[Ron Rich]

Hi Rob,
Yes--measure it with a load-- If low, then, I would suspect the cap is failing--- Ron Rich

[jukenorman]

Alternatively if the motor isn't as free as it might be, it might be taking too much current resulting in the voltage being pulled down - a bit catch 22, I'm afraid! I think the motor not being 100% is one of the reasons that increasing the size of the capacitor brings an improvement.
Norman.

[Ron Rich]

Oh, That sure could be-- I always use a 1000, but then I always clean/oil the motors too before I attempt to run it--- Ron Rich