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 Post subject: Seeburg 100-C Jukebox has Static
PostPosted: Feb Sun 03, 2019 9:15 pm 
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I've got a an M100-C ("Select-o-Matic") jukebox (circa 1959) with a static problem.

It's been fine for a year or so but now has this problem. When you first power it up and select a record the amp comes on, record mech starts spinning, and the carriage scans for he selection. While the motor is turning a background static starts to build after a few seconds and continues until you shut down the machine.

Sounds like a bad ground connection, or perhaps a volume, bass, or treble control issue?

Not sure on the history of tube replacement.


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Tue 05, 2019 2:35 am 
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Location: Beaver Falls, PA. USA
Has the amplifier been restored? It could be a capacitor breaking down.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Tue 05, 2019 4:02 am 
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Tim,

I'm not sure if the mp has ever been restored but I'll take a look and see if I can tell. I guess it would have newer-looking components if it has been.

I'll clean the volume and tone controls and try to determine if it's them as well.

Thanks.


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Tue 05, 2019 3:51 pm 
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The M100C dates back to 1952, not 1959. It sounds like an amplifier malfunction to me. Leaky capacitors, bad tubes...the usual.

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Antique Radio Club of Illinois


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Tue 05, 2019 4:15 pm 
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Thanks, John. Yes -- you are correct about the date.

I haven't looked at the amp yet but sounds like a rebuild would solve it. I've never done that but I'm pretty good with most things electrical, just not audio tube amps. If I get a rebuild kit is it pretty straightforward? My weakness would be in troubleshooting if something goes wrong!


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Wed 06, 2019 1:00 pm 
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You may want to start with the easy things first. Maybe try cleaning tube sockets, one at a time. You will probably have to do that eventually and it is the least invasive thing to do first.

Often a source of static.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Wed 06, 2019 9:19 pm 
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Location: Boston, MA USA
Often a source of static is a failing capacitor. Trying to play the jukebox in this condition may cost you the output transformer. I would replace at least the electrolytic filter capacitors and the output stage grid coupling capacitors before applying power again.

-David


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Thu 07, 2019 12:25 am 
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Yes, all of the capacitors should be replaced. Seeburg used molded John Fast and Tiny Chief capacitors, all of which will be leaky now.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Thu 07, 2019 1:12 pm 
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Did I read correctly that the static is only present when the record mechanism is spinning? It may be a bad ground in the motor wiring, or perhaps there is a noise suppressor of some kind that "isn't". Even a bad ground on a shielded audio wire could cause this ... short and/or disconnect the input to the amp and see if the static is still there. That may narrow it down to either the amp, or something external. Or it may not lol. But it's a start.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Thu 07, 2019 11:31 pm 
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Old Seeburg jukeboxes with tube amps keep the amplifier filaments lit from a winding on the control unit transformer, as long as the box is turned on. When the motor starts, 120vac is applied to the amplifier power transformer, and the 5U4 starts heating; this powers up the amplifier in a matter of seconds.

For bench testing one of those amps, you have to supply 6.3 volts to the filaments from an external source.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Fri 08, 2019 5:47 pm 
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The static seemed to build as the motor started and turned for few seconds. Based on Tim's reply I'm thinking it has nothing to to d=with static buildup and more to do with the delay in the amp getting fully heated. So the static just seems to be a constant issue whenever the amp is working normally.

Looking into getting a rebuild kit (I don't think they are too expensive) and replacing all components. My audio amp troubleshooting skills are not good enough to narrow down a single malfunctioning component.

Keith


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Sun 10, 2019 6:08 am 
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dberman51 wrote:
Often a source of static is a failing capacitor. Trying to play the jukebox in this condition may cost you the output transformer. I would replace at least the electrolytic filter capacitors and the output stage grid coupling capacitors before applying power again.

-David

funny to mention that. I know of a situation where a jukebox was playing perfectly, unrestored of course.

after a few crackles and pops, the magic smoke suddenly and completely engulfed the room. the first filter messed the bed and cooked a large sized power transformer.

thinking the rectifier tube was defective because of the fireworks and light show within its envelope during this massive meltdown, the rectifier tube was replaced, the jukebox was fired up again, and more smoke filled the room.

those poor tubes :shock:

steve

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Sun 10, 2019 3:26 pm 
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THE HORROR!


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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Sun 10, 2019 11:15 pm 
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One thing to remember is that the 1950s Seeburg jukeboxes with the Tormat memory unit have a tube-type control unit with its own power supply, which also needs to be recapped. That unit is easy to spot, as it has two glowing 0A2 regulator tubes.

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 Post subject: Re: Seeburg 100-C Jukebox has Static
PostPosted: Feb Mon 11, 2019 10:10 pm 
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Location: Boston, MA USA
Not so easy to spot is the capacitor inside the small core read-out amplifier chassis (with 12AX7). But the 100C came before the Tormat.

-David


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